diff --git a/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/BlogPostLister.cs b/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/BlogPostLister.cs
index 0ee12943dd..a1d942f71a 100644
--- a/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/BlogPostLister.cs
+++ b/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/BlogPostLister.cs
@@ -30,7 +30,7 @@ namespace AbpDesk.ConsoleDemo
                 //blog.Comments.Add(new BlogPostComment("@john", "good post! " + DateTime.Now.ToString(CultureInfo.InvariantCulture), star: (byte)RandomHelper.GetRandom(1, 6)));
                 //_blogPostRepository.Update(blog);
 
-                //_blogPostRepository.Insert(new BlogPost("Hello World 3!", DateTime.Now.ToString(CultureInfo.InvariantCulture)));
+                //_blogPostRepository.Insert(new BlogPost("Hello World 1!", DateTime.Now.ToString(CultureInfo.InvariantCulture)));
 
                 foreach (var blogPost in _blogPostRepository)
                 {
diff --git a/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/Program.cs b/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/Program.cs
index 45555e2303..77941a273f 100644
--- a/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/Program.cs
+++ b/src/AbpDesk/AbpDesk.ConsoleDemo/AbpDesk/ConsoleDemo/Program.cs
@@ -26,12 +26,6 @@ namespace AbpDesk.ConsoleDemo
                 Console.WriteLine("Press ENTER to run again...");
                 Console.ReadLine();
 
-                RunDemo(application);
-
-                Console.WriteLine();
-                Console.WriteLine("Press ENTER to exit...");
-                Console.ReadLine();
-
                 application.Shutdown();
             }
         }
diff --git a/src/AbpDesk/AbpDesk.MongoBlog/AbpDesk/Blogging/BlogPost.cs b/src/AbpDesk/AbpDesk.MongoBlog/AbpDesk/Blogging/BlogPost.cs
index 1980503505..058dc3ccce 100644
--- a/src/AbpDesk/AbpDesk.MongoBlog/AbpDesk/Blogging/BlogPost.cs
+++ b/src/AbpDesk/AbpDesk.MongoBlog/AbpDesk/Blogging/BlogPost.cs
@@ -22,7 +22,7 @@ namespace AbpDesk.Blogging
 
         public BlogPost([NotNull] string title, [NotNull] string body)
         {
-            Id = Guid.NewGuid().ToString("D");
+            Id = Guid.NewGuid(); //TODO: Get from ctor!
 
             Check.NotNull(title, nameof(title));
             Check.NotNull(body, nameof(body));
diff --git a/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/EfCoreRepository.cs b/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/EfCoreRepository.cs
index 8cb88d38f0..06471c6ecc 100644
--- a/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/EfCoreRepository.cs
+++ b/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/EfCoreRepository.cs
@@ -9,9 +9,9 @@ using Volo.Abp.EntityFrameworkCore;
 
 namespace Volo.Abp.Domain.Repositories.EntityFrameworkCore
 {
-    public class EfCoreRepository<TDbContext, TEntity> : EfCoreRepository<TDbContext, TEntity, string>, IEfCoreRepository<TEntity>
+    public class EfCoreRepository<TDbContext, TEntity> : EfCoreRepository<TDbContext, TEntity, Guid>, IEfCoreRepository<TEntity>
         where TDbContext : AbpDbContext<TDbContext>
-        where TEntity : class, IEntity<string>
+        where TEntity : class, IEntity<Guid>
     {
         public EfCoreRepository(IDbContextProvider<TDbContext> dbContextProvider)
             : base(dbContextProvider)
diff --git a/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/IEfCoreRepository.cs b/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/IEfCoreRepository.cs
index 38d083dac7..e7e6ab171f 100644
--- a/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/IEfCoreRepository.cs
+++ b/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/IEfCoreRepository.cs
@@ -1,10 +1,11 @@
+using System;
 using Microsoft.EntityFrameworkCore;
 using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Domain.Repositories.EntityFrameworkCore
 {
-    public interface IEfCoreRepository<TEntity> : IEfCoreRepository<TEntity, string>, IQueryableRepository<TEntity>
-        where TEntity : class, IEntity<string>
+    public interface IEfCoreRepository<TEntity> : IEfCoreRepository<TEntity, Guid>, IQueryableRepository<TEntity>
+        where TEntity : class, IEntity<Guid>
     {
         
     }
diff --git a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.Designer.cs b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.Designer.cs
similarity index 87%
rename from src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.Designer.cs
rename to src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.Designer.cs
index 9bf48b52ba..e54095b147 100644
--- a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.Designer.cs
+++ b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.Designer.cs
@@ -8,8 +8,8 @@ using Volo.Abp.Identity.EntityFrameworkCore;
 namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 {
     [DbContext(typeof(IdentityDbContext))]
-    [Migration("20161221194225_AbpIdentity_Initial_Migration")]
-    partial class AbpIdentity_Initial_Migration
+    [Migration("20170119175536_Initial_Abp_Identity")]
+    partial class Initial_Abp_Identity
     {
         protected override void BuildTargetModel(ModelBuilder modelBuilder)
         {
@@ -19,7 +19,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityRole", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ConcurrencyStamp")
@@ -42,15 +42,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityRoleClaim", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ClaimType");
 
                     b.Property<string>("ClaimValue");
 
-                    b.Property<string>("RoleId")
-                        .IsRequired();
+                    b.Property<Guid>("RoleId");
 
                     b.HasKey("Id");
 
@@ -61,7 +60,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUser", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<int>("AccessFailedCount");
@@ -111,15 +110,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserClaim", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ClaimType");
 
                     b.Property<string>("ClaimValue");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -130,7 +128,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserLogin", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("LoginProvider");
@@ -139,8 +137,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
                     b.Property<string>("ProviderKey");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -152,14 +149,12 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserRole", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
-                    b.Property<string>("RoleId")
-                        .IsRequired();
+                    b.Property<Guid>("RoleId");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -173,15 +168,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserToken", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("LoginProvider");
 
                     b.Property<string>("Name");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.Property<string>("Value");
 
diff --git a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.cs b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.cs
similarity index 89%
rename from src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.cs
rename to src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.cs
index 95ecb64937..d52557901e 100644
--- a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20161221194225_AbpIdentity_Initial_Migration.cs
+++ b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/20170119175536_Initial_Abp_Identity.cs
@@ -4,7 +4,7 @@ using Microsoft.EntityFrameworkCore.Migrations;
 
 namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 {
-    public partial class AbpIdentity_Initial_Migration : Migration
+    public partial class Initial_Abp_Identity : Migration
     {
         protected override void Up(MigrationBuilder migrationBuilder)
         {
@@ -12,7 +12,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityRoles",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
+                    Id = table.Column<Guid>(nullable: false),
                     ConcurrencyStamp = table.Column<string>(nullable: true),
                     Name = table.Column<string>(maxLength: 256, nullable: true),
                     NormalizedName = table.Column<string>(maxLength: 256, nullable: true)
@@ -26,20 +26,20 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityUsers",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
-                    AccessFailedCount = table.Column<int>(nullable: false, defaultValue: 0),
+                    Id = table.Column<Guid>(nullable: false),
+                    AccessFailedCount = table.Column<int>(nullable: false),
                     ConcurrencyStamp = table.Column<string>(nullable: true),
                     Email = table.Column<string>(maxLength: 256, nullable: true),
-                    EmailConfirmed = table.Column<bool>(nullable: false, defaultValue: false),
-                    LockoutEnabled = table.Column<bool>(nullable: false, defaultValue: false),
+                    EmailConfirmed = table.Column<bool>(nullable: false),
+                    LockoutEnabled = table.Column<bool>(nullable: false),
                     LockoutEnd = table.Column<DateTimeOffset>(nullable: true),
                     NormalizedEmail = table.Column<string>(maxLength: 256, nullable: true),
                     NormalizedUserName = table.Column<string>(maxLength: 256, nullable: true),
                     PasswordHash = table.Column<string>(nullable: true),
                     PhoneNumber = table.Column<string>(nullable: true),
-                    PhoneNumberConfirmed = table.Column<bool>(nullable: false, defaultValue: false),
+                    PhoneNumberConfirmed = table.Column<bool>(nullable: false),
                     SecurityStamp = table.Column<string>(nullable: true),
-                    TwoFactorEnabled = table.Column<bool>(nullable: false, defaultValue: false),
+                    TwoFactorEnabled = table.Column<bool>(nullable: false),
                     UserName = table.Column<string>(maxLength: 256, nullable: true)
                 },
                 constraints: table =>
@@ -51,10 +51,10 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityRoleClaims",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
+                    Id = table.Column<Guid>(nullable: false),
                     ClaimType = table.Column<string>(nullable: true),
                     ClaimValue = table.Column<string>(nullable: true),
-                    RoleId = table.Column<string>(nullable: false)
+                    RoleId = table.Column<Guid>(nullable: false)
                 },
                 constraints: table =>
                 {
@@ -71,10 +71,10 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityUserClaims",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
+                    Id = table.Column<Guid>(nullable: false),
                     ClaimType = table.Column<string>(nullable: true),
                     ClaimValue = table.Column<string>(nullable: true),
-                    UserId = table.Column<string>(nullable: false)
+                    UserId = table.Column<Guid>(nullable: false)
                 },
                 constraints: table =>
                 {
@@ -91,11 +91,11 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityUserLogins",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
+                    Id = table.Column<Guid>(nullable: false),
                     LoginProvider = table.Column<string>(nullable: true),
                     ProviderDisplayName = table.Column<string>(nullable: true),
                     ProviderKey = table.Column<string>(nullable: true),
-                    UserId = table.Column<string>(nullable: false)
+                    UserId = table.Column<Guid>(nullable: false)
                 },
                 constraints: table =>
                 {
@@ -112,9 +112,9 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityUserRoles",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
-                    RoleId = table.Column<string>(nullable: false),
-                    UserId = table.Column<string>(nullable: false)
+                    Id = table.Column<Guid>(nullable: false),
+                    RoleId = table.Column<Guid>(nullable: false),
+                    UserId = table.Column<Guid>(nullable: false)
                 },
                 constraints: table =>
                 {
@@ -137,10 +137,10 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
                 name: "IdentityUserTokens",
                 columns: table => new
                 {
-                    Id = table.Column<string>(nullable: false),
+                    Id = table.Column<Guid>(nullable: false),
                     LoginProvider = table.Column<string>(nullable: true),
                     Name = table.Column<string>(nullable: true),
-                    UserId = table.Column<string>(nullable: false),
+                    UserId = table.Column<Guid>(nullable: false),
                     Value = table.Column<string>(nullable: true)
                 },
                 constraints: table =>
diff --git a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/IdentityDbContextModelSnapshot.cs b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/IdentityDbContextModelSnapshot.cs
index 5a86b97493..762d4a55c3 100644
--- a/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/IdentityDbContextModelSnapshot.cs
+++ b/src/Volo.Abp.Identity.EntityFrameworkCore/Migrations/IdentityDbContextModelSnapshot.cs
@@ -18,7 +18,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityRole", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ConcurrencyStamp")
@@ -41,15 +41,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityRoleClaim", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ClaimType");
 
                     b.Property<string>("ClaimValue");
 
-                    b.Property<string>("RoleId")
-                        .IsRequired();
+                    b.Property<Guid>("RoleId");
 
                     b.HasKey("Id");
 
@@ -60,7 +59,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUser", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<int>("AccessFailedCount");
@@ -110,15 +109,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserClaim", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("ClaimType");
 
                     b.Property<string>("ClaimValue");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -129,7 +127,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserLogin", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("LoginProvider");
@@ -138,8 +136,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
                     b.Property<string>("ProviderKey");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -151,14 +148,12 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserRole", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
-                    b.Property<string>("RoleId")
-                        .IsRequired();
+                    b.Property<Guid>("RoleId");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.HasKey("Id");
 
@@ -172,15 +167,14 @@ namespace Volo.Abp.Identity.EntityFrameworkCore.Migrations
 
             modelBuilder.Entity("Volo.Abp.Identity.IdentityUserToken", b =>
                 {
-                    b.Property<string>("Id")
+                    b.Property<Guid>("Id")
                         .ValueGeneratedOnAdd();
 
                     b.Property<string>("LoginProvider");
 
                     b.Property<string>("Name");
 
-                    b.Property<string>("UserId")
-                        .IsRequired();
+                    b.Property<Guid>("UserId");
 
                     b.Property<string>("Value");
 
diff --git a/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EfCoreIdentityUserRepository.cs b/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EfCoreIdentityUserRepository.cs
index 2fad6cd8c2..c458b87cac 100644
--- a/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EfCoreIdentityUserRepository.cs
+++ b/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EfCoreIdentityUserRepository.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Threading;
 using System.Linq;
 using System.Security.Claims;
@@ -22,7 +23,7 @@ namespace Volo.Abp.Identity
             return DbSet.FirstOrDefaultAsync(u => u.NormalizedUserName == normalizedUserName, cancellationToken);
         }
 
-        public Task<List<string>> GetRoleNamesAsync(string userId)
+        public Task<List<string>> GetRoleNamesAsync(Guid userId)
         {
             var query = from userRole in DbContext.UserRoles
                         join role in DbContext.Roles on userRole.RoleId equals role.Id
diff --git a/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/IdentityDbContext.cs b/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/IdentityDbContext.cs
index a5265a9ce1..df804cdde2 100644
--- a/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/IdentityDbContext.cs
+++ b/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/IdentityDbContext.cs
@@ -69,7 +69,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore
             {
                 b.ToTable("IdentityUsers");
 
-                b.Property(u => u.ConcurrencyStamp).IsConcurrencyToken();
+                b.Property(u => u.ConcurrencyStamp).IsConcurrencyToken(); //TODO: Do automatically?
                 b.Property(u => u.UserName).HasMaxLength(256);
                 b.Property(u => u.NormalizedUserName).HasMaxLength(256);
                 b.Property(u => u.Email).HasMaxLength(256);
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IIdentityUserRepository.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IIdentityUserRepository.cs
index 347b02c202..0342e800cf 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IIdentityUserRepository.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IIdentityUserRepository.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Security.Claims;
 using System.Threading;
 using System.Threading.Tasks;
@@ -11,7 +12,7 @@ namespace Volo.Abp.Identity
     {
         Task<IdentityUser> FindByNormalizedUserNameAsync([NotNull] string normalizedUserName, CancellationToken cancellationToken);
 
-        Task<List<string>> GetRoleNamesAsync([NotNull] string userId);
+        Task<List<string>> GetRoleNamesAsync(Guid userId);
 
         Task<IdentityUser> FindByLoginAsync([NotNull] string loginProvider, [NotNull] string providerKey, CancellationToken cancellationToken);
 
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityRoleClaim.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityRoleClaim.cs
index d62d303535..e831db3642 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityRoleClaim.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityRoleClaim.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Security.Claims;
 using JetBrains.Annotations;
 using Volo.Abp.Domain.Entities;
@@ -12,7 +13,7 @@ namespace Volo.Abp.Identity
         /// <summary>
         /// Gets or sets the of the primary key of the role associated with this claim.
         /// </summary>
-        public virtual string RoleId { get; protected set; }
+        public virtual Guid RoleId { get; protected set; }
 
         /// <summary>
         /// Gets or sets the claim type for this claim.
@@ -29,9 +30,8 @@ namespace Volo.Abp.Identity
             
         }
 
-        public IdentityRoleClaim([NotNull] string roleId, [NotNull] Claim claim)
+        public IdentityRoleClaim(Guid roleId, [NotNull] Claim claim)
         {
-            Check.NotNull(roleId, nameof(roleId));
             Check.NotNull(claim, nameof(claim));
 
             RoleId = roleId;
@@ -39,7 +39,7 @@ namespace Volo.Abp.Identity
             ClaimValue = claim.Value;
         }
 
-        public IdentityRoleClaim([NotNull] string roleId, [NotNull] string claimType, string claimValue)
+        public IdentityRoleClaim(Guid roleId, [NotNull] string claimType, string claimValue)
         {
             Check.NotNull(roleId, nameof(roleId));
             Check.NotNull(claimType, nameof(claimType));
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUser.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUser.cs
index e22ab4829c..b5970093af 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUser.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUser.cs
@@ -128,7 +128,7 @@ namespace Volo.Abp.Identity
             UserName = userName;
         }
 
-        public void AddRole([NotNull] string roleId)
+        public void AddRole([NotNull] Guid roleId)
         {
             Check.NotNull(roleId, nameof(roleId));
 
@@ -140,7 +140,7 @@ namespace Volo.Abp.Identity
             Roles.Add(new IdentityUserRole(Id, roleId));
         }
 
-        public void RemoveRole([NotNull] string roleId)
+        public void RemoveRole(Guid roleId)
         {
             Check.NotNull(roleId, nameof(roleId));
 
@@ -152,7 +152,7 @@ namespace Volo.Abp.Identity
             Roles.Add(new IdentityUserRole(Id, roleId));
         }
 
-        public bool IsInRole([NotNull] string roleId)
+        public bool IsInRole(Guid roleId)
         {
             Check.NotNull(roleId, nameof(roleId));
 
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserClaim.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserClaim.cs
index 9eb97a4eeb..6dd7a56020 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserClaim.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserClaim.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Security.Claims;
 using JetBrains.Annotations;
 using Volo.Abp.Domain.Entities;
@@ -12,7 +13,7 @@ namespace Volo.Abp.Identity
         /// <summary>
         /// Gets or sets the primary key of the user associated with this claim.
         /// </summary>
-        public virtual string UserId { get; protected set; }
+        public virtual Guid UserId { get; protected set; }
 
         /// <summary>
         /// Gets or sets the claim type for this claim.
@@ -29,9 +30,8 @@ namespace Volo.Abp.Identity
             
         }
 
-        public IdentityUserClaim([NotNull] string userId, [NotNull] Claim claim)
+        public IdentityUserClaim(Guid userId, [NotNull] Claim claim)
         {
-            Check.NotNull(userId, nameof(userId));
             Check.NotNull(claim, nameof(claim));
 
             UserId = userId;
@@ -39,9 +39,8 @@ namespace Volo.Abp.Identity
             ClaimValue = claim.Value;
         }
 
-        public IdentityUserClaim([NotNull] string userId, [NotNull] string claimType, string claimValue)
+        public IdentityUserClaim(Guid userId, [NotNull] string claimType, string claimValue)
         {
-            Check.NotNull(userId, nameof(userId));
             Check.NotNull(claimType, nameof(claimType));
 
             UserId = userId;
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserLogin.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserLogin.cs
index defec8c4cc..eb32b92c9b 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserLogin.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserLogin.cs
@@ -1,3 +1,4 @@
+using System;
 using JetBrains.Annotations;
 using Microsoft.AspNetCore.Identity;
 using Volo.Abp.Domain.Entities;
@@ -14,7 +15,7 @@ namespace Volo.Abp.Identity
         /// <summary>
         /// Gets or sets the of the primary key of the user associated with this login.
         /// </summary>
-        public virtual string UserId { get; protected set; }
+        public virtual Guid UserId { get; protected set; }
 
         /// <summary>
         /// Gets or sets the login provider for the login (e.g. facebook, google)
@@ -36,9 +37,8 @@ namespace Volo.Abp.Identity
             
         }
 
-        public IdentityUserLogin([NotNull] string userId, [NotNull] string loginProvider, [NotNull] string providerKey, string providerDisplayName)
+        public IdentityUserLogin(Guid userId, [NotNull] string loginProvider, [NotNull] string providerKey, string providerDisplayName)
         {
-            Check.NotNull(userId, nameof(userId));
             Check.NotNull(loginProvider, nameof(loginProvider));
             Check.NotNull(providerKey, nameof(providerKey));
 
@@ -48,9 +48,8 @@ namespace Volo.Abp.Identity
             ProviderDisplayName = providerDisplayName;
         }
 
-        public IdentityUserLogin(string userId, UserLoginInfo login)
+        public IdentityUserLogin(Guid userId, UserLoginInfo login)
         {
-            Check.NotNull(userId, nameof(userId));
             Check.NotNull(login, nameof(login));
 
             UserId = userId;
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserRole.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserRole.cs
index 8b332e82a4..8f8a591bc1 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserRole.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserRole.cs
@@ -1,4 +1,4 @@
-using JetBrains.Annotations;
+using System;
 using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Identity
@@ -11,23 +11,20 @@ namespace Volo.Abp.Identity
         /// <summary>
         /// Gets or sets the primary key of the user that is linked to a role.
         /// </summary>
-        public virtual string UserId { get; protected set; }
+        public virtual Guid UserId { get; protected set; }
 
         /// <summary>
         /// Gets or sets the primary key of the role that is linked to the user.
         /// </summary>
-        public virtual string RoleId { get; protected set; }
+        public virtual Guid RoleId { get; protected set; }
 
         protected IdentityUserRole()
         {
             
         }
 
-        public IdentityUserRole([NotNull] string userId, [NotNull] string roleId)
+        public IdentityUserRole(Guid userId, Guid roleId)
         {
-            Check.NotNull(userId, nameof(userId));
-            Check.NotNull(roleId, nameof(roleId));
-
             UserId = userId;
             RoleId = roleId;
         }
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserToken.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserToken.cs
index 4da14a23d6..fd750d851b 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserToken.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/IdentityUserToken.cs
@@ -1,3 +1,4 @@
+using System;
 using JetBrains.Annotations;
 using Volo.Abp.Domain.Entities;
 
@@ -11,7 +12,7 @@ namespace Volo.Abp.Identity
         /// <summary>
         /// Gets or sets the primary key of the user that the token belongs to.
         /// </summary>
-        public virtual string UserId { get; protected set; }
+        public virtual Guid UserId { get; protected set; }
 
         /// <summary>
         /// Gets or sets the LoginProvider this token is from.
@@ -33,7 +34,7 @@ namespace Volo.Abp.Identity
             
         }
 
-        public IdentityUserToken([NotNull] string userId, [NotNull] string loginProvider, [NotNull] string name, string value) //TODO: Can value be null?
+        public IdentityUserToken(Guid userId, [NotNull] string loginProvider, [NotNull] string name, string value) //TODO: Can value be null?
         {
             Check.NotNull(userId, nameof(userId));
             Check.NotNull(loginProvider, nameof(loginProvider));
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/RoleStore.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/RoleStore.cs
index e1606b53b1..05b6ec5261 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/RoleStore.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/RoleStore.cs
@@ -77,7 +77,7 @@ namespace Volo.Abp.Identity
 
             Check.NotNull(role, nameof(role));
 
-            await _roleRepository.InsertAsync(role);
+            await _roleRepository.InsertAsync(role, cancellationToken: cancellationToken);
             await SaveChanges(cancellationToken);
 
             return IdentityResult.Success;
@@ -96,7 +96,7 @@ namespace Volo.Abp.Identity
 
             Check.NotNull(role, nameof(role));
 
-            await _roleRepository.UpdateAsync(role);
+            await _roleRepository.UpdateAsync(role, cancellationToken);
 
             try
             {
@@ -126,7 +126,7 @@ namespace Volo.Abp.Identity
 
             try
             {
-                await _roleRepository.DeleteAsync(role);
+                await _roleRepository.DeleteAsync(role, cancellationToken);
                 await SaveChanges(cancellationToken);
             }
             catch (AbpDbConcurrencyException ex)
@@ -151,7 +151,7 @@ namespace Volo.Abp.Identity
 
             Check.NotNull(role, nameof(role));
 
-            return Task.FromResult(role.Id);
+            return Task.FromResult(role.Id.ToString());
         }
 
         /// <summary>
@@ -194,15 +194,12 @@ namespace Volo.Abp.Identity
         /// <param name="id">The role ID to look for.</param>
         /// <param name="cancellationToken">The <see cref="CancellationToken"/> used to propagate notifications that the operation should be canceled.</param>
         /// <returns>A <see cref="Task{TResult}"/> that result of the look up.</returns>
-        public virtual Task<IdentityRole> FindByIdAsync([NotNull] string id, CancellationToken cancellationToken = default(CancellationToken))
+        public virtual Task<IdentityRole> FindByIdAsync(string id, CancellationToken cancellationToken = default(CancellationToken))
         {
             cancellationToken.ThrowIfCancellationRequested();
             ThrowIfDisposed();
 
-            Check.NotNull(id, nameof(id));
-
-            //TODO: Add cancellationToken to Repository.FindAsync method as overload
-            return _roleRepository.FindAsync(id);
+            return _roleRepository.FindAsync(Guid.Parse(id), cancellationToken);
         }
 
         /// <summary>
diff --git a/src/Volo.Abp.Identity/Volo/Abp/Identity/UserStore.cs b/src/Volo.Abp.Identity/Volo/Abp/Identity/UserStore.cs
index e69da199d4..b798ca7af5 100644
--- a/src/Volo.Abp.Identity/Volo/Abp/Identity/UserStore.cs
+++ b/src/Volo.Abp.Identity/Volo/Abp/Identity/UserStore.cs
@@ -87,7 +87,7 @@ namespace Volo.Abp.Identity
 
             Check.NotNull(user, nameof(user));
 
-            return Task.FromResult(user.Id);
+            return Task.FromResult(user.Id.ToString());
         }
 
         /// <summary>
@@ -241,15 +241,12 @@ namespace Volo.Abp.Identity
         /// <returns>
         /// The <see cref="Task"/> that represents the asynchronous operation, containing the user matching the specified <paramref name="userId"/> if it exists.
         /// </returns>
-        public virtual Task<IdentityUser> FindByIdAsync([NotNull] string userId, CancellationToken cancellationToken = default(CancellationToken))
+        public virtual Task<IdentityUser> FindByIdAsync(string userId, CancellationToken cancellationToken = default(CancellationToken))
         {
             cancellationToken.ThrowIfCancellationRequested();
             ThrowIfDisposed();
 
-            Check.NotNull(userId, nameof(userId));
-
-            //TODO: Add cancellationToken to Repository.FindAsync method as overload
-            return _userRepository.FindAsync(userId);
+            return _userRepository.FindAsync(Guid.Parse(userId), cancellationToken);
         }
 
         /// <summary>
diff --git a/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/IMongoDbRepository.cs b/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/IMongoDbRepository.cs
index 8b427ad263..82ffb23f6b 100644
--- a/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/IMongoDbRepository.cs
+++ b/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/IMongoDbRepository.cs
@@ -1,10 +1,11 @@
-using MongoDB.Driver;
+using System;
+using MongoDB.Driver;
 using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Domain.Repositories.MongoDB
 {
-    public interface IMongoDbRepository<TEntity> : IMongoDbRepository<TEntity, string>, IQueryableRepository<TEntity>
-        where TEntity : class, IEntity<string>
+    public interface IMongoDbRepository<TEntity> : IMongoDbRepository<TEntity, Guid>, IQueryableRepository<TEntity>
+        where TEntity : class, IEntity<Guid>
     {
         
     }
diff --git a/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/MongoDbRepository.cs b/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/MongoDbRepository.cs
index 73e42bffce..6c183ca5a7 100644
--- a/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/MongoDbRepository.cs
+++ b/src/Volo.Abp.MongoDB/Volo/Abp/Domain/Repositories/MongoDB/MongoDbRepository.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using MongoDB.Driver;
 using Volo.Abp.Domain.Entities;
@@ -5,9 +6,9 @@ using Volo.Abp.MongoDB;
 
 namespace Volo.Abp.Domain.Repositories.MongoDB
 {
-    public class MongoDbRepository<TMongoDbContext, TEntity> : MongoDbRepository<TMongoDbContext, TEntity, string>, IMongoDbRepository<TEntity>
+    public class MongoDbRepository<TMongoDbContext, TEntity> : MongoDbRepository<TMongoDbContext, TEntity, Guid>, IMongoDbRepository<TEntity>
         where TMongoDbContext : AbpMongoDbContext
-        where TEntity : class, IEntity<string>
+        where TEntity : class, IEntity<Guid>
     {
         public MongoDbRepository(IMongoDatabaseProvider<TMongoDbContext> databaseProvider)
             : base(databaseProvider)
diff --git a/src/Volo.Abp/Microsoft/Extensions/DependencyInjection/ServiceCollectionRepositoryExtensions.cs b/src/Volo.Abp/Microsoft/Extensions/DependencyInjection/ServiceCollectionRepositoryExtensions.cs
index 9b4c5a1e15..12b0a3dbba 100644
--- a/src/Volo.Abp/Microsoft/Extensions/DependencyInjection/ServiceCollectionRepositoryExtensions.cs
+++ b/src/Volo.Abp/Microsoft/Extensions/DependencyInjection/ServiceCollectionRepositoryExtensions.cs
@@ -62,7 +62,7 @@ namespace Microsoft.Extensions.DependencyInjection
 
         private static bool BothSupportsDefaultPrimaryKey(Type entityType, Type repositoryImplementationType)
         {
-            return typeof(IEntity<string>).GetTypeInfo().IsAssignableFrom(entityType) &&
+            return typeof(IEntity<Guid>).GetTypeInfo().IsAssignableFrom(entityType) &&
                    ReflectionHelper.IsAssignableToGenericType(repositoryImplementationType, typeof(IRepository<>));
         }
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Entities/AggregateRoot.cs b/src/Volo.Abp/Volo/Abp/Domain/Entities/AggregateRoot.cs
index 30660acbba..1b432ca950 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Entities/AggregateRoot.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Entities/AggregateRoot.cs
@@ -1,6 +1,8 @@
-namespace Volo.Abp.Domain.Entities
+using System;
+
+namespace Volo.Abp.Domain.Entities
 {
-    public class AggregateRoot : AggregateRoot<string>, IAggregateRoot
+    public class AggregateRoot : AggregateRoot<Guid>, IAggregateRoot
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Entities/DefaultIdGenerator.cs b/src/Volo.Abp/Volo/Abp/Domain/Entities/DefaultIdGenerator.cs
index bb075812c1..6c91ca72fc 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Entities/DefaultIdGenerator.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Entities/DefaultIdGenerator.cs
@@ -4,6 +4,7 @@ using Volo.DependencyInjection;
 
 namespace Volo.Abp.Domain.Entities
 {
+    //TODO: No need! Directly use Guid Generator!
     public class DefaultIdGenerator : IIdGenerator, ITransientDependency
     {
         private readonly IGuidGenerator _guidGenerator;
@@ -15,7 +16,7 @@ namespace Volo.Abp.Domain.Entities
 
         public string GenerateStringId()
         {
-            return GenerateGuid().ToString("D");
+            return GenerateGuid().ToString();
         }
 
         public Guid GenerateGuid()
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Entities/Entity.cs b/src/Volo.Abp/Volo/Abp/Domain/Entities/Entity.cs
index 15c0971e46..302e673c11 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Entities/Entity.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Entities/Entity.cs
@@ -7,7 +7,7 @@ namespace Volo.Abp.Domain.Entities
     /// <summary>
     /// A shortcut of <see cref="Entity{TPrimaryKey}"/> for default primary key type (<see cref="string"/>).
     /// </summary>
-    public abstract class Entity : Entity<string>, IEntity
+    public abstract class Entity : Entity<Guid>, IEntity
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Entities/IAggregateRoot.cs b/src/Volo.Abp/Volo/Abp/Domain/Entities/IAggregateRoot.cs
index 621004c93e..9ef287eb68 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Entities/IAggregateRoot.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Entities/IAggregateRoot.cs
@@ -1,6 +1,8 @@
-namespace Volo.Abp.Domain.Entities
+using System;
+
+namespace Volo.Abp.Domain.Entities
 {
-    public interface IAggregateRoot : IAggregateRoot<string>, IEntity
+    public interface IAggregateRoot : IAggregateRoot<Guid>, IEntity
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Entities/IEntity.cs b/src/Volo.Abp/Volo/Abp/Domain/Entities/IEntity.cs
index fd5f75287e..2d48ee20e7 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Entities/IEntity.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Entities/IEntity.cs
@@ -1,9 +1,11 @@
-namespace Volo.Abp.Domain.Entities
+using System;
+
+namespace Volo.Abp.Domain.Entities
 {
     /// <summary>
     /// A shortcut of <see cref="IEntity{TPrimaryKey}"/> for default primary key type (<see cref="string"/>).
     /// </summary>
-    public interface IEntity : IEntity<string>
+    public interface IEntity : IEntity<Guid>
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Repositories/IQueryableRepository.cs b/src/Volo.Abp/Volo/Abp/Domain/Repositories/IQueryableRepository.cs
index ad0a56f8c6..48217e2773 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Repositories/IQueryableRepository.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Repositories/IQueryableRepository.cs
@@ -8,8 +8,8 @@ using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Domain.Repositories
 {
-    public interface IQueryableRepository<TEntity> : IQueryableRepository<TEntity, string>, IRepository<TEntity>
-        where TEntity : class, IEntity<string>
+    public interface IQueryableRepository<TEntity> : IQueryableRepository<TEntity, Guid>, IRepository<TEntity>
+        where TEntity : class, IEntity<Guid>
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Repositories/IRepository.cs b/src/Volo.Abp/Volo/Abp/Domain/Repositories/IRepository.cs
index 8dbfa715b2..c086c3223d 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Repositories/IRepository.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Repositories/IRepository.cs
@@ -1,4 +1,5 @@
-using System.Threading;
+using System;
+using System.Threading;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
 using Volo.Abp.Domain.Entities;
@@ -11,8 +12,8 @@ namespace Volo.Abp.Domain.Repositories
 
     }
 
-    public interface IRepository<TEntity> : IRepository<TEntity, string>
-        where TEntity : class, IEntity<string>
+    public interface IRepository<TEntity> : IRepository<TEntity, Guid>
+        where TEntity : class, IEntity<Guid>
     {
         
     }
@@ -66,6 +67,7 @@ namespace Volo.Abp.Domain.Repositories
         [NotNull]
         TEntity Insert([NotNull] TEntity entity, bool autoSave = false);
 
+        //TODO: Consider to add a new overload that takes cancellationToken as second argument?
         /// <summary>
         /// Inserts a new entity.
         /// </summary>
@@ -76,7 +78,7 @@ namespace Volo.Abp.Domain.Repositories
         /// <param name="cancellationToken">A <see cref="T:System.Threading.CancellationToken" /> to observe while waiting for the task to complete.</param>
         /// <param name="entity">Inserted entity</param>
         [NotNull]
-        Task<TEntity> InsertAsync([NotNull] TEntity entity, bool autoSave = true, CancellationToken cancellationToken = default(CancellationToken));
+        Task<TEntity> InsertAsync([NotNull] TEntity entity, bool autoSave = false, CancellationToken cancellationToken = default(CancellationToken));
 
         /// <summary>
         /// Updates an existing entity.
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Repositories/QueryableRepositoryBase.cs b/src/Volo.Abp/Volo/Abp/Domain/Repositories/QueryableRepositoryBase.cs
index 1833e87418..7e9866179f 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Repositories/QueryableRepositoryBase.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Repositories/QueryableRepositoryBase.cs
@@ -9,8 +9,8 @@ using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Domain.Repositories
 {
-    public abstract class QueryableRepositoryBase<TEntity> : QueryableRepositoryBase<TEntity, string>, IQueryableRepository<TEntity>
-        where TEntity : class, IEntity<string>
+    public abstract class QueryableRepositoryBase<TEntity> : QueryableRepositoryBase<TEntity, Guid>, IQueryableRepository<TEntity>
+        where TEntity : class, IEntity<Guid>
     {
         
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryBase.cs b/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryBase.cs
index 290d74f60b..b80d7d14b9 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryBase.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryBase.cs
@@ -6,8 +6,8 @@ using Volo.Abp.Domain.Entities;
 
 namespace Volo.Abp.Domain.Repositories
 {
-    public abstract class RepositoryBase<TEntity> : RepositoryBase<TEntity, string>, IRepository<TEntity>
-        where TEntity : class, IEntity<string>
+    public abstract class RepositoryBase<TEntity> : RepositoryBase<TEntity, Guid>, IRepository<TEntity>
+        where TEntity : class, IEntity<Guid>
     {
 
     }
diff --git a/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs b/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
index 6426f892bb..e769e36f3c 100644
--- a/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
+++ b/src/Volo.Abp/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
@@ -45,7 +45,7 @@ namespace Volo.Abp.Domain.Repositories
         protected void RegisterDefaultRepository(IServiceCollection services, Type dbContextType, Type entityType)
         {
             var primaryKeyType = EntityHelper.GetPrimaryKeyType(entityType);
-            var isDefaultPrimaryKey = primaryKeyType == typeof(string);
+            var isDefaultPrimaryKey = primaryKeyType == typeof(Guid);
 
             Type repositoryImplementationType;
             if (Options.SpecifiedDefaultRepositoryTypes)
diff --git a/test/Volo.Abp.Identity.Tests/Volo/Abp/Identity/Initialize_Tests.cs b/test/Volo.Abp.Identity.Tests/Volo/Abp/Identity/Initialize_Tests.cs
index e7f3b28ead..ac8b510eaa 100644
--- a/test/Volo.Abp.Identity.Tests/Volo/Abp/Identity/Initialize_Tests.cs
+++ b/test/Volo.Abp.Identity.Tests/Volo/Abp/Identity/Initialize_Tests.cs
@@ -1,4 +1,5 @@
-using Microsoft.Extensions.DependencyInjection;
+using System;
+using Microsoft.Extensions.DependencyInjection;
 using Shouldly;
 using Volo.Abp.Domain.Repositories;
 using Volo.Abp.TestBase;
@@ -26,10 +27,10 @@ namespace Volo.Abp.Identity
         {
             (ServiceProvider.GetRequiredService<IIdentityUserRepository>() is EfCoreIdentityUserRepository).ShouldBeTrue();
 
-            (ServiceProvider.GetRequiredService<IRepository<IdentityUser, string>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
+            (ServiceProvider.GetRequiredService<IRepository<IdentityUser, Guid>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
             (ServiceProvider.GetRequiredService<IRepository<IdentityUser>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
 
-            (ServiceProvider.GetRequiredService<IQueryableRepository<IdentityUser, string>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
+            (ServiceProvider.GetRequiredService<IQueryableRepository<IdentityUser, Guid>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
             (ServiceProvider.GetRequiredService<IQueryableRepository<IdentityUser>>() is EfCoreIdentityUserRepository).ShouldBeTrue();
         }
     }
diff --git a/test/Volo.Abp.Tests/Volo/Abp/Domain/Repositories/RepositoryRegistration_Tests.cs b/test/Volo.Abp.Tests/Volo/Abp/Domain/Repositories/RepositoryRegistration_Tests.cs
index 1dfa092649..59c444eed7 100644
--- a/test/Volo.Abp.Tests/Volo/Abp/Domain/Repositories/RepositoryRegistration_Tests.cs
+++ b/test/Volo.Abp.Tests/Volo/Abp/Domain/Repositories/RepositoryRegistration_Tests.cs
@@ -26,7 +26,7 @@ namespace Volo.Abp.Domain.Repositories
             //Assert
 
             services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
-            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, string>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
+            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, Guid>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
             services.ShouldNotContainService(typeof(IRepository<MyTestEntityWithCustomPk, int>));
         }
 
@@ -47,7 +47,7 @@ namespace Volo.Abp.Domain.Repositories
             //Assert
 
             services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
-            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, string>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
+            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, Guid>), typeof(MyTestDefaultRepository<MyTestAggregateRootWithDefaultPk>));
             services.ShouldContainTransient(typeof(IRepository<MyTestEntityWithCustomPk, int>), typeof(MyTestDefaultRepository<MyTestEntityWithCustomPk, int>));
         }
 
@@ -70,7 +70,7 @@ namespace Volo.Abp.Domain.Repositories
             //Assert
 
             services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk>), typeof(MyTestAggregateRootWithDefaultPkCustomRepository));
-            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, string>), typeof(MyTestAggregateRootWithDefaultPkCustomRepository));
+            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, Guid>), typeof(MyTestAggregateRootWithDefaultPkCustomRepository));
             services.ShouldContainTransient(typeof(IRepository<MyTestEntityWithCustomPk, int>), typeof(MyTestDefaultRepository<MyTestEntityWithCustomPk, int>));
         }
 
@@ -93,7 +93,7 @@ namespace Volo.Abp.Domain.Repositories
             //Assert
 
             services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk>), typeof(MyTestCustomBaseRepository<MyTestAggregateRootWithDefaultPk>));
-            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, string>), typeof(MyTestCustomBaseRepository<MyTestAggregateRootWithDefaultPk>));
+            services.ShouldContainTransient(typeof(IRepository<MyTestAggregateRootWithDefaultPk, Guid>), typeof(MyTestCustomBaseRepository<MyTestAggregateRootWithDefaultPk>));
             services.ShouldContainTransient(typeof(IRepository<MyTestEntityWithCustomPk, int>), typeof(MyTestCustomBaseRepository<MyTestEntityWithCustomPk, int>));
         }
 
@@ -136,8 +136,8 @@ namespace Volo.Abp.Domain.Repositories
 
         }
 
-        public class MyTestDefaultRepository<TEntity> : MyTestDefaultRepository<TEntity, string>, IRepository<TEntity>
-            where TEntity : class, IEntity<string>
+        public class MyTestDefaultRepository<TEntity> : MyTestDefaultRepository<TEntity, Guid>, IRepository<TEntity>
+            where TEntity : class, IEntity<Guid>
         {
             
         }
@@ -171,8 +171,8 @@ namespace Volo.Abp.Domain.Repositories
 
         }
 
-        public class MyTestCustomBaseRepository<TEntity> : MyTestCustomBaseRepository<TEntity, string>, IRepository<TEntity>
-            where TEntity : class, IEntity<string>
+        public class MyTestCustomBaseRepository<TEntity> : MyTestCustomBaseRepository<TEntity, Guid>, IRepository<TEntity>
+            where TEntity : class, IEntity<Guid>
         {
 
         }