diff --git a/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityRoleRepository.cs b/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityRoleRepository.cs
index 282b52a79d..c101bdddb5 100644
--- a/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityRoleRepository.cs
+++ b/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityRoleRepository.cs
@@ -38,7 +38,7 @@ namespace Volo.Abp.Identity.EntityFrameworkCore
         {
             return await DbSet
                 .IncludeDetails(includeDetails)
-                .WhereIf(filter != null,
+                .WhereIf(!filter.IsNullOrWhiteSpace(),
                         x => x.Name.Contains(filter) ||
                         x.NormalizedName.Contains(filter))
                 .OrderBy(sorting ?? nameof(IdentityRole.Name))
diff --git a/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityRoleRepository.cs b/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityRoleRepository.cs
index 3c4042c95d..68fda4f840 100644
--- a/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityRoleRepository.cs
+++ b/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityRoleRepository.cs
@@ -36,7 +36,7 @@ namespace Volo.Abp.Identity.MongoDB
             CancellationToken cancellationToken = default)
         {
             return await GetMongoQueryable()
-                .WhereIf(filter != null,
+                .WhereIf(!filter.IsNullOrWhiteSpace(),
                         x => x.Name.Contains(filter) ||
                         x.NormalizedName.Contains(filter))
                 .OrderBy(sorting ?? nameof(IdentityRole.Name))
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/ApiResources/ApiResourceRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/ApiResources/ApiResourceRepository.cs
index f40962ccc8..d4fc77ede2 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/ApiResources/ApiResourceRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/ApiResources/ApiResourceRepository.cs
@@ -50,7 +50,7 @@ namespace Volo.Abp.IdentityServer.ApiResources
         {
             return await DbSet
                 .IncludeDetails(includeDetails)
-                .WhereIf(filter != null, x => x.Name.Contains(filter) ||
+                .WhereIf(!filter.IsNullOrWhiteSpace(), x => x.Name.Contains(filter) ||
                          x.Description.Contains(filter) ||
                          x.DisplayName.Contains(filter))
                 .OrderBy(sorting ?? "name desc")
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/Clients/ClientRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/Clients/ClientRepository.cs
index 44b65e6147..5b350d0365 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/Clients/ClientRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/Clients/ClientRepository.cs
@@ -34,7 +34,7 @@ namespace Volo.Abp.IdentityServer.Clients
         {
             return await DbSet
                 .IncludeDetails(includeDetails)
-                .WhereIf(filter != null, x => x.ClientId.Contains(filter))
+                .WhereIf(!filter.IsNullOrWhiteSpace(), x => x.ClientId.Contains(filter))
                 .OrderBy(sorting ?? nameof(Client.ClientName) + " desc")
                 .PageBy(skipCount, maxResultCount)
                 .ToListAsync(GetCancellationToken(cancellationToken));
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/IdentityResources/IdentityResourceRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/IdentityResources/IdentityResourceRepository.cs
index c39a6633f2..faed5fb67a 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/IdentityResources/IdentityResourceRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.EntityFrameworkCore/Volo/Abp/IdentityServer/IdentityResources/IdentityResourceRepository.cs
@@ -41,7 +41,7 @@ namespace Volo.Abp.IdentityServer.IdentityResources
         {
             return await DbSet
                 .IncludeDetails(includeDetails)
-                .WhereIf(filter != null, x => x.Name.Contains(filter) ||
+                .WhereIf(!filter.IsNullOrWhiteSpace(), x => x.Name.Contains(filter) ||
                          x.Description.Contains(filter) ||
                          x.DisplayName.Contains(filter))
                 .OrderBy(sorting ?? "name desc")
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoApiResourceRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoApiResourceRepository.cs
index e08c3f1a28..d2c89f193c 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoApiResourceRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoApiResourceRepository.cs
@@ -37,7 +37,7 @@ namespace Volo.Abp.IdentityServer.MongoDB
             CancellationToken cancellationToken = default)
         {
             return await GetMongoQueryable()
-                .WhereIf(filter != null,
+                .WhereIf(!filter.IsNullOrWhiteSpace(),
                          x => x.Name.Contains(filter) ||
                          x.Description.Contains(filter) ||
                          x.DisplayName.Contains(filter))
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoClientRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoClientRepository.cs
index 0459e12b21..5855c42513 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoClientRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoClientRepository.cs
@@ -38,7 +38,7 @@ namespace Volo.Abp.IdentityServer.MongoDB
             CancellationToken cancellationToken = default)
         {
             return await GetMongoQueryable()
-                .WhereIf(filter != null, x=>x.ClientId.Contains(filter))
+                .WhereIf(!filter.IsNullOrWhiteSpace(), x=>x.ClientId.Contains(filter))
                 .OrderBy(sorting ?? nameof(Client.ClientName))
                 .As<IMongoQueryable<Client>>()
                 .PageBy<Client, IMongoQueryable<Client>>(skipCount, maxResultCount)
diff --git a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoIdentityResourceRepository.cs b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoIdentityResourceRepository.cs
index 3c0ef4a135..e166ee9ec5 100644
--- a/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoIdentityResourceRepository.cs
+++ b/modules/identityserver/src/Volo.Abp.IdentityServer.MongoDB/Volo/Abp/IdentityServer/MongoDB/MongoIdentityResourceRepository.cs
@@ -18,10 +18,10 @@ namespace Volo.Abp.IdentityServer.MongoDB
         {
         }
 
-        public virtual async Task<List<IdentityResource>> GetListAsync(string sorting, int skipCount, int maxResultCount,string filter, bool includeDetails = false, CancellationToken cancellationToken = default)
+        public virtual async Task<List<IdentityResource>> GetListAsync(string sorting, int skipCount, int maxResultCount, string filter, bool includeDetails = false, CancellationToken cancellationToken = default)
         {
             return await GetMongoQueryable()
-                .WhereIf(filter != null, x => x.Name.Contains(filter) ||
+                .WhereIf(!filter.IsNullOrWhiteSpace(), x => x.Name.Contains(filter) ||
                          x.Description.Contains(filter) ||
                          x.DisplayName.Contains(filter))
                 .OrderBy(sorting ?? nameof(IdentityResource.Name))