Added alternative WhereIf and PageIf for extended queryables.

src/Volo.Abp.Core/System/Linq/AbpQueryableExtensions.cs

@@ -19,6 +19,17 @@ namespace System.Linq
             return query.Skip(skipCount).Take(maxResultCount);
         }
 
+        /// <summary>
+        /// Used for paging. Can be used as an alternative to Skip(...).Take(...) chaining.
+        /// </summary>
+        public static TQueryable PageBy<T, TQueryable>([NotNull] this TQueryable query, int skipCount, int maxResultCount)
+            where TQueryable : IQueryable<T>
+        {
+            Check.NotNull(query, nameof(query));
+
+            return (TQueryable) query.Skip(skipCount).Take(maxResultCount);
+        }
+
         /// <summary>
         /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
         /// </summary>
@@ -35,6 +46,23 @@ namespace System.Linq
                 : query;
         }
 
+        /// <summary>
+        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
+        /// </summary>
+        /// <param name="query">Queryable to apply filtering</param>
+        /// <param name="condition">A boolean value</param>
+        /// <param name="predicate">Predicate to filter the query</param>
+        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
+        public static TQueryable WhereIf<T, TQueryable>([NotNull] this TQueryable query, bool condition, Expression<Func<T, bool>> predicate)
+            where TQueryable : IQueryable<T>
+        {
+            Check.NotNull(query, nameof(query));
+
+            return condition
+                ? (TQueryable) query.Where(predicate)
+                : query;
+        }
+
         /// <summary>
         /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
         /// </summary>
@@ -50,5 +78,22 @@ namespace System.Linq
                 ? query.Where(predicate)
                 : query;
         }
+
+        /// <summary>
+        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
+        /// </summary>
+        /// <param name="query">Queryable to apply filtering</param>
+        /// <param name="condition">A boolean value</param>
+        /// <param name="predicate">Predicate to filter the query</param>
+        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
+        public static TQueryable WhereIf<T, TQueryable>([NotNull] this TQueryable query, bool condition, Expression<Func<T, int, bool>> predicate)
+            where TQueryable : IQueryable<T>
+        {
+            Check.NotNull(query, nameof(query));
+
+            return condition
+                ? (TQueryable) query.Where(predicate)
+                : query;
+        }
     }
 }