Update PagedResult logic (#349)

* Add int? rowCount to PageResult

* fix

Author: StefH

src/System.Linq.Dynamic.Core/DynamicQueryableExtensions.cs

@@ -1360,18 +1360,20 @@ public static IQueryable<TSource> Page<TSource>([NotNull] this IQueryable<TSourc
         /// <param name="source">The IQueryable to return elements from.</param>
         /// <param name="page">The page to return.</param>
         /// <param name="pageSize">The number of elements per page.</param>
+        /// <param name="rowCount">If this optional parameter has been defined, this value is used as the RowCount instead of executing a Linq `Count()`.</param>
         /// <returns>PagedResult</returns>
-        public static PagedResult PageResult([NotNull] this IQueryable source, int page, int pageSize)
+        public static PagedResult PageResult([NotNull] this IQueryable source, int page, int pageSize, int? rowCount = null)
         {
             Check.NotNull(source, nameof(source));
             Check.Condition(page, p => p > 0, nameof(page));
             Check.Condition(pageSize, ps => ps > 0, nameof(pageSize));
+            Check.Condition(rowCount, rc => rc == null || rc >= 0, nameof(rowCount));
 
             var result = new PagedResult
             {
                 CurrentPage = page,
                 PageSize = pageSize,
-                RowCount = source.Count()
+                RowCount = rowCount ?? source.Count()
             };
 
             result.PageCount = (int)Math.Ceiling((double)result.RowCount / pageSize);
@@ -1387,18 +1389,20 @@ public static PagedResult PageResult([NotNull] this IQueryable source, int page,
         /// <param name="source">The IQueryable to return elements from.</param>
         /// <param name="page">The page to return.</param>
         /// <param name="pageSize">The number of elements per page.</param>
+        /// <param name="rowCount">If this optional parameter has been defined, this value is used as the RowCount instead of executing a Linq `Count()`.</param>
         /// <returns>PagedResult{TSource}</returns>
-        public static PagedResult<TSource> PageResult<TSource>([NotNull] this IQueryable<TSource> source, int page, int pageSize)
+        public static PagedResult<TSource> PageResult<TSource>([NotNull] this IQueryable<TSource> source, int page, int pageSize, int? rowCount = null)
         {
             Check.NotNull(source, nameof(source));
             Check.Condition(page, p => p > 0, nameof(page));
             Check.Condition(pageSize, ps => ps > 0, nameof(pageSize));
+            Check.Condition(rowCount, rc => rc == null || rc >= 0, nameof(rowCount));
 
             var result = new PagedResult<TSource>
             {
                 CurrentPage = page,
                 PageSize = pageSize,
-                RowCount = Queryable.Count(source)
+                RowCount = rowCount ?? Queryable.Count(source)
             };
 
             result.PageCount = (int)Math.Ceiling((double)result.RowCount / pageSize);

src/System.Linq.Dynamic.Core/Validation/Check.cs

@@ -12,11 +12,9 @@ namespace System.Linq.Dynamic.Core.Validation
     [DebuggerStepThrough]
     internal static class Check
     {
-        [ContractAnnotation("value:null => halt")]
         public static T Condition<T>([NoEnumeration] T value, [NotNull] Predicate<T> condition, [InvokerParameterName] [NotNull] string parameterName)
         {
             NotNull(condition, nameof(condition));
-            NotNull(value, nameof(value));
 
             if (!condition(value))
             {
@@ -136,4 +134,4 @@ public static Type ValidEntityType(Type value, [InvokerParameterName] [NotNull]
             return value;
         }
     }
-}
+}