PaginateViaPrimaryKey: handle the case of emtpy key list (#350)

Author: AlekseyMartynov

net/DevExtreme.AspNet.Data.Tests/PaginateViaPrimaryKeyTests.cs

@@ -99,6 +99,21 @@ public void RequiresPrimaryKey() {
             Assert.True(error is InvalidOperationException);
         }
 
+        [Fact]
+        public void Bug349() {
+            // https://github.com/DevExpress/DevExtreme.AspNet.Data/issues/349
+
+            var loadResult = DataSourceLoader.Load(new[] { new { ID = 1 } }, new SampleLoadOptions {
+                PaginateViaPrimaryKey = true,
+                PrimaryKey = new[] { "ID" },
+                RequireTotalCount = true,
+                Skip = 1,
+                Take = 1
+            });
+
+            Assert.Empty(loadResult.data);
+        }
+
         static string DataToString(object data) {
             return JsonConvert.SerializeObject(data).Replace("\"", "");
         }

net/DevExtreme.AspNet.Data/DataSourceExpressionBuilder.cs

@@ -35,8 +35,13 @@ Expression BuildCore(Expression expr, bool paginate = false, bool isCountQuery =
             var queryableType = typeof(Queryable);
             var genericTypeArguments = new[] { typeof(T) };
 
-            if(filterOverride != null || _context.HasFilter)
-                expr = Expression.Call(queryableType, "Where", genericTypeArguments, expr, Expression.Quote(new FilterExpressionCompiler<T>(_guardNulls, _context.UseStringToLower).Compile(filterOverride ?? _context.Filter)));
+            if(filterOverride != null || _context.HasFilter) {
+                var filterExpr = filterOverride != null && filterOverride.Count < 1
+                    ? Expression.Lambda(Expression.Constant(false), Expression.Parameter(typeof(T)))
+                    : new FilterExpressionCompiler<T>(_guardNulls, _context.UseStringToLower).Compile(filterOverride ?? _context.Filter);
+
+                expr = Expression.Call(queryableType, "Where", genericTypeArguments, expr, Expression.Quote(filterExpr));
+            }
 
             if(!isCountQuery) {
                 if(!remoteGrouping) {