PaginateViaPrimaryKey: enable for Skip=0 (#370)

Author: AlekseyMartynov

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

@@ -74,18 +74,23 @@ public void MultiKey() {
         }
 
         [Fact]
-        public void NotUsedWoSkip() {
+        public void ActiveForFirstPage() {
+            var data = new[] {
+                new { ID = 123 }
+            };
+
             var loadOptions = new SampleLoadOptions {
+                SuppressGuardNulls = true,
+                PrimaryKey = new[] { "ID" },
                 PaginateViaPrimaryKey = true,
+
+                Skip = 0,
                 Take = 123
             };
 
-            DataSourceLoader.Load(new object[0], loadOptions);
+            DataSourceLoader.Load(data, loadOptions);
 
-            Assert.All(
-                loadOptions.ExpressionLog,
-                i => Assert.DoesNotContain(".Select(", i)
-            );
+            Assert.Contains(".Select(obj => new AnonType`1", loadOptions.ExpressionLog[0]);
         }
 
         [Fact]

net/DevExtreme.AspNet.Data/DataSourceLoaderImpl.cs

@@ -66,7 +66,7 @@ public LoadResult Load() {
 
                 Expression loadExpr;
 
-                if(!deferPaging && Context.PaginateViaPrimaryKey && Context.Skip > 0) {
+                if(!deferPaging && Context.PaginateViaPrimaryKey) {
                     if(!Context.HasPrimaryKey) {
                         throw new InvalidOperationException(nameof(DataSourceLoadOptionsBase.PaginateViaPrimaryKey)
                             + " requires a primary key."