Prevent unwanted GroupBy call for GroupSummary without Group (#432)

Author: AlekseyMartynov

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

@@ -177,6 +177,20 @@ public void GroupSummaryAndTotalCount() {
             Assert.Equal(2, result.totalCount);
         }
 
+        [Fact]
+        public void GroupSummary_NoGroups() {
+            var loadOptions = new SampleLoadOptions {
+                RemoteGrouping = true,
+                GroupSummary = new[] {
+                    new SummaryInfo { Selector = "any" }
+                }
+            };
+
+            DataSourceLoader.Load(new object[0], loadOptions);
+
+            Assert.DoesNotContain(loadOptions.ExpressionLog, line => line.Contains("GroupBy"));
+        }
+
         [Fact]
         public void NotUsedIfTotalCountOnly() {
             var data = new[] {

net/DevExtreme.AspNet.Data/DataSourceLoadContext.cs

@@ -232,7 +232,7 @@ partial class DataSourceLoadContext {
 
         public bool HasTotalSummary => !IsEmpty(TotalSummary);
 
-        public bool HasGroupSummary => !IsEmpty(GroupSummary);
+        public bool HasGroupSummary => HasGroups && !IsEmpty(GroupSummary);
 
         public bool SummaryIsTotalCountOnly {
             get {