DataGrid: Fix filter and several other bugs (#4942, #4924, #4921, #4551…

…) (#5093)

src/MudBlazor.UnitTests.Viewer/TestComponents/DataGrid/DataGridSequenceContainsNoElementsTest.razor

@@ -0,0 +1,32 @@
+@namespace MudBlazor.UnitTests.TestComponents
+<MudPopoverProvider></MudPopoverProvider>
+
+<MudDataGrid Items="@_items" Filterable="true">
+    <Columns>
+        <Column T="Model" Field="@nameof(Model.Id)" />
+        <Column T="Model" Field="@nameof(Model.Name)" />
+    </Columns>
+</MudDataGrid>
+
+@code {
+    private IEnumerable<Model> _items = new List<Model>()
+    {
+        new Model("B"), 
+        new Model("A"), 
+        new Model("C"),
+        new Model("C")
+    };
+
+    public class Model
+    {
+        public Guid Id { get; set; }
+        public string Name { get; set; }
+
+        public Model(string name)
+        {
+            Id = Guid.NewGuid();
+            Name = name;
+        }
+    }
+
+}

src/MudBlazor.UnitTests/Components/DataGridTests.cs

@@ -2612,5 +2612,14 @@ public async Task DataGridCellContextTest()
             cell.cellContext.Actions.SetSelectedItem(true);
             cell.cellContext.IsSelected.Should().Be(true);
         }
+
+        [Test]
+        public async Task DataGridSequenceContainsNoElementsTest()
+        {
+            var comp = Context.RenderComponent<DataGridSequenceContainsNoElementsTest>();
+            var dataGrid = comp.FindComponent<MudDataGrid<DataGridSequenceContainsNoElementsTest.Model>>();
+
+            // This test will result in an error if the 'sequence contains no elements' issue is present.
+        }
     }
 }

src/MudBlazor/Components/DataGrid/Column.cs

@@ -279,7 +279,7 @@ protected override void OnInitialized()
                     Field = Field,
                     FieldType = FieldType,
                     Title = Title,
-                    Operator = operators.First()
+                    Operator = operators.FirstOrDefault()
                 };
             }