RadzenTabs: ensure render state is restored when tab event handlers throw

Follow-up to the #2558 fix. In SelectTab the StateHasChanged call was skipped
if Change/SelectedIndexChanged threw, leaving the component stale (multiple
tabs visually active); in SelectTabOnClient a throw left shouldRender stuck at
false, blocking all further renders. Wrap both in finally so the render state
is always restored. Addresses review feedback on commit df1dfa7.

Fixes #2558

Author: enchev

Radzen.Blazor.Tests/TabsTests.cs

@@ -230,6 +230,27 @@ public void Tabs_EscapeKeyDownInPanelContent_UpdatesPropagation()
             Assert.True(component.RenderCount > renderCountBefore);
         }
 
+        [Fact]
+        public void Tabs_ChangeHandlerThrows_StillRendersSelectedTab()
+        {
+            using var ctx = new TestContext();
+
+            var component = ctx.RenderComponent<RadzenTabs>(parameters => parameters
+                .Add(p => p.SelectedIndex, 0)
+                .Add(p => p.Change, (int _) => throw new System.InvalidOperationException("boom"))
+                .Add(p => p.Tabs, TabsFragmentWithContent(("First", "First-Content"), ("Second", "Second-Content")))
+            );
+
+            Assert.Contains("First-Content", component.Markup);
+
+            var secondTab = component.FindAll("button[role='tab']")[1];
+            var ex = Record.Exception(() => secondTab.Click());
+
+            Assert.NotNull(ex);
+            Assert.Contains("Second-Content", component.Markup);
+            Assert.DoesNotContain("First-Content", component.Markup);
+        }
+
         [Fact]
         public void Tabs_NonNavigationKeyDown_DoesNotBlockSubsequentRenders()
         {

Radzen.Blazor/RadzenTabs.razor.cs

@@ -210,22 +210,27 @@ internal async Task SelectTab(RadzenTabsItem tab, bool raiseChange = false)
 
             SetFocusedIndex();
 
-            if (raiseChange)
+            try
             {
-                await Change.InvokeAsync(selectedIndex);
+                if (raiseChange)
+                {
+                    await Change.InvokeAsync(selectedIndex);
 
-                await SelectedIndexChanged.InvokeAsync(selectedIndex);
+                    await SelectedIndexChanged.InvokeAsync(selectedIndex);
 
-                try
-                {
-                    await Element.FocusAsync(preventScroll: true);
-                }
-                catch (JSDisconnectedException)
-                {
+                    try
+                    {
+                        await Element.FocusAsync(preventScroll: true);
+                    }
+                    catch (JSDisconnectedException)
+                    {
+                    }
                 }
             }
-
-            StateHasChanged();
+            finally
+            {
+                StateHasChanged();
+            }
         }
 
         /// <inheritdoc />
@@ -342,9 +347,15 @@ internal async System.Threading.Tasks.Task SelectTabOnClient(RadzenTabsItem tab)
                 }
 
                 shouldRender = false;
-                await Change.InvokeAsync(selectedIndex);
-                await SelectedIndexChanged.InvokeAsync(selectedIndex);
-                shouldRender = true;
+                try
+                {
+                    await Change.InvokeAsync(selectedIndex);
+                    await SelectedIndexChanged.InvokeAsync(selectedIndex);
+                }
+                finally
+                {
+                    shouldRender = true;
+                }
 
                 try
                 {