[DataGrid ] Refactor DataGrid virtualization and async handling; add tests by miguelhasse · Pull Request #4885 · microsoft/fluentui-blazor

miguelhasse · 2026-05-21T17:15:38Z

Pull Request

📖 Description

Solution and Test Project Enhancements:

Added new test projects for EntityFrameworkAdapter and ODataAdapter to the solution, improving test coverage and reliability.
Updated the solution to support additional build configurations (x64, x86) for all projects, enhancing compatibility across platforms.

DataGrid Virtualization and Loading Logic:

Refined the virtualized data loading logic in FluentDataGrid.razor and its code-behind to ensure that data is only loaded when the Virtualize component is ready, and to prevent unnecessary or duplicate data loads during the initial render. [1] [2] [3]
Removed the unused _renderEmptyContent delegate and related code, simplifying the component. [1] [2]

Async Operation and Cancellation Improvements:

Improved async data loading by properly handling cancellation tokens, including catching cancellation exceptions and returning default values when operations are cancelled. This prevents unnecessary errors and ensures the UI remains responsive. [1] [2] [3]
Fixed a bug in pagination logic by correcting how the count variable is calculated when pagination is enabled.

Entity Framework Async Executor:

Enhanced the EntityFrameworkAsyncQueryExecutor to properly propagate and handle cancellation tokens for both CountAsync and ToArrayAsync methods, and to ensure resources are released correctly even when operations are cancelled. [1] [2]

These changes collectively improve the maintainability, testability, and reliability of the DataGrid component and its supporting infrastructure.

🎫 Issues

👩‍💻 Reviewer Notes

The following examples can be used to test behavior enhancements:

AdventureWorks
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✅ Checklist

General

I have added tests for my changes.
I have tested my changes.
I have updated the project documentation to reflect my changes.
I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

I have added a new component
I have added Unit Tests for my new component
I have modified an existing component
I have validated the Unit Tests for an existing component

- Always render Virtualize component; remove empty content logic for virtualization. - Remove `_renderEmptyContent` field and initialization. - Improve data loading: avoid loading if Virtualize is not ready, set `Loading` to false. - Respect cancellation tokens in async delays and query execution. - Fix pagination count calculation to prevent negative values. - Only call `ToArrayAsync` if count > 0; check for cancellation. - Update `EntityFrameworkAsyncQueryExecutor` and `ODataAsyncQueryExecutor` to handle cancellation and exceptions more robustly.

Added test projects for EntityFramework and OData adapters, updated solution file, and exposed internals for testing. Improved ODataAsyncQueryExecutor to handle cancellation and nulls. Added unit tests covering normal, cancellation, disposal, and exception scenarios.

Copilot

Pull request overview

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Copilot was unable to run its full agentic suite in this review.

Adds test coverage for DataGrid async query executors (Entity Framework + OData) and adjusts cancellation/paging/virtualization behavior to avoid unnecessary work and better handle canceled operations.

Changes:

Added new test projects and test suites for EF and OData async query executors.
Updated EF + OData query executors to better handle cancellation and exceptions.
Refactored FluentDataGrid refresh/virtualize flow and adjusted paging/item loading logic.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/Extensions/DataGrid.ODataAdapter/ODataAsyncQueryExecutorTests.cs	Adds unit tests for OData async executor support detection and cancellation behavior.
tests/Extensions/DataGrid.ODataAdapter/Microsoft.FluentUI.AspNetCore.Components.DataGrid.ODataAdapter.Tests.csproj	Introduces a dedicated OData adapter test project with required packages.
tests/Extensions/DataGrid.EntityFrameworkAdapter/Microsoft.FluentUI.AspNetCore.Components.DataGrid.EntityFrameworkAdapter.Tests.csproj	Introduces a dedicated EF adapter test project with required packages.
tests/Extensions/DataGrid.EntityFrameworkAdapter/EntityFrameworkAsyncQueryExecutorTests.cs	Adds EF executor tests, including cancellation/dispose and ignore-exception paths.
src/Extensions/DataGrid.ODataAdapter/ODataAsyncQueryExecutor.cs	Improves cancellation handling and makes count conversion checked.
src/Extensions/DataGrid.ODataAdapter/Microsoft.FluentUI.AspNetCore.Components.DataGrid.ODataAdapter.csproj	Adds `InternalsVisibleTo` for the new OData adapter test assembly.
src/Extensions/DataGrid.EntityFrameworkAdapter/Microsoft.FluentUI.AspNetCore.Components.DataGrid.EntityFrameworkAdapter.csproj	Adds `InternalsVisibleTo` for the new EF adapter test assembly.
src/Extensions/DataGrid.EntityFrameworkAdapter/EntityFrameworkAsyncQueryExecutor.cs	Passes cancellation into the lock wait and swallows pre-cancelled operations.
src/Core/Components/DataGrid/FluentDataGrid.razor.cs	Changes refresh flow for virtualization and modifies delay/paging and async-query execution logic.
src/Core/Components/DataGrid/FluentDataGrid.razor	Always renders `Virtualize` when `Virtualize` is enabled (removes “empty content” branch).
Microsoft.FluentUI.sln	Adds the new test projects and expands solution configurations/platforms.

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        {
            startIndex += Pagination.CurrentPageIndex * Pagination.ItemsPerPage;
-            count = Math.Min(request.Count, Pagination.ItemsPerPage - request.StartIndex);
+            count = Math.Max(request.Count, Math.Min(0, Pagination.ItemsPerPage - request.StartIndex));


vnbaaij · 2026-05-21T18:35:18Z

                    @if (Virtualize)
                    {
-                        if (_internalGridContext.TotalItemCount == 0)
-                        {
-                            @_renderEmptyContent
-                        }
-                        else
-                        {
-                            <Virtualize @ref="@_virtualizeComponent"
-                                        TItem="(int RowIndex, TGridItem Data)"
-                                        ItemSize="@ItemSize"
-                                        OverscanCount="@OverscanCount"
-                                        ItemsProvider="@ProvideVirtualizedItemsAsync"
-                                        ItemContent="@(item => builder => RenderRow(builder, item.RowIndex, item.Data))"
-                                        Placeholder="@(placeholderContext => builder => RenderPlaceholderRow(builder, placeholderContext))"
-                                        SpacerElement="tr"/>
-                        }
+                        <Virtualize @ref="@_virtualizeComponent"
+                                    TItem="(int RowIndex, TGridItem Data)"
+                                    ItemSize="@ItemSize"
+                                    OverscanCount="@OverscanCount"
+                                    ItemsProvider="@ProvideVirtualizedItemsAsync"
+                                    ItemContent="@(item => builder => RenderRow(builder, item.RowIndex, item.Data))"
+                                    Placeholder="@(placeholderContext => builder => RenderPlaceholderRow(builder, placeholderContext))"
+                                    SpacerElement="tr"/>


Yeah, this changes the current behavior of the grid significantly and cannot be done this way

Yeah completely right. I'll do it differently in a way that works for all scenarios.

+        catch (DataServiceQueryException ex) when (ex.InnerException is OperationCanceledException oce)
+        {
+            ExceptionDispatchInfo.Capture(oce).Throw();
+            throw; // unreachable; satisfies compiler
+        }


miguelhasse · 2026-05-22T09:01:03Z

-        => [.. await ExecuteAsync(queryable, cancellationToken)];
+    {
+        var response = await ExecuteAsync(queryable, cancellationToken);
+        return response is null ? default! : [.. response];


Good suggestion.

        => queryable.Provider is IAsyncQueryProvider;

    /// <inheritdoc />
+    /// 


vnbaaij · 2026-05-21T17:38:19Z

Hi Miguel,

Valid changes I presume, but we will not merge this in it's current form. Don't want to be blunt but actually have a couple of reasons for it:

We are focusing solely on v5 (for a while already). I do not want to release (such) big changes for v4 anymore.
The changes combined is too much to deliver in 1 PR. This should be cut into several separate PRs.
I'm questioning some of the changes presented with this and miss the understanding of why the changes are made.

Let's work together to see if and how we can do this for v5.

miguelhasse · 2026-05-22T09:00:22Z

Hi Miguel,

Valid changes I presume, but we will not merge this in it's current form. Don't want to be blunt but actually have a couple of reasons for it:

We are focusing solely on v5 (for a while already). I do not want to release (such) big changes for v4 anymore.

The changes combined is too much to deliver in 1 PR. This should be cut into several separate PRs.

I'm questioning some of the changes presented with this and miss the understanding of why the changes are made.

Let's work together to see if and how we can do this for v5.

Totally understandable, and I would be happy to work on this with you for v5.

Some of the changes here are hardening enhancements, but the changes involving Virtualize mode are fixes to broken behavior when we switch back and forth between virtual and non-virtual when items are provided by IAsyncQueryProvider.

I do have one question for you... what's plan on moving IAsyncQueryProvider extension implementations to v5?

- Render empty content when no items in virtualized DataGrid - Fix pagination count calculation logic - Refine exception handling in EF async executor - Simplify and annotate OData async query methods - Remove redundant OperationCanceledException catch blocks

Tests now expect OperationCanceledException for pre-cancelled tokens instead of default values. Added tests for disposal and exception predicate logic in EntityFrameworkAsyncQueryExecutor. Enhanced ThrowingQueryable<T> to implement IAsyncEnumerable<T> for better exception path coverage.

miguelhasse added 2 commits May 21, 2026 08:45

miguelhasse requested a review from vnbaaij as a code owner May 21, 2026 17:15

Copilot AI review requested due to automatic review settings May 21, 2026 17:15

miguelhasse requested a review from dvoituron as a code owner May 21, 2026 17:15

Copilot AI reviewed May 21, 2026

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miguelhasse added 2 commits May 22, 2026 11:20

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[DataGrid ] Refactor DataGrid virtualization and async handling; add tests#4885

[DataGrid ] Refactor DataGrid virtualization and async handling; add tests#4885
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miguelhasse:datagrid-async-query-executor-and-virtualize-enhancements

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miguelhasse commented May 21, 2026

Pull Request

📖 Description

🎫 Issues

👩‍💻 Reviewer Notes

✅ Checklist

General

Component-specific

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vnbaaij May 21, 2026

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vnbaaij commented May 21, 2026

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