How Can I Prevent UI Blocking During API Calls in Blazor?

Non-Blocking UI Updates During API Calls in Blazor

When making API calls in a Blazor application, it's crucial to provide feedback to users, indicating that an action is in progress. This can be achieved by displaying a spinner or wait cursor.

Option 1: Using Task.Delay(1)

This method involves running an asynchronous task and including await Task.Delay(1) within it. This allows changes to be flushed and the UI to be updated before the long-running operation begins.

private async Task AsyncLongFunc()
{
    spinning = true;
    await Task.Delay(1); // Flushing changes
    LongFunc(); // Non-async code
    currentCount++;
    spinning = false;
    await Task.Delay(1); // Flushing changes again
}

Option 2: Using Task.Run() (Not for WebAssembly)

This approach involves enclosing long-running operations within a task, ensuring it doesn't block the main thread.

async Task AsyncLongOperation()
{
    spinning = true;
    await Task.Run(() => LongOperation()); // Enclose in a task
    currentCount++;
    spinning = false;
}

Effects and Limitations

Both methods effectively display a spinner during API calls. However, the spinner may not appear if the server-side pre-rendering is enabled in Blazor Server apps. To resolve this, long operations should be handled in the OnAfterRender event.

Sample Projects

Explore the open-source project BlazorPro.Spinkit for more examples and techniques for implementing spinners in your Blazor applications.

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