How Can I Dynamically Show User Feedback During Long-Running API Calls in Blazor?

Dynamically Displaying User Feedback during API Calls in Blazor

In Blazor, handling long-running API calls requires providing feedback to users, such as displaying a wait cursor or a "spinner" image. This article presents two approaches for achieving this:

Option 1: Using Task.Delay(1)

• Create an async method.
• Use await Task.Delay(1); or await Task.Yield(); to flush changes.

private async Task AsyncLongFunc()    // this is an async task
{
    spinning=true;
    await Task.Delay(1);      // flushing changes. The trick!!
    LongFunc();               // non-async code
    currentCount++;
    spinning=false;
    await Task.Delay(1);      // changes are flushed again    
}

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

Create a Task that encloses the long operation:

async Task AsyncLongOperation()    // this is an async task
{
    spinning=true;
    await Task.Run(()=> LongOperation());  //<--here!
    currentCount++;
    spinning=false;
}

Effect on Pre-rendering

In Blazor Server apps, the spinner may not appear due to pre-rendering. To resolve this, perform the long operation in OnAfterRender instead of OnInitializedAsync.

protected override async Task OnAfterRenderAsync(bool firstRender)
{
    if (firstRender)
    {            
        await Task.Run(()=> LongOperation());//<--or Task.Delay(0) without Task.Run
        StateHasChanged();
    }
}

For additional insights into effective spinner implementations, explore the open-source project BlazorPro.Spinkit.

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