Option 1: Using Task.Delay(1)
- Use an async method.
- Use
await Task.Delay(1)
orawait 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 1 is a simple solution that runs ok but looks like a trick.
Option 2: Using Task.Run() (not for WebAssembly)
On January’2020. @Ed Charbeneau published BlazorPro.Spinkit project enclosing long processes into task to don’t block the thread:
Ensure your LongOperation()
is a Task
, if it is not, enclose it into a Task
and await for it:
async Task AsyncLongOperation() // this is an async task
{
spinning=true;
await Task.Run(()=> LongOperation()); //<--here!
currentCount++;
spinning=false;
}
Effect
Spinner and server side prerendering
Because Blazor Server apps use pre-rendering the spinner will not appear, to show the spinner the long operation must be done in OnAfterRender.
Use OnAfterRenderAsync over OnInitializeAsync to avoid a delayed server-side rendering
// Don't do this
//protected override async Task OnInitializedAsync()
//{
// await LongOperation();
//}
protected override async Task OnAfterRenderAsync(bool firstRender)
{
if (firstRender)
{
await Task.Run(()=> LongOperation());//<--or Task.Delay(0) without Task.Run
StateHasChanged();
}
}
More samples
Learn more about how to write nice spinner you can learn from open source project BlazorPro.Spinkit, it contains clever samples.