Merge kb-fileselect-loader-2002 into production

knowledge-base/fileselect-loader.md

@@ -0,0 +1,75 @@
+---
+title: How to Show Progress During File Select
+description: How to show that a file selection process is ongoing? How to display loading progress to users when selecting a large number of files at once?
+type: how-to
+page_title: How to Show Progress Animation When Using FileSelect
+slug: fileselect-kb-loader
+position:
+tags: telerik, blazor, fileselect, loader, progress
+ticketid: 1639447, 1639232
+res_type: kb
+---
+
+## Environment
+
+<table>
+  <tbody>
+    <tr>
+      <td>Product</td>
+      <td>FileSelect for Blazor</td>
+    </tr>
+  </tbody>
+</table>
+
+
+## Description
+
+This KB article answers the following questions:
+
+* How to show progress to end users when using the FileSelect component? Users can select a large number of files at once.
+* How to display a loading animation when handling bigger files in the FileSelect? The selection process is slow so how to indicate that the process is ongoing?
+* How to show users a progress indicator during file selection?
+
+## Solution
+
+You can use the [`Loader`]({%slug loader-overview%}). Set the [Loader `Visible` parameter]({%slug loader-overview%}#loader-parameters) to `true` in the [FileSelect `OnSelect` event]({%slug fileselect-events%}#onselect). The Loader will display while the files are being handled, so that the app is more user-friendly.
+
+When you show the Loader in a method, which is blocking the UI thread with synchronous operations, the Loader may not appear when expected. To avoid this, add a small delay, which helps Blazor refresh the UI during the `OnSelect` handler execution.
+
+Another option is to use the [`LoaderContainer`]({%slug loadercontainer-overview%}). The benefit is that it can overlay the whole page or [cover part of the page that contains the FileSelect]({%slug loadercontainer-overview%}#fill-a-parent-container).
+
+````CSHTML
+<TelerikLoader Visible="@LoaderVisible" />
+
+<TelerikFileSelect OnSelect="@OnSelectHandler" />
+
+@code {
+    private bool LoaderVisible { get; set; }
+
+    private async Task OnSelectHandler(FileSelectEventArgs args)
+    {
+        LoaderVisible = true;
+
+        // allow Blazor to re-render the UI
+        await Task.Delay(1);
+
+        foreach (var file in args.Files)
+        {
+            await HandleFile(file);
+        }
+
+        LoaderVisible = false;
+    }
+
+    private async Task HandleFile(FileSelectFileInfo file)
+    {
+        // some long operation here
+        await Task.Delay(1000);
+    }
+}
+````
+
+## See Also
+
+* [FileSelect Events]({%slug fileselect-events%})
+* [Loader Overview]({%slug loader-overview%})