Merge kb-window-focus-2259 into production (#2265)

* kb(window): Add KB for focus on open

* docs(dialog|window): Add KB for focus on open

* Update knowledge-base/window-focus-button-textbox-on-open.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

* Update knowledge-base/window-focus-button-textbox-on-open.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

* Update knowledge-base/window-focus-button-textbox-on-open.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

* Update knowledge-base/window-focus-button-textbox-on-open.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

* Update knowledge-base/window-focus-button-textbox-on-open.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

---------

Co-authored-by: Dimo Dimov <961014+dimodi@users.noreply.github.com>
Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

components/dialog/events.md

@@ -103,4 +103,9 @@ You can use the `VisibleChanged` event to get notifications when the user tries
 
     }
 }
-````
+````
+
+
+## See Also
+
+* [Focus TextBox on Dialog Open]({%slug window-kb-focus-button-textbox-on-open%})

components/window/events.md

@@ -18,6 +18,7 @@ This article explains the events available in the Telerik Window for Blazor:
 * [WidthChanged and HeightChanged](#widthchanged-and-heightchanged)
 * [Action Click](#action-click)
 * [LeftChanged and TopChanged](#leftchanged-and-topchanged)
+
 @[template](/_contentTemplates/common/general-info.md#event-callback-can-be-async) 
 
 
@@ -271,3 +272,4 @@ The `LeftChanged` event fires second, so if you intend to store locations in an
 * [Window Overview]({%slug window-overview%})
 * [Window State]({%slug components/window/size%})
 * [Window Actions]({%slug components/window/actions%})
+* [Focus TextBox on Window Open]({%slug window-kb-focus-button-textbox-on-open%})

knowledge-base/window-focus-button-textbox-on-open.md

@@ -0,0 +1,139 @@
+---
+title: Focus Button or TextBox on Window Open
+description: Learn how to focus a button, input, textbox, or any component when the Telerik Window for Blazor opens.
+type: how-to
+page_title: How to Focus Button or TextBox on Window Open
+slug: window-kb-focus-button-textbox-on-open
+position: 
+tags: telerik, blazor, window, dialog
+ticketid: 1486212, 1513605, 1610413, 1659021
+res_type: kb
+---
+
+## Environment
+
+<table>
+    <tbody>
+        <tr>
+            <td>Product</td>
+            <td>Dialog for Blazor, <br /> Window for Blazor</td>
+        </tr>
+    </tbody>
+</table>
+
+
+## Description
+
+This KB article answers the following questions:
+
+* How to set default focus to a TextBox or a Button in a Telerik UI for Blazor Window?
+* How to focus a button or a textbox inside a Window when the Window is made visible?
+* How to focus a component after the Window opens? The JavaScript call is made before the Window actually shows, so the focusable element is `null`.
+* How do you set focus on an input element in a Window, so that the user doesn't have to use their mouse?
+
+
+## Solution
+
+To focus any element or component in the [Telerik UI Window for Blazor]({%slug dialog-overview%}), follow the steps below. They are also applicable for the [Dialog component]({%slug dialog-overview%}).
+
+1. To focus a Telerik UI for Blazor component, [set the `@ref` attribute to obtain the component's reference]({%slug components/textbox/overview%}#textbox-reference-and-methods).
+1. Raise a `bool` flag when showing the Window.
+1. Check the boolean flag's value in `OnAfterRenderAsync()`.
+1. Use a small `Task.Delay()` to wait for the Window to display and gain focus. Without a delay, the focusable component will either not exist yet, or the Window will steal the focus.
+1. Focus the desired button, textbox, or input component. If it's a Telerik UI for Blazor component, use the [`FocusAsync()` method]({%slug inputs-kb-focus%}).
+
+>caption Focus a component on Dialog or Window open
+
+````CSHTML
+<TelerikButton OnClick="@ShowWindow">Show Window and Focus Button</TelerikButton>
+<TelerikButton OnClick="@ShowDialog">Show Dialog and Focus TextBox</TelerikButton>
+
+<TelerikWindow @bind-Visible="@WindowVisible"
+               Modal="true">
+    <WindowActions>
+        <WindowAction Name="Close" />
+    </WindowActions>
+    <WindowTitle>
+        Window
+    </WindowTitle>
+    <WindowContent>
+        <p>This Button is now focused:</p>
+        <TelerikButton @ref="@ButtonRef"
+                       OnClick="@OnWindowButtonClick">
+            Click Me
+        </TelerikButton>
+        <p><code>StringValue</code>: @StringValue</p>
+    </WindowContent>
+</TelerikWindow>
+
+<TelerikDialog @bind-Visible="@DialogVisible"
+               Title="Dialog"
+               ButtonsLayout="@DialogButtonsLayout.End">
+    <DialogContent>
+        <TelerikTextBox @ref="@TextBoxRef" @bind-Value="@StringValue" />
+    </DialogContent>
+    <DialogButtons>
+        <TelerikButton OnClick="@( () => DialogVisible = false )">Close</TelerikButton>
+    </DialogButtons>
+</TelerikDialog>
+
+@code {
+    private TelerikButton? ButtonRef { get; set; }
+    private TelerikTextBox? TextBoxRef { get; set; }
+
+    private string StringValue { get; set; } = string.Empty;
+
+    private bool WindowVisible { get; set; }
+    private bool DialogVisible { get; set; }
+
+    private bool ShouldFocusButton { get; set; }
+    private bool ShouldFocusTextBox { get; set; }
+
+    private void ShowWindow()
+    {
+        WindowVisible = true;
+        ShouldFocusButton = true;
+    }
+
+    private void ShowDialog()
+    {
+        StringValue = string.Empty;
+        DialogVisible = true;
+        ShouldFocusTextBox = true;
+    }
+
+    private void OnWindowButtonClick()
+    {
+        var now = DateTime.Now;
+        StringValue = $"{now.ToString("HH:mm:ss")}.{now.Millisecond}";
+    }
+
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (ShouldFocusButton && ButtonRef != null)
+        {
+            ShouldFocusButton = false;
+            // Wait for the Window to render and gain focus.
+            await Task.Delay(200);
+            await ButtonRef.FocusAsync();
+        }
+
+        if (ShouldFocusTextBox && TextBoxRef != null)
+        {
+            ShouldFocusTextBox = false;
+            // Wait for the Dialog to render and gain focus.
+            await Task.Delay(200);
+            await TextBoxRef.FocusAsync();
+        }
+
+        await base.OnAfterRenderAsync(firstRender);
+    }
+}
+````
+
+
+## See Also
+
+* [Dialog Overview]({%slug dialog-overview%})
+* [Window Overview]({%slug window-overview%})
+* [Focus Telerik Input Components]({%slug inputs-kb-focus%})