docs(Window): add kb for backdrop blur

knowledge-base/window-backdrop-blur.md

@@ -0,0 +1,69 @@
+---
+title: Apply a backdrop filter with a blur effect to the Modal Window background
+description: How to apply a backdrop filter with a blur effect to the background content of the Modal Window.
+type: how-to
+page_title: Apply a backdrop filter with a blur effect to the Modal Window background
+slug: window-kb-backdrop-blur
+position: 
+tags: 
+ticketid: 1642061
+res_type: kb
+---
+
+## Environment
+<table>
+	<tbody>
+		<tr>
+			<td>Product</td>
+			<td>Window for Blazor</td>
+		</tr>
+	</tbody>
+</table>
+
+## Description
+
+* How do I blur the background in Windows?
+* Is it possible to apply a backdrop filter with a blur effect on the background content of the Window?
+
+## Solution
+
+Override the built-in CSS styles of the background with the code below to adjust the blur amount. 
+
+>caption This code will affect all modal Dialogs and Windows on the web page.
+
+````CSHTML
+<style>
+    div.k-overlay {
+        /* prerequisites to make the blurring work with this CSS class */
+        opacity: 1;
+        background-color: transparent;
+        /* blurring itself */
+        -webkit-backdrop-filter: blur(4px); /* Safari */
+        backdrop-filter: blur(4px);
+    }
+</style>
+
+<TelerikWindow @bind-Visible="@WindowIsVisible"
+               Modal="true">
+    <WindowTitle>
+        Product Details
+    </WindowTitle>
+    <WindowContent>
+        <div class="p-4">
+            <h2>Product Name: Widget X</h2>
+            <p>Description: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed ac odio velit. Integer vel turpis vestibulum, tincidunt lacus at, rutrum sapien.</p>
+            <p>Price: $49.99</p>
+            <p>Availability: In Stock</p>
+        </div>
+    </WindowContent>
+    <WindowActions>
+        <WindowAction Name="Close" />
+    </WindowActions>
+</TelerikWindow>
+
+<TelerikButton OnClick="@( () => WindowIsVisible = !WindowIsVisible )">Show Product Details</TelerikButton>
+
+@code {
+    private bool WindowIsVisible { get; set; }
+}
+````