Add a KB on null reference exception from the GridRowCollection class

knowledge-base/grid-nullreferenceexception-gridrowcollection.md

@@ -0,0 +1,56 @@
+---
+title: NullReferenceException for GridRowCollection
+description: How to fix a null reference exception thrown for the GridRowCollection property of the Telerik Blazor Grid.
+type: troubleshooting
+page_title: NullReferenceException for the Grid GridRowCollection
+slug: grid-kb-nullreferenceexception-gridrowcollection
+position: 
+tags: 
+ticketid: 1643250, 1642910, 1604815, 1574971, 1577863, 1580684
+res_type: kb
+---
+
+## Environment
+<table>
+	<tbody>
+		<tr>
+			<td>Product</td>
+			<td>Grid for Blazor</td>
+		</tr>
+	</tbody>
+</table>
+
+
+## Description
+
+I upgraded the version of the Telerik UI from Blazor components and I get a `NullReferenceException` from the `GridRowCollection` class.
+
+## Error Message
+
+````
+Error: System.NullReferenceException: Object reference not set to an instance of an object. 
+at Telerik.Blazor.Components.Grid.GridRowCollection`1.BuildRenderTree(RenderTreeBuilder __builder)
+````
+
+## Cause
+
+The Telerik UI Grid for Blazor throws a `NullReferenceException` for the `GridRowCollection` property when using both the `Data` parameter and `OnRead` event handler:
+
+<div class="skip-repl"></div>
+
+````CSHTML
+<TelerikGrid Data="@GridData"
+             OnRead="@OnGridRead">
+</TelerikGrid>
+````
+
+## Solution
+
+Remove either the `Data` parameter or the `OnRead` event handler.
+
+## See Also
+
+* [Changes in the `OnRead` event in version 3.0]({%slug changes-in-3-0-0%}#onread)
+* [Common `OnRead` event documentation]({%slug common-features-data-binding-onread%})
+* [How to provide data to Telerik Blazor components]({%slug common-features-data-binding-overview%}#how-to-provide-data)
+