Get a COMException from WinUI3 when create a grid

Question

When I try to create a Grid, it throw System.Runtime.InteropServices.COMException

var definition = new RowDefinition {Height = GridLength.Auto};
var grid = new Grid { RowDefinitions = { definition, definition } };

StackTrace below:

System.Runtime.InteropServices.COMException (0x800F1000): No installed components were detected.
 at WinRT.DelegateExtensions.DynamicInvokeAbi(Delegate del, Object[] invoke_params)
 at ABI.System.Collections.Generic.IVectorMethods`1.Append(IObjectReference obj, T value)
 at Test..ctor()
 ...

I try to run below code at Immediate Window:

1. var g1 = new Grid{RowDefinitions = { new RowDefinition {Height = GridLength.Auto} } }; No Exception.
2. RowDefinition d = new() {Height = GridLength.Auto}; No Exception.
3. var g3 = new Grid{RowDefinitions = {d}}; COMException.

And I change my code into

RowDefinition Definition() => new RowDefinition {Height = GridLength.Auto};
var grid = new Grid { RowDefinitions = { Definition(), Definition() } };

it can run without exception.

• Raymond Chen: The first one puts the same RowDefinition into the grid twice. The second one creates two RowDefinitions objects. You should have seen the message in the debugger "Element is already the child of another element."
• Raymond Chen: @AndrewKeepCoding The problem is already solved. They just want to know why the solution works.
• Andrew KeepCoding: @RaymondChen Yeah. It seems like it. Thanks!