Issue in WinUI TextBox style when overriding

@Castorix31 That did the trick. Thanks for the solution. Can you please add this solution to your first reply, so that i can mark this as an answer.

I will try to "convert to answer" this comment if it is more relevant than my answer...
(just did it, it seems to work (I had never tried this option...))

Solution works good for textbox, but failed for ComboBox in my real project. In my sample project, i tried the same for combo box, where it failed first time, but works good after that. Can you please help on this?

I tested in a C# WindowsAppSDK test project with a style from MS and it works for me (Windows 10 21H1) :

  <Style TargetType="ComboBox" x:Key="ComboBoxStyle" BasedOn="{StaticResource DefaultComboBoxStyle}">
                <Setter Property="Width" Value="200"/>
                <Setter Property="Height" Value="30"/>
                <Setter Property="Margin" Value="4"/>
                <Setter Property="FontSize" Value="14"/>
                <Setter Property="Background">
                    <Setter.Value>
                        <LinearGradientBrush StartPoint="0,0.5" EndPoint="1,0.5">
                            <GradientStop Color="White" Offset="0.0"/>
                            <GradientStop Color="LightBlue" Offset="0.5"/>
                            <GradientStop Color="Navy" Offset="1"/>
                        </LinearGradientBrush>
                    </Setter.Value>
                </Setter>
            </Style>

@Castorix31 I have tried another sample project. I have added a new class library and added the style in a resource dictionary file in it. When referring this class library in my main project and using the style, the exception is thrown.

UPDATE: I have found the reason. XamlControlsResources is not merged to the resource dictionary in my class library. Once added it is working fine. As i am having multiple resource dictionary files, Do i need to add XamlControlsResources in all the files ??