How to add content from C# to XAML

I have used a litle XamarinForms before and then i did a
naming to be able to point the c# code to it.

   <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
   xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
   x:Class="MauiTest.MainPage"
   BackgroundColor="{DynamicResource SecondaryColor}">

    <StackLayout x:name="_stacklayoutname">     
    <Label Text="" x:Name="_Lable"/>
    </StackLayout>
</ContentPage>

And then i did like this in the MainPage.xaml.cs

   public MainPage()
    {
        InitializeComponent();
        _stacklayoutname.Children.Add(new Label { Text = "TEST" });
        _Lable.Text = "TEST";
    }

now it get this, but i can change the _Lable to "Text".
how can i point to a stacklayout.

Severity    Code    Description Project File    Line    Suppression State
Error   CS0103  The name '_stacklayoutname' does not exist in the current context   MauiTest (net6.0-android), MauiTest (net6.0-ios), MauiTest (net6.0-maccatalyst), MauiTest (net6.0-windows10.0.19041)    *** 11  Active

>Solution :

this is wrong

<StackLayout x:name="_stacklayoutname">  

it should be

<StackLayout x:Name="_stacklayoutname">