Access Class Member in XAML Code

Question

How to preform the following result in a my WPF project.

C# Code Behind

public class Test
{
    public int a;
}

Custom Control Code Behind

public class myControl : Control
{
    public Test myVar { get; set; }
}

Xaml Code

<myControl myVar.a=2/>

For Example, Using this Code like TextBlock Class in under code:

<TextBox TextBlock.FontFamily="12"/>

Answer 1

The example you give with TextBlock

<TextBox TextBlock.FontFamily="12"/>

is a different case, because TextBlock is not a property of TextBox.

Here you are setting a so called attached property.

Following your example, you would have to write the Test class as follows:

using System.Windows;

namespace WpfApp1
{
  public class Test
  {
    public static readonly DependencyProperty aProperty
      = DependencyProperty.RegisterAttached ( "a",
                                              typeof(int),
                                              typeof(Test),
                                              new PropertyMetadata(0) ) ;

    public static int Geta ( DependencyObject obj )
    {
      return (int)obj.GetValue(aProperty);
    }

    public static void Seta ( DependencyObject obj, int value )
    {
      obj.SetValue(aProperty, value);
    }
  }
}

You can then set it in XAML as follows:

<local:myControl local:Test.a="2" />

Note that I am not using your property myVar at all.

If this is what you want, I suggest you do some background reading on attached properties.