Update text box from another class

Update text box from another class For example, you need to update text box, but from another class. In that case, best would be if you provide class where is property which is bounded to the text box, something like:

public class SettingTheProperty
{
	public SettingTheProperty(SetPropertyViewModel spvm)
	{
		spvm.DisplayText = "SettingTheProperty";
	}
}

Then call from main class would be like (in my case it is SetPropertyViewModel):

private void ShowMessage()
{
	SettingTheProperty stp = new SettingTheProperty(this);
}

Example project you can download from here.