private string name_ = "default";
 public string Name_
 {
   get { return name_; }
   set
   {
     name_ = value;
     OnPropertyChanged("Name_");
   }
 }

<TextBox x:Name="tbName" Text="{Custom:Binding Name_, Mode=OneWay}" />

Name_="Other text";

set {}

public abstract class BaseViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;                

        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;

            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

    }

<Custom:Window

	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
           xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

<!-- ....................................... -->

<Custom:Window

	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"               "вот"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
           xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
	
	xmlns:Custom="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        "вот"