Question

I have a UserControl like this:

<UserControl x:Class="MySample.customtextbox"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="20" d:DesignWidth="300">
<Grid>
       <TextBox x:Name="Ytextbox"  Background="Yellow"/> 
</Grid>
 </UserControl>

I want use my control in mvvm pattern …i want that i can bind a property in my viewmodel to Ytextbox Text Property

<CT:customtextbox  ?(Ytextbox)Text ="{binding  mypropertyinviewmodel}"/>

…how can I do it?

Answer 1

You should create a property on the UserControl and bind that internally to the TextBox’s text.

i.e.

<UserControl Name="control" ...>
    <!-- ... -->
        <TextBox Text="{Binding Text, ElementName=control}"
                 Background="Yellow"/>

public class customtextbox : UserControl
{
    public static readonly DependencyProperty TextProperty =
        TextBox.TextProperty.AddOwner(typeof(customtextbox));
    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }
}

Usage:

<CT:customtextbox Text="{Binding  mypropertyinviewmodel}"/>

(Do not set the DataContext in the UserControl to itself unless you want all external bindings which expect the DataContext to be inherited to fail, use ElementName or RelativeSource for internal bindings)