MultiBinding

I wanted to control the IsEnabled property of a Button based on the properties of two other controls.
Specifically I wanted to only enable the LogIn button if both the Site combobox and UserName textbox had a value available.

I created a MultiBinding for the Button like this:

<Button.IsEnabled>

   <MultiBinding Converter="{StaticResource loginConverter}">

      <Binding ElementName="xSite" Path="SelectedIndex"/>

      <Binding ElementName="xUsername" Path="Text"/>

   </MultiBinding>

</Button.IsEnabled>

And a IMultiValueConverter like this:

public class LoginConverter : IMultiValueConverter

{

   public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)

   {

      // SelectedIndex of the ComboBox

      int selectedIndex = (int)values[0];

      // Length of Text in TextBox

      int selectedLength = ((string)values[1]).Length;

      // Only enable Button if both Combo and TextBox have data

      if (selectedIndex == -1 || selectedLength==0)

      {

         return false;

      }

      else

      {

         return true;

      }

   }

   public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)

   {

      throw new NotImplementedException();

   }

}

The array of object[] values are presented in the same order as the Bindings within the MultiBinding.

Finally here is an example of using MultiBinding with StringFormat.