Do you mean that you want to bind a variable (not a property) to ComboBox.SelectedIndex? If so, I think that the better method to do this is bind a property to ComboBox.SelectedItem. The following example shows how to bind a property to the ComboBox.SelectedItem. If you want to have more functionality from the binding, you should have the property is a dependency property.
Code Snippet
<Window x:Class="LearningSolution.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:system="clr-namespace:System;assembly=mscorlib"
xmlns:local="clr-namespace:LearningSolution"
Name="TheWindow">
<Window.Resources>
<ObjectDataProvider x:Key="EnumValues"
MethodName="GetValues"
ObjectType="{x:Type system:Enum}">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="local:LevelEnum" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
<DataTemplate x:Key="EnumValueTemplate">
<TextBlock Text="{Binding}"/>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ComboBox ItemsSource="{Binding Source={StaticResource EnumValues}}"
ItemTemplate="{StaticResource EnumValueTemplate}"
SelectedItem="{Binding ElementName=TheWindow, Path=TheLevel, Mode=OneWayToSource}"/>
<Button Click="Button_Click">Watch</Button>
</StackPanel>
</Window>
public partial class MainWindow : Window
{
public LevelEnum TheLevel { get; set; }
private void Button_Click(object sender, RoutedEventArgs e)
{
MessageBox.Show(this.TheLevel.ToString());
}
}
public enum LevelEnum { None = 0, First = 1, Second = 2, Third = 3 }
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:system="clr-namespace:System;assembly=mscorlib"
xmlns:local="clr-namespace:LearningSolution"
Name="TheWindow">
<Window.Resources>
<ObjectDataProvider x:Key="EnumValues"
MethodName="GetValues"
ObjectType="{x:Type system:Enum}">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="local:LevelEnum" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
<DataTemplate x:Key="EnumValueTemplate">
<TextBlock Text="{Binding}"/>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ComboBox ItemsSource="{Binding Source={StaticResource EnumValues}}"
ItemTemplate="{StaticResource EnumValueTemplate}"
SelectedItem="{Binding ElementName=TheWindow, Path=TheLevel, Mode=OneWayToSource}"/>
<Button Click="Button_Click">Watch</Button>
</StackPanel>
</Window>
public partial class MainWindow : Window
{
public LevelEnum TheLevel { get; set; }
private void Button_Click(object sender, RoutedEventArgs e)
{
MessageBox.Show(this.TheLevel.ToString());
}
}
public enum LevelEnum { None = 0, First = 1, Second = 2, Third = 3 }
For more information about binding and dependency property, you could refer to the following links.