Source code/ View: http://stackoverflow.com/questions/20400257/remove-the-item-which-is-selected-in-other-combobox-from-source

gistfile1.xml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <StackPanel>
            <ComboBox x:Name="ComboBox1"  ItemsSource="{Binding SourceCollection1}" DisplayMemberPath="Name" SelectedItem="{Binding Selected1}"/>
            <ComboBox x:Name="ComboBox2" ItemsSource="{Binding SourceCollection2}" DisplayMemberPath="Name" SelectedItem="{Binding Selected2}"/>
            <ComboBox x:Name="ComboBox3"  ItemsSource="{Binding SourceCollection3}" DisplayMemberPath="Name" SelectedItem="{Binding Selected3}"/>
            <ComboBox x:Name="ComboBox4" ItemsSource="{Binding SourceCollection4}" DisplayMemberPath="Name" SelectedItem="{Binding Selected4}"/>
        </StackPanel>
    </Grid>
</Window>