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I'm creating a DataGrid which has a DataGridTemplateColumn with a custom ComboBox. I want to change the ItemSource of this ComboBox according to a value selected in a previous column. To achieve this I'm using a IMultiValueConverter, I noticed when I change the ItemSource of the second row the selected value on the first row gets set to blank when the selected item is no available anymore in that ItemSource. Below the code is an image for a clearer explanation

In xaml

<shell:ShellDataGrid x:Name="parameterDataGrid" ItemsSource="{Binding SelectedMethod.Parameters}" AutoGenerateColumns="false" CanUserAddRows="false" 

                    IsSynchronizedWithCurrentItem="True" HeadersVisibility="Column" SelectionMode="Single" SelectionUnit="FullRow">

    <shell:ShellDataGrid.Columns>

        <shell:DataGridTemplateColumn Header="DataType" IsReadOnly="False">

            <shell:DataGridTemplateColumn.CellTemplate>

                <DataTemplate>

                    <shell:ShellComboBox ItemsSource="{Binding  ElementName=parameterDataGrid, Path=DataContext.DataTypes}"

                                         SelectedItem="{Binding DataType, UpdateSourceTrigger=PropertyChanged}" >

                    </shell:ShellComboBox>

                </DataTemplate>

            </shell:DataGridTemplateColumn.CellTemplate>

        </shell:DataGridTemplateColumn>

        <shell:DataGridTemplateColumn Header="Usage" IsReadOnly="False">

            <shell:DataGridTemplateColumn.CellTemplate>

                <DataTemplate>

                    <shell:ShellComboBox

                                 SelectedItem="{Binding Usage, UpdateSourceTrigger=PropertyChanged}" >

                        <shell:ShellComboBox.ItemsSource>

                            <MultiBinding Converter="{StaticResource ParameterUsageConverter}">

                                <MultiBinding.Bindings>

                                    <Binding ElementName="parameterDataGrid" Path="DataContext.TerminalUsageEnumList"/>

                                    <Binding ElementName="parameterDataGrid" Path="SelectedItem"/>

                                </MultiBinding.Bindings>

                            </MultiBinding>

                        </shell:ShellComboBox.ItemsSource>

                    </shell:ShellComboBox>

                </DataTemplate>

            </shell:DataGridTemplateColumn.CellTemplate>

        </shell:DataGridTemplateColumn>

        <shell:DataGridDeleteColumn/>

    </shell:ShellDataGrid.Columns>

</shell:ShellDataGrid>

My ParameterUsageConverter

public class ParameterUsageConverter : IMultiValueConverter

{

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

    {

        var usages = (values[0] as ObservableCollection<ParameterCallUsage>).ToObservableCollection();

        var methodParameter = values[1] as ParameterPlaceHolder;



        if (!methodParameter.DataType.IsClassOrInterface())

            usages.Remove(ParameterCallUsage.DynamicDispatch);



        return usages;

    }



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

    {

        throw new NotImplementedException();

    }

}

As shown in the image, the upper DataGrid shows with DynamicDispatch still in the ItemSource List, in the lower one, a row is selected which datatype is not a class so the DynamicDispatch item gets removed from the ItemSource, so the first row immediately response to that by displaying nothing in the Usage Column
Here is the image of how my DataGrid looks

So, how do I make the XAML that my ItemSource is independent for every row?