How to get Data Grid column index on right click? MVVM WPF

Question

I want to get column Index and pass it by CommandParameter I have, in a context menu for Data grid column header.

<DataGrid.Resources>
     <ContextMenu x:Key="DataGridColumnHeaderContextMenu">
           <MenuItem Header="Freez Column"
                     Command="{Binding DataContext.FreezColumnCommand, RelativeSource={RelativeSource AncestorType=DataGrid}}"
                     CommandParameter="{Binding}" />
     </ContextMenu>
     <Style TargetType="{x:Type DataGridColumnHeader}">
           <Setter Property="ContextMenu" Value="{StaticResource DataGridColumnHeaderContextMenu}" />
     </Style>
</DataGrid.Resources>

I've tried to pass the entire object by passing Binding in CommandParameter, but it only passes the header text.

And tried using RelateveSource AncestorType=DataGridColumn still couldn't figure it out.

Edit:

DataGrid code:

<DataGrid ItemsSource="{Binding MyList}" HorizontalScrollBarVisibility="Visible" CanUserAddRows="False" AutoGenerateColumns="False">
     <DataGrid.Resources>
          <ContextMenu x:Key="DataGridColumnHeaderContextMenu">
               <MenuItem Header="Freez Column"
                         Command="{Binding DataContext.FreezColumnCommand, RelativeSource={RelativeSource AncestorType=DataGrid}}"
                         CommandParameter="{Binding}" />
          </ContextMenu>
          <Style TargetType="{x:Type DataGridColumnHeader}">
                <Setter Property="ContextMenu" Value="{StaticResource DataGridColumnHeaderContextMenu}" />
          </Style>
     </DataGrid.Resources>
     <DataGrid.Columns>
          <DataGridTextColumn Header="Story" Binding="{Binding Story}" />
          <DataGridCheckBoxColumn Header="Design" Binding="{Binding Design}" />
          <DataGridTextColumn Header="CadId" Binding="{Binding CadId}" />
     </DataGrid.Columns>
</DataGrid>

Answer 1

This is happening probably because of ContextMenu is maintained in separate VisualTree(correct me if i'm wrong). Please use the below code to get DisplayIndex,

  <DataGrid
        x:Name="myGrid"
        AutoGenerateColumns="False"
        CanUserAddRows="False"
        HorizontalScrollBarVisibility="Visible"
        ItemsSource="{Binding Persons}">
        <DataGrid.Resources>
            <local:GridToIndexConverter x:Key="GridToIndexConverter" />
            <ContextMenu x:Key="DataGridColumnHeaderContextMenu">
                <MenuItem
                    Command="{Binding DataContext.FreezColumnCommand, RelativeSource={RelativeSource AncestorType=DataGrid}}"
                    CommandParameter="{Binding PlacementTarget.DisplayIndex, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ContextMenu}}"
                    Header="Freez Column" />
            </ContextMenu>
            <Style TargetType="{x:Type DataGridColumnHeader}">
                <Setter Property="ContextMenu" Value="{StaticResource DataGridColumnHeaderContextMenu}" />
            </Style>
        </DataGrid.Resources>
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding Story}" Header="Story" />
            <DataGridCheckBoxColumn Binding="{Binding Design}" Header="Design" />
            <DataGridTextColumn Binding="{Binding CadId}" Header="CadId" />
        </DataGrid.Columns>
    </DataGrid>

i have accessed PlacementTarget of ContextMenu.