How to implement correct resizing in DataGrid?

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C#

WPF

Hi!

XAML:

<datagrid>
       ...
       extensions:DataGridExtension.DataContextForColumns="{Binding Mode=OneWay}"
       >

C#:

public class DataGridExtension
{
    static DataGridExtension()
    {
        try
	{
	    //Allows to set DataContextProperty on the columns. Must only be invoked once per application.
	    FrameworkElement.DataContextProperty.AddOwner(typeof (DataGridColumn));
	}
	catch
	{
	}
    }

    public static object GetDataContextForColumns(DependencyObject obj)
    {
        return obj.GetValue(DataContextForColumnsProperty);
    }
	 
    public static void SetDataContextForColumns(DependencyObject obj, object value)
    {
        obj.SetValue(DataContextForColumnsProperty, value);
    }
 
    /// <summary>
    /// Allows to set DataContext property on columns of the DataGrid (DataGridColumn)
    /// </summary>
    /// <example><datagridtextcolumn header="{Binding DataContext.ColumnHeader, RelativeSource= {RelativeSource Self}}" /></example>
    public static readonly DependencyProperty DataContextForColumnsProperty =
                DependencyProperty.RegisterAttached(
	        "DataContextForColumns",
	        typeof(object),
	        typeof(DataGridExtension),
	        new UIPropertyMetadata(OnDataContextChanged));
	 
    /// <summary>
    /// Propogates the context change to all the DataGrid's columns
    /// </summary>
    private static void OnDataContextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var grid = d as DataGrid;
        if (grid == null) return;
	 
        foreach (DataGridColumn col in grid.Columns)
            col.SetValue(FrameworkElement.DataContextProperty, e.NewValue);
    }
}

Resizing by double-clicking on a split line in the header works correct without extensions:DataGridExtension.DataContextForColumns attribute for DataGrid: affects only columns located on the right(it works in such way by default). With this attribute resizing affects columns located on the left. I don't understand this dependency and how to make deal with it. I need both correct resizing and setting the data context for the grid.