How to create columns dynamic in datagrid in mvvm application

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C#3.5

MVVM

hi,
i want to bind the DataGrid in MVVM with dynamica create column. i don't know how to Implement please help. i have taken many reference form google search but not any works.

below are the my tried code please help.
i am using vs 2012.


thanks in advance.

What I have tried:

in xaml file code:
<datagrid x:name="DataGridUsers" xmlns:x="#unknown">
ItemsSource="{Binding Users}"
attachedBehaviors:DataGridColumnsBehavior.BindableColumns="{Binding UserRoleColumns}"
AutoGenerateColumns="False"
EnableRowVirtualization="False"/>

viewModel file code:

private void GenerateDefaultColumns()
{
this.UserRoleColumns.Add(
new DataGridTextColumn { Header = "First Name", Binding = new Binding("FirstName") });
this.UserRoleColumns.Add(new DataGridTextColumn { Header = "Last Name", Binding = new Binding("LastName") });
}
public ObservableCollection<datagridcolumn> UserRoleColumns { get; private set; }