Issue binding SelectedItem of Combobox with in Datagrid-WPF

I have WPF application created in .net framework 3.5 which uses MVVM pattern. I have a wpftoolkit Datagrid which has a column which consists of combobox with in the datatemplate. My datagrid is binded to a data table present in the ViewModel.

 

I need to bind the SelectedItem property of the combobox present in Datagrid to one of the column present in Datatable. Basically I also have textblock and textbox with in the datagrid, but this controls get properly binded to datatable columns.

 

Following is the Xaml code snippet :

 

TextBox Binding(Working properly ) :

 

<toolkit:DataGridTemplateColumn.CellTemplate>

                                <DataTemplate >

                                    <TextBox BorderThickness="0" Text="{Binding TxtbindedColumn}" />   

                                   

                                </DataTemplate>

</toolkit:DataGridTemplateColumn.CellTemplate>

 

 

ComboBox binding :

 

<ComboBox x:Name="Cmb1"

                                  AutomationProperties.AutomationId="Cmb1" AutomationProperties.Name="Cmb1"

                                  ItemsSource="{Binding DataContext.ComboEntity,RelativeSource={RelativeSource AncestorType={x:Type        wpfwiz:WizardResultPageBase}}}"

                                  DisplayMemberPath="Desc"     

                                  SelectedValuePath="Id"

                                  TabIndex="3"

                                  Foreground="Black"

                                  IsSynchronizedWithCurrentItem="False"

                                  SelectedItem="{Binding CmbbindedColumn}">

</ComboBox>

 

Datatable in Viewmodel :

 

  public DataTable PagedGridList

        {

            get

            {

                return _pagedGridList;

            }

            set

            {

                _pagedGridList = value;

                if (_pagedGridList != null)

                {

                    _pagedGridList.Columns[0].ColumnName = " TxtbindedColumn ";

                    _pagedGridList.Columns[1].ColumnName = " CmbbindedColumn ";

}

     }

}

 

 

 

Need a urgent help on this.