data not visible in wpf combo box of data grid

Hi,I am having one problem related to ComboBox of DataGrid. Data is binding but it is not visible in the ComboBox after binding. My code is like below.

<my:DataGridTemplateColumnHeader="UsgSrc"><my:DataGridTemplateColumn.CellTemplate><DataTemplate><ComboBoxName="cbUsgSrc"ItemsSource="{Binding Source={StaticResource UsgSrcUOMS}}"SelectedValue="{Binding Path=UsgSrc}"SelectedValuePath="UtType"DisplayMemberPath="UtType"></ComboBox></DataTemplate></my:DataGridTemplateColumn.CellTemplate></my:DataGridTemplateColumn>
In the code behind I am assigning data like below.
ObjectDataProvider UsageSrcUOMS = null;
UsageSrcUOMS = (ObjectDataProvider)FindResource("UsgSrcUOMS");
UsageSrcUOMS.ObjectInstance = objUtView;
Microsoft.Windows.Controls.DataGridCell cell = obj.GetCell(dgMtrHdr, J, 11);
if (cell != null)
{
ContentPresenter panel = cell.Content as ContentPresenter;
if (panel != null)
{
ComboBox cmbUsUtilit = obj.GetVisualChild<ComboBox>(panel);
cmbUsUtilit.IsEnabled = true;
if(objUtView!=null) cmbUsUtilit.ItemsSource = objUtView;
cmbUsUtilit.SelectedIndex=2;
}
}
After binding in the combo box, selected index item is selecting. But data is not visible.
Please help me to solve my problem.

cas