Wpf gridcontrol cloumns disabled (DevExpress)

Question

I'm working in a wpf application, and i have a gridcontrol that contain a comboboxedit filled by a dataset table, but when i run it , the combobox items are shown but i can't select any of them(its like the combobox column is disabled).

so how can i make the items selectable ? thank's in advance 

 

     

<dxg:GridControl Name="grid" AutoGenerateColumns="AddNew" Margin="3,270,10,0" Grid.RowSpan="2" IsEnabled="True">

<dxg:GridControl.Columns>

<dxg:GridColumn Header="Code Materiel">

<dxg:GridColumn.EditSettings >

<dxe:ComboBoxEditSettings Name="cmbmat" IsEnabled="True" />

</dxg:GridColumn.EditSettings>

</dxg:GridColumn>

<dxg:GridColumn Header="Quantite" IsEnabled="True" UnboundType="Integer" AllowEditing="True">

<dxg:GridColumn.EditSettings>

<dxe:SpinEditSettings MinValue="1"/>

</dxg:GridColumn.EditSettings>

</dxg:GridColumn>

</dxg:GridControl.Columns>

<dxg:GridControl.View>

<dxg:TableView x:Name="view" NavigationStyle="Cell" NewItemRowPosition="Top" AllowEditing="True" />

</dxg:GridControl.View>

</dxg:GridControl>