<DataGridTemplateColumn Header="Доктор"  >
      <DataGridTemplateColumn.CellTemplate>
         <DataTemplate>
            <TextBlock  Text="{Binding DoctorId, Converter={local:DoctorNumberConverter}}"/>                     
         </DataTemplate>
      </DataGridTemplateColumn.CellTemplate>
      <DataGridTemplateColumn.CellEditingTemplate>
           <DataTemplate>
                 <ComboBox ItemsSource="{Binding DataDoctorsWithDatails, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}}"
                                                                          SelectedValue="{Binding Path=DoctorId, UpdateSourceTrigger=PropertyChanged}"
                                                                          SelectedValuePath="IdDoctor" 
                                                                          DisplayMemberPath="NameDoctor" 
                                                                          IsEditable="True"  >
                      <ComboBox.ItemTemplate>
                           <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                     <TextBlock  Width="300" Text="{Binding NameDoctor}" />
                                     <TextBlock Width="270" Text="{Binding CommentsDoctor}" />
                                     <TextBlock Width="270" Text="{Binding NameDoctorGroup}"  />
                                     <TextBlock Text="{Binding NameFirm}" Width="600"/>
                                </StackPanel>
                          </DataTemplate>
                      </ComboBox.ItemTemplate>
                  </ComboBox>
               </DataTemplate>
           </DataGridTemplateColumn.CellEditingTemplate>
       </DataGridTemplateColumn>

<TextBlock  Text="{Binding DoctorId, Converter={local:DoctorNumberConverter}}"/>