<UserControl.Resources>
        <local:StatusConvertor x:Key="StatusConvertor"></local:StatusConvertor>
        <cvt:FullNameConverter x:Key="fullNameConverter"></cvt:FullNameConverter>
        
        <DataTemplate x:Key="doctorTemplate">
            <TextBlock Text="{Binding .,Converter={StaticResource ResourceKey=fullNameConverter}}" Margin="4,0,0,0"></TextBlock>
        </DataTemplate>
        
    </UserControl.Resources>

<dxe:ComboBoxEdit Name="comboBoxEdit_Doctor"
                  ApplyItemTemplateToSelectedItem="True"
                  ItemTemplate="{StaticResource ResourceKey=doctorTemplate}" 
                  IsTextEditable="False" ShowCustomItems="True" 
                  Margin="0,1"  Width="300" HorizontalAlignment="Left" 
                 SelectedIndexChanged="comboBoxEdit_Doctor_SelectedIndexChanged" />