如何将字符串属性值设置为 Datagrid 内的 ComboBox 控件？

Question

I have a DataGrid in my WPF project. The model which I am binding has property DataType of type string . In normal display mode I am displaying it like:

<DataGridTemplateColumn.CellTemplate>
   <DataTemplate>
      <TextBlock Style="{StaticResource CellBlock}" Text="{Binding DataType}" ToolTip="{Binding DataType}"/>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

In edit mode I need to populate an enum in the ComboBox and set the selected combo box item to the item which is coming from string model property Datatype and if user changes the value in combobox it should get reflected in model. How can I achieve these things?

Answer 1

You do not need a custom cell template for that, DataGrid has a built-in DataGridComboBoxColumn . In normal mode, it displays the value as text and in edit-mode it shows a ComboBox .

You have to expose the constants that your enum defines as a collection. You can create a simple MarkupExtension for that that returns the values of any given enum type.

public class EnumValuesExtension : MarkupExtension
{
   public Type Type { get; set; }

   public override object ProvideValue(IServiceProvider serviceProvider)
   {
      return Enum.GetValues(typeof(MyEnum));
   }
}

This is an example of your DataGrid . As you can see, you can simply use the markup extension to bind the ItemsSource of the combo box column to your enum type, which is MyEnum here.

<DataGrid ItemsSource="{Binding newItems}">
   <DataGrid.Columns>
      <DataGridComboBoxColumn ItemsSource="{local:EnumValues Type={x:Type local:MyEnum}}"
                              SelectedItemBinding="{Binding DataType}"/>
   </DataGrid.Columns>
</DataGrid>

In your model, use the enum type for the DataType property. I do not think there is any use in exposing it as string . The example above assumes that you use your enum type, not string .

However, if you really depend on it being a string , you can create a simple value converter .

public class StringToEnumConverter : IValueConverter
{
   public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
   {
      return Enum.Parse((Type)parameter, (string)value);
   }

   public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
   {
      return value.ToString();
   }
}

This would change the binding on the combo box column to this:

<DataGridComboBoxColumn ItemsSource="{local:EnumValues Type={x:Type local:MyEnum}}"
                        SelectedItemBinding="{Binding DataType, Converter={StaticResource StringToEnumConverter}, ConverterParameter={x:Type local:MyEnum}}"/>