- A+
所属分类：.NET技术
一、问题场景：
使用WPF的DataGrid来展示表格数据，想要批量删除或者导出数据行时，由于SelectedItems属性不支持MVVM的方式绑定（该属性是只读属性），所以可以通过命令参数的方式将该属性值传给命令，即利用CommandParameter将SelectedItems传递给删除或导出命令。
二、使用方式：
1.xaml部分
<DataGrid x:Name="dtgResult" ItemsSource="{Binding ResultInfo}" CanUserSortColumns="True" Height="205" Width="866" AutoGenerateColumns="False"> <DataGrid.Columns> <DataGridTextColumn Header="患者ID" Binding="{Binding PatientId}" MinWidth="46" IsReadOnly="True"/> <DataGridTextColumn Header="姓名" Binding="{Binding PatientName}" MinWidth="46" IsReadOnly="True"/> <DataGridTextColumn Header="性别" Binding="{Binding PatientGender}" MinWidth="46" IsReadOnly="True"/> </DataGrid.Columns> </DataGrid>
<Button x:Name="btnResultDel" Content="删除" Command="{Binding ResultDeleteCommand}" CommandParameter="{Binding SelectedItems,ElementName=dtgResult}"/>
2.C#部分
private RelayCommand _deleteCommand;
public ICommand ResultDeleteCommand {
get
{
if (_deleteCommand == null) {
_deleteCommand = new RelayCommand(param =>On_Delete_Command_Excuted(param)); } return _deleteCommand; } } private void On_Delete_Command_Excuted(Object param) {
}
每次触发ResultDeleteCommand，都会把控件dtgResult的SelectedItems属性值作为参数param传递给On_Delete_Command_Excuted方法。
三、Tip
1.如何把Object类型的参数转成List<T>呢？ （其中T是DataGrid中每条数据的类型）
System.Collections.IList items = (System.Collections.IList)param; var collection = items.Cast<T>(); var selectedItems = collection.ToList();
其中selectedItems就是用户在DataGrid界面选中的多条数据行。
2.RelayCommand
/// <summary> /// A command whose sole purpose is to relay its functionality to other objects by invoking delegates. The default return value for the CanExecute method is 'true'. /// </summary> public class RelayCommand : ICommand { readonly Action<object> _execute; readonly Predicate<object> _canExecute; /// <summary> /// Creates a new command that can always execute. /// </summary> /// <param name="execute">The execution logic.</param> public RelayCommand(Action<object> execute): this(execute, null) { } /// <summary> /// Creates a new command. /// </summary> /// <param name="execute">The execution logic.</param> /// <param name="canExecute">The execution status logic.</param> public RelayCommand(Action<object> execute, Predicate<object> canExecute) { if (execute == null) throw new ArgumentNullException("execute");
_execute = execute; _canExecute = canExecute; } public bool CanExecute(object parameter) { return _canExecute == null ? true : _canExecute(parameter); } public event EventHandler CanExecuteChanged { add { CommandManager.RequerySuggested += value; } remove { CommandManager.RequerySuggested -= value; } } public void Execute(object parameter) { _execute(parameter); } }
