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WPF Command绑定并传参(以DataGrid示例)

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); } }

 

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