WPF DataGrid 中的删除行按钮需要单击两次而不是一次

Question

我有一个 DataGrid，每行都有一个删除按钮，连接到删除命令。按钮需要点击两次才能删除行，这不是我想要的。

根据 Snoop 按钮的 IsEnabled == false 最初，第一次点击启用它。这似乎是问题所在，那么如何在用户点击之前启用按钮？

我试过用触发器改变IsEnabled，下面的代码中注释掉了，没用。

Window1.xaml

<Window x:Class="WpfApp1.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="Window1" Height="450" Width="800">
    <Grid>
        <DataGrid HorizontalAlignment="Left" Height="399" Margin="10,10,0,0" 
                  VerticalAlignment="Top" Width="772"
                  x:Name="dataGrid1" 
                  ItemsSource="{Binding ProxyServers}" 
                  CanUserAddRows="True" 
                  CanUserDeleteRows="True"
                  >
            <DataGrid.Columns>
                <DataGridTemplateColumn Width="SizeToCells">
                    <DataGridTemplateColumn.CellStyle>
                        <Style TargetType="{x:Type DataGridCell}" 
                            BasedOn="{StaticResource {x:Type DataGridCell}}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type DataGridCell}">

                                        <Button Command="DataGrid.DeleteCommand"  
                                            IsEnabled="True" x:Name="deleteButton" 
                                            Content="X">
                                           <!-- Make the button enable on mouse over?
                                                Didn't work.
                                                <Button.Style>
                                                <Style TargetType="Button">
                                                    <Style.Triggers>
                                                        <Trigger Property="IsMouseOver" 
                                                           Value="true">
                                                            <Setter Property="IsEnabled" 
                                                               Value="true" />
                                                        </Trigger>
                                                    </Style.Triggers>
                                                </Style>
                                            </Button.Style>-->
                                        </Button>

                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                            <Setter Property="IsEnabled" Value="True"/>

                        </Style>
                    </DataGridTemplateColumn.CellStyle>
                </DataGridTemplateColumn>

            </DataGrid.Columns>
        </DataGrid>

    </Grid>
</Window>

Window1.xaml.cs

using System.ComponentModel;
using System.Windows;


namespace WpfApp1
{

    public partial class Window1 : Window
    {
        BindingList<Proxy> proxyServers;

        public Window1()
        {
            InitializeComponent();
            dataGrid1.DataContext = this;

            proxyServers = new BindingList<Proxy>();
            proxyServers.Add(new Proxy() { LocalURL = "http://localhost" });
        }

        public BindingList<Proxy> ProxyServers { get => proxyServers; set => proxyServers = value; }
    }

    public class Proxy
    {
        string localURL;

        public string LocalURL { get => localURL; set => localURL = value; }
    }
}

Answer 1

你有没有考虑过类似的东西：

    <DataGridTemplateColumn Header="Delete">
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <Button Command="{Binding Deletecommand}"

如果你想在父视图的 daracontext 中使用命令，你可以使用 relativesource。使用 commandparameter 传递绑定的行对象。

Answer 2

详细说明@Andy 的回答。这是我必须做的。

添加 RelayCommand（这个实现在互联网上流传，我相信它来自 MVVMLite）：

using System;
using System.Windows.Input;

namespace WpfApp1
{

public class RelayCommand<T> : ICommand
{
    #region Fields

    readonly Action<T> _execute = null;
    readonly Predicate<T> _canExecute = null;

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of <see cref="DelegateCommand{T}"/>.
    /// </summary>
    /// <param name="execute">Delegate to execute when Execute is called on the command.  This can be null to just hook up a CanExecute delegate.</param>
    /// <remarks><seealso cref="CanExecute"/> will always return true.</remarks>
    public RelayCommand(Action<T> 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<T> execute, Predicate<T> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");

        _execute = execute;
        _canExecute = canExecute;
    }

    #endregion

    #region ICommand Members

    ///<summary>
    ///Defines the method that determines whether the command can execute in its current state.
    ///</summary>
    ///<param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
    ///<returns>
    ///true if this command can be executed; otherwise, false.
    ///</returns>
    public bool CanExecute(object parameter)
    {

        return _canExecute == null ? true : _canExecute((T)parameter);

    }

    ///<summary>
    ///Occurs when changes occur that affect whether or not the command should execute.
    ///</summary>
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    ///<summary>
    ///Defines the method to be called when the command is invoked.
    ///</summary>
    ///<param name="parameter">Data used by the command. If the command does not require data to be passed, this object can be set to <see langword="null" />.</param>
    public void Execute(object parameter)
    {
        _execute((T)parameter);
    }

    #endregion
}
}

定义我自己的 DeleteCommand 而不是使用 DataGrid 中的 build-in。我在 code-behind 中执行此操作，但在我的实际项目中，它在视图模型中进行。

private RelayCommand<object> _DeleteCommand;
public RelayCommand<object> DeleteCommand => _DeleteCommand ?? (_DeleteCommand = new RelayCommand<object>((object o) => {
    var proxy = o as Proxy;
    proxyServers.Remove(proxy);

}, (object o) => {
    if (o is Proxy)
    {
        return true;
    }
    else
    {
        return false;
    }
}));

我无法使用 RelayCommand<Proxy>，因为新项目行不是 Proxy 对象。如果我没有新项目行，我可以使用 RelayCommand<Proxy>.

删除 XAML 中的这个模板定义（因为它是 ControlTemplate 而不是 DataTemplate，看来你需要一个 DataTemplate 如果您想将网格项作为 CommandParameter)

传递给命令

                <DataGridTemplateColumn.CellStyle>
                    <Style TargetType="{x:Type DataGridCell}" BasedOn="{StaticResource {x:Type DataGridCell}}">
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate >

                                    <Button Command="{Binding DeleteCommand,RelativeSource={RelativeSource AncestorType={x:Type Window}}}" 
                                            CommandParameter="{Binding  RelativeSource={RelativeSource AncestorType={x:Type local:Proxy}}}"
                                            IsEnabled="True" x:Name="deleteButton" Content="X">

                                    </Button>

                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                        <Setter Property="IsEnabled" Value="True"/>

                    </Style>
                </DataGridTemplateColumn.CellStyle>

改为添加这个

        <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Button Command="{Binding DeleteCommand,RelativeSource={RelativeSource AncestorType={x:Type Window}}}" 
                                        CommandParameter="{Binding}"
                                        IsEnabled="True" x:Name="deleteButton" Content="X">

                    </Button>

                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>

WPF DataGrid 中的删除行按钮需要单击两次而不是一次

Delete row button in WPF DataGrid requires two clicks instead of one

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