Question

是否有一个简单的命令我可以使用Button发送到标准WPF ListBox，以便选择列表中的下一个/上一个项目？

目前我正在推出这个解决方案：

            <Button Width="30" Height="30" x:Name="PreviousButton">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="Click">
                        <ei:ChangePropertyAction Increment="True"
                                                 PropertyName="SelectedIndex"
                                                 TargetName="MyListBox"
                                                 Value="-1" />
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </Button>
           <!-- ListBox would be here. -->
           <Button Width="30" Height="30" x:Name="NextButton">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="Click">
                        <ei:ChangePropertyAction Increment="True"
                                                 PropertyName="SelectedIndex"
                                                 TargetName="MyListBox"
                                                 Value="1" />
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </Button>

哪个好。当你在列表中的第一个项目上时（如果与上一个项目相同），如果你点击上一个按钮会导致异常，但当前计划是告诉它如果selectedindex是第一个/最后一个项目，则禁用该按钮清单。

我问这个问题只是为了看看我是否比其他任何东西都错过了一个技巧。 “不，这是不可能的，你必须以其他方式这样做”，如果是这样的话，这是一个完全可以接受的答案。

Answer 1

没有＆＃34;标准＆＃34;命令，只需创建将改变int value;的NextItemCommand和PrevItemCommand，它可以绑定到ListBox.SelectedIndex，这就是你想要的。关于enable \ disable按钮只需为每个命令传递Enabled方法，以便检查value是否可以更改。

Answer 2

使用mvvm会更好，更简单。这就是我将如何解决它。请注意我的示例代码使用mvvmLight工具包。

查看

<Window x:Class="StackOverFlow1.MainWindow"
        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:StackOverFlow1"
        xmlns:viewModel="clr-namespace:StackOverFlow1.ViewModel"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <viewModel:MainViewModel x:Key="MainViewModel"/>
    </Window.Resources>
    <Grid DataContext="{StaticResource MainViewModel}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <ListBox Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" ItemsSource="{Binding Students}" x:Name="ListBox"
                 SelectedIndex="{Binding SelectedIndex}"/>
        <StackPanel Orientation="Horizontal" Grid.Row="1">
            <Button Content="Next" Width="50" Height="24" Command="{Binding NextCommand}" CommandParameter="{Binding ElementName=ListBox,Path=SelectedIndex}"/>
            <Button Content="Previous" Width="50" Height="24" Command="{Binding PreviousCommand}" CommandParameter="{Binding ElementName=ListBox,Path=SelectedIndex}"/>
        </StackPanel>
    </Grid>
</Window>

视图模型

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Windows.Input;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.CommandWpf;

namespace StackOverFlow1.ViewModel
{

    public class MainViewModel : ViewModelBase
    {

        public MainViewModel()
        {
         NextCommand=new RelayCommand<int>(OnNext,CanNext);
         PreviousCommand=new RelayCommand<int>(OnPrevious,CanPrevious);
            SelectedIndex = 0;

            foreach (var student in GetStudent())
            {
                _students.Add(student);
            }
        }

        public ICommand NextCommand { get; set; }
        public ICommand PreviousCommand { get; set; }
        private int _selectedIndex;


        private List<Student> GetStudent()
        {
            return new List<Student>()
            {
                new Student {Id = 0,Name = "Kwame0"},
                 new Student {Id = 0,Name = "Kwame1"},
                 new Student {Id = 0,Name = "Kwame2"},
                 new Student {Id = 0,Name = "Kwame3"},
                  new Student {Id = 0,Name = "Kwame4"},
                 new Student {Id = 0,Name = "Kwame5"},
                 new Student {Id = 0,Name = "Kwame6"},
                 new Student {Id = 0,Name = "Kwame7"},
                   new Student {Id = 0,Name = "Kwame8"},
                 new Student {Id = 0,Name = "Kwame9"},
                 new Student {Id = 0,Name = "Kwame10"},
                 new Student {Id = 0,Name = "Kwame11"},
                  new Student {Id = 0,Name = "Kwame12"},
                 new Student {Id = 0,Name = "Kwame13"},
                 new Student {Id = 0,Name = "Kwame14"},
                 new Student {Id = 0,Name = "Kwame15"},
            };
        }
        public int SelectedIndex
        {
            get { return _selectedIndex; }
            set { _selectedIndex = value;RaisePropertyChanged(()=>SelectedIndex); }
        }


        private ObservableCollection<Student> _students=new ObservableCollection<Student>();

        public ObservableCollection<Student> Students
        {
            get { return _students; }
            set { _students = value; }
        }


        private void OnNext(int index)
        {
            if (SelectedIndex != Students.Count)
                SelectedIndex += 1;
            else
            {
                SelectedIndex = 0;
            }
        }

        private bool CanNext(int indext)
        {
            return SelectedIndex != Students.Count;
        }

        private void OnPrevious(int index)
        {
            if (SelectedIndex != 0)
                SelectedIndex -= 1;
            else
            {
                SelectedIndex = Students.Count;
            }
        }

        private bool CanPrevious(int index)
        {
            return SelectedIndex != 0;
        }

    }

    public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return $"{Id}-{Name}";
        }
    }
}

按钮命令选择ListBox中的下一个/上一个项目

2 个答案: