基于WPF系统框架设计(9)-多值绑定之IMultiValueConverter

应用场景

我想把View层的一个布局控件和功能按钮传到ViewModel层，达到动态变更布局，同时灵活获取功能按钮的属性，让View和ViewModel完全分离，而不受View层影响。

最后我想到使用IMultiValueConverter实现多参传入ViewModel层来解决，不知道还有没有更好的办法？

基本原理：要将值转换器与 MultiBinding 关联，请创建一个实现 IMultiValueConverter 接口的类，然后实现 Convert 和 ConvertBack 方法。
集合中的各个绑定可以具有自己的值转换器。

使用 MultiBinding，您可以将绑定目标属性绑定到源属性列表，然后应用逻辑以使用给定的输入生成值。

实现步骤

    添加继承IMultiValueConverter接口的类并实现接口

    注意:返回的values一定要转为数组列表values.ToArray()

参考如下代码

using System;

using System.Linq;

using System.Net;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Ink;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Animation;

using System.Windows.Shapes;



namespace TLAgent.SecurityManager.WPF.MultiBindings

{

  public class DataConverter : IMultiValueConverter

  {

    #region IMultiValueConverter Members



    public object Convert(object[] values, Type targetType,

      object parameter, System.Globalization.CultureInfo culture)

    {

        return values.ToArray() ;

    }



    public object[] ConvertBack(object value, Type[] targetTypes,

      object parameter, System.Globalization.CultureInfo culture)

    {

        throw new NotImplementedException();

    }



    #endregion

  }

}

在XAML中进行多参绑定

<Fluent:Button Header="添加用户" Icon="Images\Green.png" LargeIcon="Images\GreenLarge.png" x:Name="BtnAddUser" Command="{Binding AddUserCommand}">

                        <Fluent:Button.CommandParameter>

                            <MultiBinding Converter="{ StaticResource ResourceKey=dataConverter}" Mode="TwoWay">

                                <MultiBinding.Bindings>

                                    <Binding ElementName="BtnAddUser"/>

                                    <Binding ElementName="dockManager "/>

                                </MultiBinding.Bindings>

                            </MultiBinding>

                        </Fluent:Button.CommandParameter>

                        

                    </Fluent:Button>

<Window.Resources>

        <local:DataConverter x:Key="dataConverter"/>

</Window.Resources>

ViewModel中进行命令和方法绑定

注意：DelegateCommand<object[]>的参数是要支持对象数组。

using System;

using System.Linq;

using System.Reflection;

using System.Windows;

using System.Windows.Input;

using Microsoft.Practices.Prism.Commands;

using Microsoft.Practices.Prism.ViewModel;

using Xceed.Wpf.AvalonDock;

using Xceed.Wpf.AvalonDock.Layout;

using Application = System.Windows.Application;

using MessageBox = System.Windows.MessageBox;

using UserControl = System.Windows.Controls.UserControl;



namespace TLAgent.SecurityManager.WPF.ViewModels

{

    public class MainWindowViewModel : NotificationObject

    {

        public ICommand ExitSystemCommand { get; set; }



        public ICommand AddUserCommand { get; set; }



        public ICommand OpenHelpCommand { get; set; }



        public MainWindowViewModel()

        {

            ExitSystemCommand = new DelegateCommand(this.OnExit);

            OpenHelpCommand = new DelegateCommand(this.OnOpenSupport);

            AddUserCommand = new DelegateCommand<object[]>(this.AddUser);

        }





        private void CreateTab(DockingManager dockManager, string tabName, UserControl control)

        {

            var firstDocumentPane = dockManager.Layout.Descendents().OfType<LayoutDocumentPane>().FirstOrDefault();

            if (firstDocumentPane != null)

            {

                LayoutDocument doc2 = new LayoutDocument();

                doc2.Title = tabName;

                doc2.Content = control;

                doc2.IsActive = true;

                firstDocumentPane.Children.Add(doc2);

            }

        }



        private void OnExit()

        {

            MessageBoxResult result = MessageBox.Show("确定要退出系统吗?", "确认消息", MessageBoxButton.OKCancel, MessageBoxImage.Question);

            if (result == MessageBoxResult.OK)

            {

                Application.Current.Shutdown();

            }

        }



        private void OnOpenSupport()

        {

            MessageBox.Show("帮助窗口!");

        }

        

       private void AddUser(object[] objParam)

       {

            if (objParam.Length == 2)

            {

                Fluent.Button button = (Fluent.Button)objParam[0];

                DockingManager dockingManager = (DockingManager)objParam[1];

                UserControl control;

                control = new UserControl1();



                CreateTab(dockingManager, button.Header.ToString(), control);

            }

      }

    }

}

控件绑定

这样就可以在方法AddUer的参数中取得View层绑定的两个控件:

<MultiBinding.Bindings>

     <Binding ElementName="BtnAddUser"/>

     <Binding ElementName="dockManager "/>

</MultiBinding.Bindings>

这样基本就实现了从View层传多个对象到ViewModel层了。