public class ViewModelFactory
{
 private static Dictionary<string, object> vmMap = new Dictionary<string, object>();<br>
 public static T GetViewModel<T>() where T : ViewModelBase
 {
  Type vmType = typeof(T);
  if (vmMap.ContainsKey(vmType.FullName))
  {
   return (T)vmMap[vmType.FullName];
  }
  else
  {
   object vm = Activator.CreateInstance(vmType);
   vmMap.Add(vmType.FullName, vm);
   return (T)vm;
  }
 }

 public static T GetViewModel<T>(object[] data,string id) where T : ViewModelBase
 {
  Type vmType = typeof(T);
  if (vmMap.ContainsKey(id))
  {
   return (T)vmMap[id];
  }
  else
  {
   object vm = Activator.CreateInstance(vmType, data);
   vmMap.Add(id, vm);
   return (T)vm;
  }
 }
}

public delegate void CloseEventHandle(object sender);
 public class CustomViewModel : ViewModelBase
 {

  public event CloseEventHandle CloseEvent;
 protected bool hasData;

  public CustomViewModel()
  {
  LoadCommand = new RelayCommand(() =>
   {
    if (!hasData)
    {

     ThreadPool.QueueUserWorkItem((obj) =>
     {
      lock (this)
      {
       OnLoad();
       hasData = true;
      }
     });
    }
   });
  }public RelayCommand LoadCommand { private set; get; }

  protected virtual void OnLoad()
  {

  }

  protected void OnClose(object sender)
  {
   if (sender != null && CloseEvent != null)
   {
    CloseEvent(sender);
   }
  }
 }

public class ShowHelper
 {
  private static Dictionary<string, Window> windowManager = new Dictionary<string, Window>();

  public static void ShowDiaglogUc<T>(string title, object[] constructors = null, bool isDialog = false) where T : UserControl
  {
   Type controlType = typeof(T);
   string key;

   if (constructors == null) //如果构造参数为null
   {
    key = controlType.FullName; //key = T 的完全限定名
   }
   else
   {
    // 如果不为空 并且 第二个构造参数为string（第二个参数代表id -->有可能是GroupId 有可能是UserId）；
    if (constructors.Length == 2 && constructors[1] is string) //ps：这里本人写死了可以根据需求自行修改
    {
     key = controlType.FullName + constructors[1].ToString(); //key = 控件 完全限定名+id;
    }
    else //不满足条件
    {
     key = controlType.FullName; //key = 限定名
    }

   }

   if (windowManager.ContainsKey(key)) //如果包含KEY
   {
    windowManager[key].Topmost = true; //设置TopMost
    return;
   }

   UserControl content;
   if (constructors == null)
   {
    content = Activator.CreateInstance(controlType) as UserControl;
   }
   else
   {
    content = Activator.CreateInstance(controlType, constructors) as UserControl;
   }

   BaseWindow window = new BaseWindow(); //PS这是自己封装 的Window，（可以用直接用原始的Wpf Widnow）
   window.Title = title;
   windowManager.Add(key, window);
   window.Closed += (sen, cloE) =>
   {
    windowManager.Remove(key);
   };
   if (isDialog)
   {
    window.ShowDialog();
   }
   else
   {
    window.Show();
   }
   #region 注册关闭事件
   if (content.DataContext as CustomViewModel != null)
   {
    CustomViewModel vm = content.DataContext as CustomViewModel;
    vm.CloseEvent += (obj) =>
    {
     if (content.DataContext.Equals(obj))
     {
      window.Close();
     }
    };
   }
   #endregion
  }


  public static CustomDialogResult ShowOkCancleUC<T>(string title, MsgBoxBtn okCancle, out object data) where T : Control
  {
   Type vmType = typeof(T);
   Control content = Activator.CreateInstance(vmType) as Control;
   OkCanleWindow window = new OkCanleWindow();
   window.ShowInTaskbar = false;
   return window.ShowDialog(title, okCancle, content, out data);
  }

  public static CustomDialogResult MessageBoxDialog(string title, string message, MsgBoxBtn okCancle)
  {
   OkCanleWindow window = new OkCanleWindow();
   window.ShowInTaskbar = false;
   object none;
   return window.ShowDialog(title, okCancle, new MessageUC() { Message = message }, out none);
  }


、（1）开始剖析 public static void ShowDiaglogUc<T>(string title, object[] constructors = null, bool isDialog = false) where T : UserControl
　　ShowDialogUc 是用来在VM中用来创建UserControl并显示在Window中的。你可能会问为啥用windowManager 将窗口缓存起来（PS这里主要还是为了解决单例窗口的麻烦），

　　至于 下面这段代码，我们可以回到创建的CustomerViewModel中，对这里需要注册VM中CloseEvent事件，这样我们在VM中就可以直接调用OnClose（）方法就OK了

　　#region 注册关闭事件
   if (content.DataContext as CustomViewModel != null)
   {
    CustomViewModel vm = content.DataContext as CustomViewModel;
    vm.CloseEvent += (obj) =>
    {
     if (content.DataContext.Equals(obj))
     {
      window.Close();
     }
    };
   }
　　#region 注册关闭事件

<controls:BaseWindow x:Class="Common.OkCanleWindow"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:controls="clr-namespace:Controls;assembly=Controls"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="MessageBoxWindow">
 <Grid x:Name="grid">
  <Grid.RowDefinitions>
   <RowDefinition/>
   <RowDefinition Height="50"/>
  </Grid.RowDefinitions>
  <Grid.ColumnDefinitions>
   <ColumnDefinition/>
   <ColumnDefinition/>
  </Grid.ColumnDefinitions>
  <Button Content="确 定" x:Name="okBtn" Click="okBtn_Click" Grid.Row="1" Height="30" Width="120" HorizontalAlignment="Right" Margin="0 0 10 0"/>
  <Button Content="取 消" x:Name="canleBtn" Click="canleBtn_Click" Grid.Row="1" Grid.Column="1" Height="30" Width="120" HorizontalAlignment="Left" Margin="10 0 0 0"/>

 </Grid>
</controls:BaseWindow>

  后台代码：

public partial class OkCanleWindow : BaseWindow
 {
  public OkCanleWindow()
  {
   InitializeComponent();
this.Closed += (s, e) =>
    {
     if (result == CustomDialogResult.None)
     {
      result = CustomDialogResult.Cancel;
     }

    };
  }
  private System.Windows.Controls.Control control;

  CustomDialogResult result;
  public CustomDialogResult ShowDialog(string title, MsgBoxBtn btnState, Control uc, out object dataContext)
  {
   #region 设置控件
   if (btnState == MsgBoxBtn.Ok) //如果为OK状态
   {
    Grid.SetColumnSpan(okBtn, 2); //设置OK按钮跨两列
    okBtn.HorizontalAlignment = System.Windows.HorizontalAlignment.Center; //设置OK按钮居中对齐
    canleBtn.Visibility = System.Windows.Visibility.Collapsed; //设置Cancel 按钮隐藏;
    if (uc != null)
    {
     control = uc;  
     Grid.SetRow(uc, 0); //设置控件所在Grid 的行
     Grid.SetColumnSpan(uc, 2); //设置控件所在Grid 的列
     this.Width = uc.Width; //设置窗体宽度
     this.Height = uc.Height + grid.RowDefinitions[1].Height.Value + 35; //设置窗体宽度 高度
     grid.Children.Add(uc); //加入控件
    }
   }
   if (btnState == MsgBoxBtn.None) //如果为None 既没有OK 也没有 Cancle
   {
    grid.RowDefinitions.RemoveAt(1);
    okBtn.Visibility = System.Windows.Visibility.Collapsed;
    canleBtn.Visibility = System.Windows.Visibility.Hidden;
    if(uc !=null)
    {
     control = uc;
     Grid.SetRow(uc, 0); //设置控件所在Grid 的行
     Grid.SetColumnSpan(uc, 2); //设置控件所在Grid 的列
     this.Width = uc.Width; //设置窗体宽度
     this.Height = uc.Height + 35;
     grid.Children.Add(uc); //加入控件
    }
   }
   
   this.Title = title;
   dataContext = uc.DataContext;
   #endregion
   this.ShowDialog();return result;
  }

  private void okBtn_Click(object sender, RoutedEventArgs e)
  {
   result = CustomDialogResult.OK;
   this.Close();
  }

  private void canleBtn_Click(object sender, RoutedEventArgs e)
  {
   result = CustomDialogResult.Cancel;
   this.Close();
  }
 }

 public enum CustomDialogResult 
 {
  None,OK,Cancel
 }

 public enum MsgBoxBtn 
 {
  None,Ok,OkCancel
 }