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如何统一/简化此代码-事件处理/委派?

delegates refactoring .net c#

Cade Roux · 技术社区 · 15 年前

我有从两个不同视图监视的流程对象。Windows.Forms.ListView(实际上是派生类)和图形查看器(基于Microsoft Research的自动图形布局)。每个都有一个上下文菜单,可以激活类似的事件。虽然列表视图可以有多个选择,但我不允许在图表视图中使用它。

这是我目前拥有的:

    private void ctxgrphAddBreakpoint_Click(object sender, EventArgs e)
    {
        Process p = GetProcess(viewer);
        if (p != null)
        {
            p.AddBreakpoint();
            BeginRefresh(false, false);
        }
    }

    private void ctxgrphRemoveBreakpoint_Click(object sender, EventArgs e)
    {
        Process p = GetProcess(viewer);
        if (p != null)
        {
            p.RemoveBreakpoint();
            BeginRefresh(false, false);
        }
    }

    private void ctxlistAddBreakpoint_Click(object sender, EventArgs e)
    {
        foreach (Process p in lvwProcessList.SelectedProcesses())
        {
            p.AddBreakpoint();
        }
        BeginRefresh(false, false);
    }

    private void ctxlistRemoveBreakpoint_Click(object sender, EventArgs e)
    {
        foreach (Process p in lvwProcessList.SelectedProcesses())
        {
            p.RemoveBreakpoint();
        }
        BeginRefresh(false, false);
    }

我想将两个上下文菜单统一为一个,并将事件处理统一为一个,如下所示:

    private void ctxlistAction_Click(object sender, EventArgs e)
    {
        // I can unify the Viewer and ListView and implement some common interface,
        // so I'm pretty sure I can handle this part
        foreach (Process p in UIView.SelectedProcesses())
        {
            p.Action(); // What is the best way to handle this?
        }
        BeginRefresh(false, false);
    }

我怎么去那儿?

4 回复 | 直到 15 年前

Kelly S. French 15 年前

访客模式?

Nestor 15 年前

定位事件分配( ... += new System.EventHandler(ctxlistAction_Click); )在*.designer.cs文件中,使它们指向相同的函数。

mdm20 15 年前

你不能把发送者强制转换到你的接口上吗?

 private void ctxlistAction_Click(object sender, EventArgs e)
 {
      UIView view = sender as UIView;

      if (view != null)
      {

         // I can unify the Viewer and ListView and implement some common interface,
         // so I'm pretty sure I can handle this part
         foreach (Process p in view.SelectedProcesses())
         {
             p.Action(); // What is the best way to handle this?
         }
         BeginRefresh(false, false);
      }
  }

dan 15 年前

首先,尝试重构公共功能并使用委托 (请原谅我对“Dolistaction”这样的名字选择不当):

readonly Action<Process> removeBreakpoint = p => p.RemoveBreakpoint();
readonly Action<Process> addBreakpoint = p => p.AddBreakpoint(); 

void DoSingleAction(Action<Process> action)
{
     var p = GetProcess(viewer);
     if(p != null)
     {
         action(p); //invokes the action
         BeginRefresh(null,null);
     }
}

void DoListAction(Action<Process> action)
{
    lvwProcessList.ForEach(action);
    BeginRefresh(false, false);
}



private void ctxgrphAddBreakpoint_Click(object sender, EventArgs e)
{
    DoSingleAction(addBreakpoint);
}

private void ctxgrphRemoveBreakpoint_Click(object sender, EventArgs e)
{
    DoSingleAction(removeBreakpoint);
}

private void ctxlistAddBreakpoint_Click(object sender, EventArgs e)
{
    DoListAction(addBreakpoint);
}

private void ctxlistRemoveBreakpoint_Click(object sender, EventArgs e)
{
    DoListAction(removeBreakpoint);
}

然后可以统一doProcessAction和dolisaction:

void DoAction(object sender, Action<Process>)
{
     if(sender is ListView)
     {
         lvwProcessList.ForEach(action);
         BeginRefresh(false, false);
     }
     else if (sender is GraphView)
     {
         var p = GetProcess(viewer);
         if(p != null)
         {
             action(p); //invokes the action
             BeginRefresh(null,null);
         }
     }
     else {throw new Exception("sender is not ListView or GraphView");}
}

//and update all the handlers to use this, and delete DoSingleAction and DoListAction:
private void ctxgrphAddBreakpoint_Click(object sender, EventArgs e)
{
    DoAction(sender, addBreakpoint);
}
//etc.

不管怎样,在每个事件处理程序中,我认为您必须指定要采取的操作。在这种情况下,我不确定继承或扩展方法是否真的是您的朋友,但下面是使用扩展方法的情况:

//these two are in a separate static class
public static InvokeAction(this ListView listView, Action<Process> action)
{ ... }
public static InvokeAction(this GraphView listView, Action<Process> action)
{ ... }

private void handler(object sender, Action<Process> action)
{ 
    var lv = sender as ListView;
    var gv = sender as GraphVeiw;    
    lv.InvokeAction(action); //(need to check for null first)
    gv.InvokeAction(action);
    if(lv == null && gv == null) {throw new Exception("sender is not ListView or GraphView");}
}

//then update all the handlers:
private void ctxgrphAddBreakpoint_Click(object sender, EventArgs e)
{
    handler(sender, addBreakpoint);
}

C 2/.NET 2

要在C 2(VS2005)中实现这一点,使用委托的第一种方法仍然有效,您不能使用lambda。(2.0具有 Action<T> 代表)。只需将lambda更改为函数即可。其他一切都会正常工作。

void removeBreakpoint(Process p) { p.RemoveBreakpoint(); }
void addBreakpoint(Process p) { p.AddBreakpoint(); }

//you could also do this, but it's overkill:
readonly Action<Process> removeBreakpoint = delegate(Process p) { p.RemoveBreakpoint(); };
readonly Action<Process> addBreakpoint = delegate(Process p) { p.AddBreakpoint(); };