最简单的方法来监视组合框值之间的变化

Question

我正在寻找一个优雅的方式来跟踪值组合框之间的变化。我期望做的是在SelectionChanged事件发生时触发自定义事件，但仅限于特定的值更改。这意味着要知道初始值是什么。只有当初始值从z改变时，该事件才会被触发。如果初始值为a，b或c，则该事件不会被触发。但如果初始值是z，它将被触发。

有没有人有一个优雅的方式来解决这个问题？

Answer 1

为此，您需要创建一个自定义事件处理程序，并且可以自定义事件参数，

//Event Handler Class 
public class SpecialIndexMonitor 
{ 
     public event EventHandler<SpecialIndexEventArgs> SpecialIndexSelected; 
     //Custom Function to handle Special Index 
     public void ProcessRequest(object sender, System.EventArgs e) 
     { 
      //Your custom logic 
      //Your code goes here 
      //Raise event 
      if(SpecialIndexSelected != null) 
      { 
       SpecialIndexEventArgs args = new SpecialIndexEventArgs{ 
        SelectedIndex = ((ComboBox) sender).SelectedIndex; 
       }; 
       SpecialIndexSelected(this, args); 
      } 
     } 
} 

//Custom Event Args 
public class SpecialIndexEventArgs : EventArgs 
{ 
    //Custom Properties 
    public int SelectedIndex { get; set; } //For Example 
    //Default Constructor 
    public SpecialIndexEventArgs() 
    { 
    } 
} 

内，您的形式

//Hold previous value 
private string _previousItem; 

//IMPORTANT: 
//After binding items to combo box you will need to assign, 
//default selected item to '_previousItem', 
//which will make sure SelectedIndexChanged works all the time 

// Usage of Custom Event 
private void comboBox1_SelectedIndexChanged(object sender, 
    System.EventArgs e) 
{ 
     string selectedItem = (string)comboBox1.SelectedItem; 
     if(string.Equals(_previousItem,) 
     switch(_previousItem) 
     { 
      case "z": 
      { 
       SpecialIndexMonitor spIndMonitor = new SpecialIndexMonitor(); 
       spIndMonitor.SpecialIndexSelected += 
        new EventHandler<SpecialIndexEventArgs>(SpecialIndexSelected); 
       break; 
      } 
      case "a": 
      case "b": 
       break; 
     } 
     _previousItem = selectedItem; //Re-Assign the current item 
} 
void SpecialIndexSelected(object sender, SpecialIndexEventArgs args) 
{ 
    // Your code goes here to handle the special index 
} 

有没有编译的代码，但在逻辑上它应该为你工作。