C＃：按下Enter鍵時更改DropDownList值

Question

我有一個帶有固定數量項目的DropDownList的窗體窗體。當我按Enter鍵時，如何使DropDownList增量到下一個項目，當它到達項目的末尾時，返回到第一個項目。

Answer 1

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Text; 
using System.Windows.Forms; 

namespace WindowsFormsApplication1 
{ 
    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 
      this.KeyPreview = true; 
     } 

     private void Form1_Load(object sender, EventArgs e) 
     { 
      this.comboBox1.DataSource = CreateItems(); 

     } 


     private List<string> CreateItems() 
     { 
      List<string> lst = new List<string>(); 
      lst.Add("One"); 
      lst.Add("Two"); 
      lst.Add("Three"); 
      lst.Add("Four"); 
      return lst; 
     } 

     private void comboBox1_KeyDown(object sender, KeyEventArgs e) 
     { 
      if (e.KeyData == Keys.Enter) 
      { 
       if (comboBox1.SelectedIndex == comboBox1.Items.Count-1) 
       { 
        comboBox1.SelectedIndex = 0; 
        return; 
       } 

       if (comboBox1.SelectedIndex >=0 & comboBox1.SelectedIndex< comboBox1.Items.Count-1) 
       { 

        comboBox1.SelectedIndex = comboBox1.SelectedIndex+1; 
       } 

      } 
     } 

    } 
} 

Answer 2

您需要處理KeyDown事件並更改SelectedIndex屬性。