Question

回答链接：（Can I put a horizontal line in a combo box or list control?）

我在C＃（VS 2010）Windows窗体中创建了一个代码，但它需要改进。项目前面的符号“ - ”会在项目后面显示一行。

我在组合项目集合中的输入如下：

-All Names
Henry (Father)
-Nancy (Mother)
Sapphire
Vincent

我的组合显示如下：

All Names
------------------
Henry (Father)
Nancy (Mother)
------------------
Sapphire
Vincent

我的代码是：

    public Form1()
    {
        InitializeComponent();
        comboBox1.DrawMode = DrawMode.OwnerDrawFixed;
        comboBox1.DrawItem += new DrawItemEventHandler(cmb_Type_DrawItem);
    }

    void cmb_Type_DrawItem(object sender, DrawItemEventArgs e)
    {
        e.DrawBackground();
        string a = comboBox1.Items[e.Index].ToString();
        if (comboBox1.Items[e.Index].ToString().Substring(0, 1) == "-")
        {
            e.Graphics.DrawLine(Pens.Black, new Point(e.Bounds.Left, e.Bounds.Bottom - 1),
            new Point(e.Bounds.Right, e.Bounds.Bottom - 1));
            a = a.Substring(1, a.Length - 1);
        }            
        TextRenderer.DrawText(e.Graphics, a,
        comboBox1.Font, e.Bounds, comboBox1.ForeColor, TextFormatFlags.Left);
        e.DrawFocusRectangle();
    }

我需要的改进是在“cmb_Type_DrawItem”中我想要“comboBox1”进行参数化，所以当我调用它时可以应用于任何调用它的comboBox（不仅仅是comboBox1）。

Answer 1

你可以像Blau建议的那样做，也可以创建一个将事件处理程序附加到组合框的函数。

void AttachHandler(ComboBox combo) {
    combo.DrawMode = DrawMode.OwnerDrawFixed;
    combo.DrawItem += new DrawItemEventHandler(cmb_Type_DrawItem);
}

然后，在表单构造函数中，您只需使用：

public Form1() {
    AttachHandler(comboBox1);
    AttachHandler(comboBox2);
}

Answer 2

使用Martin的解决方案加上公共变量。

    public Form1()
    {
        InitializeComponent();
        AttachHandler(comboBox1);
        AttachHandler(comboBox2);
        AttachHandler(comboBox3);
        AttachHandler(comboBox4);
        AttachHandler(comboBox5);
    }

    void AttachHandler(ComboBox combo)
    {
        combo.DrawMode = DrawMode.OwnerDrawFixed;
        combo.DrawItem += new DrawItemEventHandler(cmb_Type_DrawItem);
    }

    //using mycombo to make combobox variable
    void cmb_Type_DrawItem(object sender, DrawItemEventArgs e)
    {
        var mycombo = (ComboBox) sender;  // This is what I meant

        e.DrawBackground();
        string a = mycombo.Items[e.Index].ToString();
        if (mycombo.Items[e.Index].ToString().Substring(0, 1) == "-")
        {
            e.Graphics.DrawLine(Pens.Black, new Point(e.Bounds.Left, e.Bounds.Bottom - 1),
            new Point(e.Bounds.Right, e.Bounds.Bottom - 1));
            a = a.Substring(1, a.Length - 1);
        }
        TextRenderer.DrawText(e.Graphics, a, mycombo.Font, e.Bounds, mycombo.ForeColor, 
                     TextFormatFlags.Left);
        e.DrawFocusRectangle();
    }

Answer 3

创建自己的组合框：

  public class MyComboBox : ComboBox {

       override DrawItem() {
              ....
       }
  }

将水平线放在组合框中或列出C＃中的控件

3 个答案: