如何强制只有当用户单击下拉按钮时才能打开DropDownList样式的组合框?

在其他答案的帮助下,我得出了以下快速解决方案:

public class MyComboBox : ComboBox
{
    public MyComboBox()
    {
        FlatStyle = FlatStyle.Popup;
        DropDownStyle = ComboBoxStyle.DropDownList;
    }

    protected override void WndProc(ref Message m)
    {
        if (m.Msg == 0x0201 /* WM_LBUTTONDOWN */ || m.Msg == 0x0203 /* WM_LBUTTONDBLCLK */)
        {
            int x = m.LParam.ToInt32() & 0xFFFF;
            if (x >= Width - SystemInformation.VerticalScrollBarWidth)
                base.WndProc(ref m);
            else
            {
                Focus();
                Invalidate();
            }
        }
        else
            base.WndProc(ref m);
    }
}

    void comboBox1_MouseClick(object sender, MouseEventArgs e)
    {
        ComboBox combo = sender as ComboBox;
        int left = combo.Width - (SystemInformation.HorizontalScrollBarThumbWidth + SystemInformation.HorizontalResizeBorderThickness);
        if (e.X >= left)
        {
            // They did click the button, so let it happen.
        }
        else
        {
            // They didn't click the button, so prevent the dropdown.
        }
    }

comboBox1.DropDownStyle = ComboBoxStyle.DropDown;

但是,这允许在框中键入您可能不需要的内容。

public class CustomComboBox : ComboBox
{
    protected override void OnMouseClick(MouseEventArgs e)
    {
        base.OnMouseClick(e);

        int left = this.Width - (SystemInformation.HorizontalScrollBarThumbWidth + SystemInformation.HorizontalResizeBorderThickness);
        if (e.X >= left)
        {
            // They did click the button, so let it happen.
            base.OnMouseClick(e);
        }
        else
        {
            // They didn't click the button, so prevent the dropdown.
            // Just do nothing.
        }
    }
}

你可以得到鼠标点击的X,Y位置,如果它不在下拉“图标”上(因为没有更好的词),你可以从那里强制它折叠。