如何将占位符文本添加到 ToolStripTextBox？

Question

在 WinForms 项目中，我知道如何将 placeholder text 添加到常规文本框。但 ToolStripTextBox 似乎不是常规文本框。一方面，它不公开句柄（这是通过 Win API 设置占位符文本所需要的）。

那么，如何在 ToolStripTextBox 上设置占位符文本或获取其 .Handle 属性？

Answer 1

自己没试过。

但是 Remarks 部分表明您可以直接操作 TextBox 控件。

ToolStripTextBox is the TextBox optimized for hosting in a ToolStrip. A subset of the hosted control's properties and events are exposed at the ToolStripTextBox level, but the underlying TextBox control is fully accessible through the TextBox property.

Answer 2

ToolStripTextBox 主持 ToolStripTextBoxControl inside which is derived from TextBox and you can access the the hosted control using its TextBox or its Control 属性。所以你可以写这样的代码：

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

[ToolboxBitmap(typeof(ToolStripTextBox))]
public class MyToolStripTextBox : ToolStripTextBox
{
    private const int EM_SETCUEBANNER = 0x1501;
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern Int32 SendMessage(IntPtr hWnd, int msg,
        int wParam, string lParam);
    public MyToolStripTextBox()
    {
        this.Control.HandleCreated += Control_HandleCreated;
    }
    private void Control_HandleCreated(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(cueBanner))
            UpdateCueBanner();
    }
    string cueBanner;
    public string CueBanner
    {
        get { return cueBanner; }
        set
        {
            cueBanner = value;
            UpdateCueBanner();
        }
    }
    private void UpdateCueBanner()
    {
        SendMessage(this.Control.Handle, EM_SETCUEBANNER, 0, cueBanner);
    }
}

如何将占位符文本添加到 ToolStripTextBox？

How to add placeholder text to ToolStripTextBox?

.net

c#

toolstrip

winforms