//自行补齐命名空间public static class Win32Utility {[DllImport("user32.dll", CharSet = CharSet.Auto)] private static extern Int32 SendMessage(IntPtr hWnd, int msg, int wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);[DllImport("user32.dll")] private static extern bool SendMessage(IntPtr hwnd, int msg, int wParam, StringBuilder lParam);[DllImport("user32.dll")] private static extern bool GetComboBoxInfo(IntPtr hwnd, ref COMBOBOXINFO pcbi);[StructLayout(LayoutKind.Sequential)] private struct COMBOBOXINFO { public int cbSize; public RECT rcItem; public RECT rcButton; public IntPtr stateButton; public IntPtr hwndCombo; public IntPtr hwndItem; public IntPtr hwndList; }[StructLayout(LayoutKind.Sequential)] private struct RECT { public int left; public int top; public int right; public int bottom; }private const int EM_SETCUEBANNER = 0x1501; private const int EM_GETCUEBANNER = 0x1502;public static void SetCueText(Control control, string text) { if (control is ComboBox) { COMBOBOXINFO info = GetComboBoxInfo(control); SendMessage(info.hwndItem, EM_SETCUEBANNER, 0, text); } else { SendMessage(control.Handle, EM_SETCUEBANNER, 0, text); } }private static COMBOBOXINFO GetComboBoxInfo(Control control) { COMBOBOXINFO info = new COMBOBOXINFO(); //a combobox is made up of three controls, a button, a list and textbox; //we want the textbox info.cbSize = Marshal.SizeOf(info); GetComboBoxInfo(control.Handle, ref info); return info; }public static string GetCueText(Control control) { StringBuilder builder = new StringBuilder(); if (control is ComboBox) { COMBOBOXINFO info = new COMBOBOXINFO(); //a combobox is made up of two controls, a list and textbox; //we want the textbox info.cbSize = Marshal.SizeOf(info); GetComboBoxInfo(control.Handle, ref info); SendMessage(info.hwndItem, EM_GETCUEBANNER, 0, builder); } else { SendMessage(control.Handle, EM_GETCUEBANNER, 0, builder); } return builder.ToString(); }}
首先建一个上面的类
需要引用别的命名空间
using System.Runtime.InteropServices;
using System.Windows.Forms;
使用时直接
Win32Utility.SetCueText(this.txtquery,"请输入");
