C#中使用SendMessage
在C#中使用SendMessage
日期:2005-02-04
作者:floodzhu
备注:主要描述在调用API函数SendMessage时数据类型的转换。
作者:floodzhu
备注:主要描述在调用API函数SendMessage时数据类型的转换。
SendMessage是一个在user32.dll中声明的API函数,在C#中导入如下:
using System.Runtime.InteropServices;
[DllImport("user32.dll", EntryPoint="SendMessageA")] public static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);
本文描述其参数 lParam 的用法,主要是数据类型之间的转化。
● 一种最简单的处理方式是声明多个SendMessage函数(overload),用所需的数据类型直接替换IntPtr。例如:
//声明: [DllImport("user32.dll", EntryPoint="SendMessageA")] private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, string lParam); [DllImport("user32.dll", EntryPoint="SendMessageA")] private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, ref Rectangle lParam);
//调用: string s = "hello, floodzhu"; SendMessage(this.textBox1.Handle, WM_SETTEXT, IntPtr.Zero, s); Rectangle rect = new Rectangle(); SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, ref rect);
● 对要求返回字符串的类型(out string)可以用 StringBuilder 代替,此时不需要 out/ref。例如:
[DllImport("user32.dll", EntryPoint="SendMessageA")] private static extern int SendMessage (IntPtr hwnd, int wMsg, int wParam, StringBuilder lParam); private void button1_Click(object sender, System.EventArgs e) { const int buffer_size = 1024; StringBuilder buffer = new StringBuilder(buffer_size); SendMessage(this.textBox1.Handle, WM_GETTEXT, buffer_size, buffer); //MessageBox.Show(buffer.ToString()); }
● 如果想用 InPtr 类型统一处理的话,可以借助于 Marshal 或者 GCHandle 的相关方法。例如:
[DllImport("user32.dll", EntryPoint="SendMessageA")] private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam); private void button2_Click(object sender, System.EventArgs e) { Rectangle rect = new Rectangle(); IntPtr buffer = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Rectangle))); Marshal.StructureToPtr(rect, buffer ,true); SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, buffer); rect = (Rectangle)Marshal.PtrToStructure(buffer, typeof(Rectangle)); Marshal.FreeHGlobal(buffer); }
或者
private void button2_Click(object sender, System.EventArgs e) { Rectangle rect = new Rectangle(); GCHandle gch = GCHandle.Alloc(rect); SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, (IntPtr)gch); rect = (Rectangle)Marshal.PtrToStructure((IntPtr)gch, typeof(Rectangle)); gch.Free(); }
转载:https://www.cnblogs.com/me-sa/articles/669402.html
本文来自博客园,作者:.net&new,转载请注明原文链接:https://www.cnblogs.com/wugh8726254/p/15982626.html