C#调用Windows API函数,实现透明窗体 转

这篇文章不是Windows Mobile的，而是Win32的。这篇文章主要介绍一下C#下如何调用Windows API函数，这里也想说一下，Windows Mobile编程不能把眼光只局限于手机，手机与PC端相结合的程序也是很有挑战力、很有市场的。所以，这也是我写这篇文章的原因之一。

        做Delphi的时候，实现窗体透明很简单，因为Delphi对Windows API的封装很好。不只对API函数封装的到位，对API函数所用到的参数封装的也很好。而.net没有对API函数进行封装，对API函数的参数就更没有封装了。调用API函数只能用Invoke的方式，参数也需要我们自己进行相关定义。

DesktopWinAPI.cs类文件，Invoke了窗体透明所需要的API函数：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace DeviceAnywhereDesktop
{
    class DesktopWinAPI
    {
        [DllImport("user32.dll")]
        public extern static IntPtr GetDesktopWindow();

        [DllImport("user32.dll")]
        public extern static bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey, byte bAlpha, uint dwFlags);
        public static uint  LWA_COLORKEY = 0x00000001;
        public static uint LWA_ALPHA = 0x00000002;

        [DllImport("user32.dll")]
        public extern static uint SetWindowLong(IntPtr hwnd, int nIndex, uint dwNewLong);
        [DllImport("user32.dll")]
        public extern static uint GetWindowLong(IntPtr hwnd, int nIndex);

        public enum WindowStyle : int
        {
            GWL_EXSTYLE = -20
        }

        public enum ExWindowStyle : uint
        {
            WS_EX_LAYERED = 0x00080000
        }

    }
}

DeviceForm.cs单元是API函数的调用方式：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace DeviceAnywhereDesktop
{
    public partial class DeviceForm : Form
    {
        public DeviceForm()
        {
            InitializeComponent();
        }

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams cp = base.CreateParams;

                cp.Parent = DesktopWinAPI.GetDesktopWindow();
                cp.ExStyle = 0x00000080 | 0x00000008;//WS_EX_TOOLWINDOW | WS_EX_TOPMOST

                return cp;
            }
        }

        private void SetWindowTransparent(byte bAlpha)
        {
            try
            {
                DesktopWinAPI.SetWindowLong(this.Handle, (int)DesktopWinAPI.WindowStyle.GWL_EXSTYLE,
                    DesktopWinAPI.GetWindowLong(this.Handle, (int)DesktopWinAPI.WindowStyle.GWL_EXSTYLE) | (uint)DesktopWinAPI.ExWindowStyle.WS_EX_LAYERED);

                DesktopWinAPI.SetLayeredWindowAttributes(this.Handle, 0, bAlpha, DesktopWinAPI.LWA_COLORKEY | DesktopWinAPI.LWA_ALPHA);
            }
            catch
            {
            }
        }
       

        private void DeviceForm_Load(object sender, EventArgs e)
        {
            this.SetWindowTransparent(100);
        }
    }
}