C#調用Windows API函數,實現透明表單 – 轉

這篇文章不是Windows Mobile的，而是Win32的。這篇文章主要介紹一下C#下如何調用Windows API函數，這裡也想說一下，Windows Mobile編程不能把眼光只局限於手機，手機與PC端相結合的程式也是很有挑戰力、很有市場的。所以，這也是我寫這篇文章的原因之一。

        做Delphi的時候，實現表單透明很簡單，因為Delphi對Windows API的封裝很好。不只對API函數封裝的到位，對API函數所用到的參數封裝的也很好。而.net沒有對API函數進行封裝，對API函數的參數就更沒有封裝了。調用API函數只能用Invoke的方式，參數也需要我們自己進行相關定義。

DesktopWinAPI.cs類檔案，Invoke了表單透明所需要的API函數：

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單元是API函數的調用方式：

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);
        }
    }
}