如何添加 user32.dll 引用

怎么添加 user32.dll 引用
我已经把 user32.dll 复制到当前文件夹里了

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;
using System.Drawing.Printing;
using System.Drawing.Drawing2D;
using System.Runtime.InteropServices;

class AntiAlias : Form
{
    public static void Main()
    {
        Application.Run(new AntiAlias());
    }
    public AntiAlias()
    {
        Text = "Anti-Alias Demo";
        BackColor = SystemColors.Window;
        ForeColor = SystemColors.WindowText;
    }
   [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
       public int left;
       public int top;
       public int right;
       public int bottom;
    }
   [DllImport(user32.dll)]
   public static extern int ScrollWindow(IntPtr hwnd,int cx, int cy,
       ref RECT rectScroll,
       ref RECT rectClip);
}

错误 1 当前上下文中不存在名称“user32” C:\Users\hrao\Desktop\Project1\Project1\InheritHelloWorld.cs 29 15 Project1

------解决思路----------------------
http://www.cnblogs.com/goed/archive/2011/11/10/2243965.html
首先[DllImport(user32.dll)]是错误的应该是[DllImport("user32.dll")]
------解决思路----------------------
[DllImport("user32.dll")]