我的代码如下:
     public partial class Form1 : Form
    {
        [DllImport("LOTcontroller.dll")]
        private static extern HANDLE OpenPort(int port,int baud);
        [DllImport("LOTcontroller.dll")]
        private static extern BOOL ClosePort(HANDLE m_hComm);
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            HANDLE a = OpenPort(2,9600);
            bool b = CloseReason(a);
            if (b == true)
            {
                MessageBox.Show("已经关闭!");
            }
        }
    }

在运行的时候提示:缺少Using 指令或程序集

引用那加using System.Runtime.InteropServices;

请问我的Dll应该放到什么位置呢?

我加了:using System.Runtime.InteropServices;
还是不行啊.
还是缺少Using 指令或程序集啊

bool b = CloseReason(a);
改成 bool b = ClosePort(a);

它老是提示缺少"HANDLE "程序集啊.

把HANDLE类型改为IntPtr试试,在C#IntPtr代表句柄类型