//新建一个类，引用DLL，继承DLL接口函数
//有指针的话，指针用IntPtr定义，结构体ref BookInfo info-重新定义DLL中结构体
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

public class Device
{
    /// <summary>
    ///初始化接口
    ///参数说明：无
    ///返回值：成功返回0，错误返回-1
    /// </summary>
    /// <returns></returns>
    [DllImport(@"TuShu.dll")]
    public static extern int Init();

    /// <summary>
    /// Book   /// </summary>
    /// <param name=""></param>
    [DllImport(@"TuShu.dll")]
    public static extern int Book(Guid guid, IntPtr BookType, int BookNo);
}

        //form.cs中可这样写

        /// <summary>
        /// 初始化
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                //初始化
                int Ret = Device.Init();
                if (Ret == 0)
                {
                    MessageBox.Show("初始化成功！");
                }
                else
                {
                    //失败
                    MessageBox.Show("初始化失败：" + Ret.ToString());
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("初始化异常：" + ex.Message);
            }
        }