//首先的引用下面三个文件

 //这几个文件的DLL在C:\Program Files\SAP\FrontEnd\SAPgui

  //具体需要看安装目录

 using SAPFunctionsOCX;

 using SAPLogonCtrl;

 using SAPTableFactoryCtrl;

   private void btnLogin_Click(object sender, EventArgs e)

         {

             //实例化一个SAPControl类的实例。

             SAPLogonCtrl.SAPLogonControlClass Login = new SAPLogonCtrl.SAPLogonControlClass();

             //指定连接SAP的各项参数。

             Login.User = this.txtUser.Text.Trim();

             Login.Password = this.txtUserPwd.Text.Trim();

             Login.Client = this.txtClient.Text.Trim();

             Login.Language = this.txtLanguage.Text.Trim().ToUpper();

             Login.ApplicationServer = this.txtIP.Text.Trim();

             Login.SystemNumber = Convert.ToInt32(this.txtSystemNumber.Text.Trim());

             //New一个连接对象去连接SAP

             SAPLogonCtrl.Connection Conn = (SAPLogonCtrl.Connection)Login.NewConnection();

             //调用Login方法检测是否可以正确登录。

             if (Conn.Logon(null, true))

             {

                 MessageBox.Show("连接SAP成功", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                 Conn.Logoff();

             }

             else

             {

                 MessageBox.Show("连接SAP失败", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);

             }

         }