public void AddLeaveword(String sTitle,String sBody)
        {
       //定义数据库的Connection and Command 
         SqlConnection myConnection = new SqlConnection(SQLCONNECTIONSTRING);
         SqlCommand myCommand = new SqlCommand("Pr_AddLeaveword",myConnection);

      //定义访问数据库的方式为存储过程
          myCommand.CommandType = CommandType.StoredProcedure;

      //创建访问数据库的参数        
         SqlParameter parameterTitle = new SqlParameter("@title",SqlDbType.VarChar,30);
         parameterTitle.Value = sTitle;
         myCommand.Parameters.Add(parameterTitle);

        SqlParameter parameterBody = new SqlParameter("@messageContent",SqlDbType.VarChar,400);
         parameterBody.Value = sBody;
         myCommand.Parameters.Add(parameterBody);
             
             //SqlParameter parameterleaveName = new SqlParameter("@leaveName", SqlDbType.VarChar, 20);
            //parameterleaveName.Direction = ParameterDirection.ReturnValue;
            //myCommand.Parameters.Add(parameterleaveName);
            //SqlConnection conn = new SqlConnection("data source=(local);uid=sa;pwd=;database=data;pooling=true");
            这四句被我注释掉了，本来书上是这么给leaveName赋值的，可是这里我的leaveName为空。。因为同学的登陆界面还没做好
              不想编Session测试，想这先用插入看下可以不。。
            
            SqlConnection conn = new SqlConnection("data source=(local);uid=sa;pwd=;database=data;pooling=true");
            String strSQL = "insert into  leaveMessage(userID,leaveName)" + "values(admin , bluyzkl111)";
            SqlCommand comm = new SqlCommand(strSQL, conn);//插入userID和leaveName
        
            try
       {
        //打开数据库的连接
        myConnection.Open();
       }
       catch(Exception ex)
      {
            throw new Exception("数据库连接失败!",ex);
      }
           try 
     {
            //执行数据库的存储过程（访问数据库）
                   myCommand.ExecuteNonQuery();
     }
          catch(Exception ex)
         {
                throw new Exception(ex.Message,ex);
         }
      finally 
     {
            if (myConnection.State == ConnectionState.Open)
           {
         //关闭数据库的连接
          myConnection.Close();
           }
         }

          //return (char)parameterleaveName.Value;这句被我注释掉了，然后函数类型被我改成空的。。
           
}

SqlParameter parameterleaveName = new SqlParameter("@leaveName", SqlDbType.VarChar, 20);
parameterleaveName.Direction = ParameterDirection.ReturnValue;
parameterleaveName.Value="test"+DateTime.ToString("yyyyMMddhhmmss");
myCommand.Parameters.Add(parameterleaveName);

------解决方案--------------------
jf