Question

我正在尝试一个例子。我在db中有一个名为Deleted的字段。。当我点击删除按钮实际上没有删除数据只是重复“N”与“Y”值问题是我下载源代码它工作但稍微改变后我得到这个例外。我想知道我做错了什么

此代码有效

         if (e.CommandName.Equals("Delete"))
         {

        long holidayNum = Convert.ToInt64(e.CommandArgument);




        using (SqlConnection con = new SqlConnection())
        {

            using (SqlCommand cmd = new SqlCommand())
            {

                cmd.Parameters.Add("@Deleted", SqlDbType.NChar).Value = "Y";

                cmd.CommandText = "Update HolidaysDetails set Deleted=@Deleted where HolidayNum=" + holidayNum;

                con.ConnectionString = connectionString;

                cmd.Connection = con;




                if (con.State == ConnectionState.Closed)
                {

                    con.Open();

                }

                int result = cmd.ExecuteNonQuery();

                con.Close();

                dlHoliday.EditItemIndex = -1;

                GetData();

            }

        }




    }

但我的代码抛出异常

      if (e.CommandName.Equals("delete"))
    {

        long holidayNum = Convert.ToInt64(e.CommandArgument);
         cmdText = "Update  HolidaysDetails set Deleted=@deleted where HolidayNum"  
         + holidayNum;
        using (con = new SqlConnection(cnnStr))
        {

            if (con.State == ConnectionState.Closed)
            {

                con.Open();
            }
            using (cmd = new SqlCommand())
            {

                cmd.Connection = con;
                cmd.CommandText = cmdText;
                cmd.Parameters.AddWithValue("@deleted", SqlDbType.NChar).Value = "Y";
                cmd.ExecuteNonQuery();
                con.Close();
                dlHoliday.EditItemIndex = -1;
                GetData();


            }
        }


    }

Answer 1

只是错过了这里的等号

cmdText = "Update  HolidaysDetails set Deleted=@deleted " + 
           "where HolidayNum=" + holidayNum;
                            ^

顺便说一句，当您尝试遵循正确的做法并使用@deleted标志的参数时，您做错了。作为第二个参数，AddWithValue要求值不是参数类型。修复它时，还要添加查询所需的第二个参数

cmdText = "Update  HolidaysDetails set Deleted=@deleted " + 
          "where HolidayNum=@num";
......
cmd.Connection = con;
cmd.CommandText = cmdText;
cmd.Parameters.AddWithValue("@deleted", "Y");
cmd.Parameters.AddWithValue("@num", holidaynum);
cmd.ExecuteNonQuery();
....

关于在期望条件的上下文中指定的非布尔类型的表达式的混淆

1 个答案: