Question

我正在研究.net c＃，我想在表格中插入一些数据。

我在Visual Studio中编写查询而不使用存储过程。

这是我的查询

SqlCommand cmd2 = new SqlCommand("insert into Device_Events (Device_ID, Event_ID, Occurrence_Time, Recovery_Time) values (@Device_ID , @Event_ID, @Occurrence_Time, @Recovery_Time)", con);

这是我在其中传递值的C＃代码

// For Events
string formatString = "yyMMddHHmmss";
DateTime Occurrence_Time, Recovery_Time;
string strOccurrence = Meter_data.Substring(161, 12);
string strRecovery = Meter_data.Substring(173, 12);

cmd2.Parameters.AddWithValue("@Device_ID", device_Id);
cmd2.Parameters.AddWithValue("@Event_ID", event_Id);

if (DateTime.TryParseExact(strOccurrence, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Occurrence_Time))
{
    if (DateTime.TryParseExact(strRecovery, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Recovery_Time))
    {
        cmd2.Parameters.AddWithValue("@Occurrence_Time", SqlDbType.DateTime).Value = Occurrence_Time;
        cmd2.Parameters.AddWithValue("@Recovery_Time", SqlDbType.DateTime).Value = Recovery_Time;
    }
}

int Device_Events_rows_executed = cmd2.ExecuteNonQuery();
Console.WriteLine("Rows Executed: '{0}'", Device_Events_rows_executed);

它没有进入if部分，我得到一个名为Must declare the scalar variable "@Occurrence_Time"

的异常

此外，我已阅读此link但无法找到任何帮助

更新代码

在提出建议后，我添加了以下代码

            cmd2.Parameters.Add("@Device_ID", SqlDbType.VarChar, 50).Value = device_Id;
            cmd2.Parameters.Add("@Event_ID", SqlDbType.VarChar, 50).Value = event_Id;
            cmd2.Parameters.Add("@Occurrence_Time", SqlDbType.DateTime, 50).Value = DBNull.Value;
            cmd2.Parameters.Add("@Recovery_Time", SqlDbType.DateTime, 50).Value = DBNull.Value;

            string formatString = "yyMMddHHmmss";
            DateTime Occurrence_Time, Recovery_Time;
            string strOccurrence = Meter_data.Substring(161, 12);
            string strRecovery = Meter_data.Substring(173, 12);

            if (DateTime.TryParseExact(strOccurrence, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Occurrence_Time))
            {
                cmd2.Parameters["@Occurrence_Time"].Value = Occurrence_Time;
            }
            if (DateTime.TryParseExact(strRecovery, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Recovery_Time))
            {
                cmd2.Parameters["@Recovery_Time"].Value = Recovery_Time;
            }

虽然它没有显示我和错误或异常，但它仍未进入if条件

任何帮助都将受到高度赞赏

Answer 1

您始终需要声明所有参数，但如果缺少日期，您可以传递null或默认值：

if (DateTime.TryParseExact(strOccurrence, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Occurrence_Time))
{               
    cmd2.Parameters.AddWithValue("@Occurrence_Time", SqlDbType.DateTime).Value = Occurrence_Time;                
}
else 
{
    cmd2.Parameters.AddWithValue("@Occurrence_Time", SqlDbType.DateTime).Value = null;
}

Answer 2

如上所述，由于您的条件流，有一些代码路径，您可以尝试执行cmd2而无需在命令中添加参数。

必须将参数添加到命令中，即使它们没有值。我建议您在开始时设置所有参数（使用Add()而不是AddWithValue()）：

cmd2.Parameters.Add("@Device_ID", SqlDbType.VarChar, 50).Value = device_Id;
cmd2.Parameters.Add("@Event_ID", SqlDbType.VarChar, 50).Value = event_Id;
cmd2.Parameters.Add("@Occurrence_Time", SqlDbType.DateTime, 50).Value = DBNull.Value;
cmd2.Parameters.Add("@Recovery_Time", SqlDbType.DateTime, 50).Value = DBNull.Value;

然后，如果您的字符串正确解析为日期，请更新参数的值：

if (DateTime.TryParseExact(strOccurrence, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Occurrence_Time))
{
    cmd2.Parameters["@Occurrence_Time"].Value = Occurrence_Time;
}
if (DateTime.TryParseExact(strRecovery, formatString, CultureInfo.InvariantCulture, DateTimeStyles.None, out Recovery_Time))
{
    cmd2.Parameters["@Recovery_Time"].Value = Recovery_Time;
}

修改

您似乎非常确信数据始终是正确的，因此您也可以使用ParseExact代替TryParseExact：

var occuranceDate = DateTime.ParseExact(Meter_data.Substring(161, 12), "yyMMddHHmmss", CultureInfo.InvariantCulture); var recoveryDate = DateTime.ParseExact(Meter_data.Substring(173, 12), "yyMMddHHmmss", CultureInfo.InvariantCulture); cmd2.Parameters.Add("@Device_ID", SqlDbType.VarChar, 50).Value = device_Id; cmd2.Parameters.Add("@Event_ID", SqlDbType.VarChar, 50).Value = event_Id; cmd2.Parameters.Add("@Occurrence_Time", SqlDbType.DateTime, 50).Value = occuranceDate' cmd2.Parameters.Add("@Recovery_Time", SqlDbType.DateTime, 50).Value = recoveryDate; int Device_Events_rows_executed = cmd2.ExecuteNonQuery(); Console.WriteLine("Rows Executed: '{0}'", Device_Events_rows_executed);

C＃必须在插入查询中声明标量变量“@SomeThing”

2 个答案: