Question

我在下面的这行给了我标题错误。

dtDetail = SQLQuery.getRequestDetails(reqNo, vendorcode);

但我测试了它，dtDetail不为空，reqNo不为空，vendorCode不为空，我不在乎。

logger.Debug("request#: " + reqNo);
logger.Debug("vendor code: " + vendorcode);
System.Data.DataTable dtDetail = new System.Data.DataTable();
if (dtDetail == null)
    logger.Debug("dtDetail is null.");
if (SQLQuery.getRequestDetails(reqNo, vendorcode) == null)
    logger.Debug("SQLQuery.getRequestDetails(reqNo, vendorcode) is null.");
dtDetail = SQLQuery.getRequestDetails(reqNo, vendorcode);

我使用来自SQLQuery.getRequestDetails(reqNo, vendorcode)的{{1}}和reqNo来测试vendorCode，其中没有例外。

所有测试均在我的本地PC上完成，但连接到生产数据库。 Windows 7 Pro Service Pack 1。

给我错误的是生产环境，Windows XP Pro 2002 Service Pack 3。

下面是SQLQuery类。

logger.Debug

我甚至去写了一个新函数，但它在生产环境中也给了我同样的错误。

public static class SQLQuery
{
    private static ILog logger = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    public static DataTable getRequestDetails(string reqNo, string vendorcode)
    {
        DataSet ds = new DataSet();
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT * FROM vw_drawing_req_status WHERE  regno = '" + reqNo + "'" + " AND vendorcode = '" + vendorcode + "'";

            ds = myDB.GetDataSet(strSQL);
        }
        catch (Exception ex)
        {
            logger.Error("request#: " + reqNo + ", vendor code: " + vendorcode, ex);
            throw ex;
        }
        finally
        {

        }
        if (ds.Tables[0].Rows.Count > 0)
            return ds.Tables[0];
        else
            return null;
    }

    public static DataTable getRFQDetail(string reqNo, string vendorcode)
    {
        DataSet ds;
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT * FROM t_RFQ_info WHERE  regno = '" + reqNo + "'" +
                "AND vendor_code = '" + vendorcode + "'";

            ds = myDB.GetDataSet(strSQL);
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }
        if (ds.Tables[0].Rows.Count > 0)
            return ds.Tables[0];
        else
            return null;
    }

    public static DataTable getVendorEmailAddress(string comp_code, string vendorcode)
    {
        DataSet ds;
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT * FROM t_vendor_email WHERE  comp_code = '" + comp_code + "'" +
                "AND vendor = '" + vendorcode + "' AND status = 1";

            ds = myDB.GetDataSet(strSQL);
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }

        return ds.Tables[0];

    }

    public static string getModuleNumber(string reqNo)
    {
        DataSet ds;
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT moduleno FROM subconjobQ WHERE  regno = '" + reqNo + "'";

            ret = myDB.GetOneValue(strSQL).ToString();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }
        return ret;
    }

    public static string getPlant(string reqNo)
    {
        DataSet ds;
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT plant FROM subconjobQ WHERE  regno = '" + reqNo + "'";

            ret = myDB.GetOneValue(strSQL).ToString();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }
        return ret;
    }

    public static string getVendorCurrency(string plant, string vendorcode)
    {
        DataSet ds;
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " SELECT currency FROM t_vendor_info WHERE  plant = '" + plant + "'" +
                "AND vendor = '" + vendorcode + "' AND status = 1";

            ret = myDB.GetOneValue(strSQL).ToString();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }
        return ret;
    }

    public static void updateRFQTable(string regno, string vendor, string partno, string currency, double procCost, double rawCost, double treatCost, double unitPrice, string leadTime)
    {
        string strSQL = string.Empty;
        ATSSPCommon.SQLDB myDB = null;
        string ret = string.Empty;
        try
        {
            string strConnectionString = Config.DrawingConnString();
            myDB = new ATSSPCommon.SQLDB(strConnectionString);

            strSQL = " UPDATE t_RFQ_info SET " +
                "currency = '" + currency + "', " +
                "process_cost = " + procCost + ", " +
                "rawmat_cost = " + rawCost + ", " +
                "treatment_cost = " + treatCost + ", " +
                "unit_price = " + unitPrice + ", " +
                "lead_time = '" + leadTime.Trim() + "', " +
                "status = 1 " +
                "WHERE Regno = '" + regno + "' AND " +
                "vendor_code = '" + vendor + "' AND " +
                "partno = '" + partno + "'";

            myDB.ExecuteSQL(strSQL);
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {

        }
    }
}

记录错误消息：

2017-01-18 15：30：53,303 [1] ERROR DrawingRequestEmail.Util [（null）] - ReceiveEmail System.NullReferenceException：未将对象引用设置为对象的实例。在D：\ TFS \ SERVER \ Logistics \ Main \ MM \ DrawingRequest \ DrawingRequestEmail \ DrawingRequestEmail \ Email.cs中的DrawingRequestEmail.Email.ProcessEmailFromSubconSystem（MailItem消息）：第155行在D：\ TFS \ SERVER \ Logistics \ Main \ MM \ DrawingRequest \ DrawingRequestEmail \ DrawingRequestEmail \ Util.cs中的DrawingRequestEmail.Util.ReceiveEmail（）：第123行

Util.cs：第123行

class RFQHandler
{
    public static DataTable GetRequestDetail(string requestNumber, string vendorCode)
    {
        string connectionString = Config.DrawingConnString();
        SqlConnection sqlConnection = new SqlConnection(connectionString);
        string commandText = "SELECT * FROM vw_drawing_req_status WHERE regno = @requestNumber AND vendorcode = @vendorCode";
        SqlCommand sqlCommand = new SqlCommand(commandText, sqlConnection);
        sqlCommand.Parameters.Add("@requestNumber", SqlDbType.Char, 12).Value = requestNumber;
        sqlCommand.Parameters.Add("@vendorCode", SqlDbType.VarChar, 25).Value = vendorCode;
        DataTable requestDetail = new DataTable();
        using (sqlConnection)
        using (sqlCommand)
        {
            sqlConnection.Open();
            using (SqlDataReader sqlDataReader = sqlCommand.ExecuteReader())
            {
                requestDetail.Load(sqlDataReader);
            }
        }
        return requestDetail;
    }
}

Email.cs：第155行

ret = email.ProcessEmailFromSubconSystem(oMessage);

Answer 1

可能的空引用错误，我可以看到 -

    DataSet ds = new DataSet();
    string strSQL = string.Empty;
    ATSSPCommon.SQLDB myDB = null;
    string ret = string.Empty;
    try
    {
        ........
        ds = myDB.GetDataSet(strSQL);
    }
    catch (Exception ex)
    {
        ....
    }
    finally
    {

    }
    if (ds.Tables[0].Rows.Count > 0) // this could be the error
        return ds.Tables[0];
    else
        return null;

即使查询执行，也无法保证DataTable内部至少有一个DataSet，DataSet本身也可能为空。尝试添加这样的空检查 -

if (ds != null && ds.Tables.Any() && ds.Tables[0].Rows.Count > 0) 
        return ds.Tables[0];
    else
        return null;

在此声明之后也没有空检查 -

myDB = new ATSSPCommon.SQLDB(strConnectionString);

myDB也可能为空。

更新：对于.net 2.0，请在评论中提及ds.Tables.Count > 0而不是ds.Tables.Any()。

Answer 2

我也得到了一个无意义的NULL异常，当我使用“Set Next Statement”（Ctrl + Shift + F10）时，我将其追溯到调试器跳过的变量声明。

例如，我的代码如下所示：

if (false)
{
    classTypeObject myObject;
    myObject = someValue;
}

如果我在条件上设置断点然后移动下一个语句在开括号上运行，当设置myObject的值时，我得到一个空引用异常，因为调试器必须跳过声明。 / p>

但是，如果我将代码更改为这样并执行相同的调试步骤则没有问题：

classTypeObject myObject;
if (false)
{
    myObject = someValue;
}

P.S。显然这是伪代码，你永远不想硬编码if (false)。

NullReferenceException但没有null

2 个答案: