object reference error

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C#

if (dr.HasRows)
              {
                  while (dr.Read())
                  {
                      list.Add(new VechicleMappingObject()
                      {
                          Map_VechicleCode = Convert.ToInt32(dr["IE_VECHICLE_CODE"].ToString()),
                          Uw_VechicleCode = Convert.ToInt32(dr["UW_VEHICLE_CODE"].ToString()),
                          Map_MakeCode = dr["VEHICLE_MAKE_CODE"].ToString(),
                          Map_ModelCode = dr["VEHICLE_MODEL_CODE"].ToString(),
                          Map_SubTypeCode = dr["VEHICLE_SUBTYPE_CODE"].ToString(),
                          ServiceName = dr["ServiceName"].ToString()
                      });
                  }
              }

its getting the data from the database but when i use 2 add the data 2 the list its was throwing an onject reference is not instance.... pls help me

Thank u in adv

Posted 11-Sep-13 21:38pm

naveen pallela

Updated 11-Sep-13 21:42pm

TheUltimateDebugger

v2

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ArunRajendra 12-Sep-13 3:40am

I guess one of the field is having NULL. Hence ToString is throwing object reference error. Identify and handle the NULL data.

Dholakiya Ankit 12-Sep-13 7:01am

agree

Anurag Sinha V 12-Sep-13 3:44am

Yep..good point

2 solutions

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phil.o · Answer 1 · 2013-09-11T21:48:00

Solution 1

You may check the value of each nullable column in your DataReader.
For example, suppose that in your database the column ServiceName can be null:

C#

ServiceName = (dr["ServiceName"] != null) ? dr["ServiceName"].ToString() : string.Empty;

Posted 11-Sep-13 21:48pm

phil.o

Comments

Faisalabadians 12-Sep-13 9:34am

Nice one, each row should be checked against dbnull value

phil.o 12-Sep-13 10:56am

More precisely, each nullable column (ie. DBNull value is accepted by the database engine for this specific column) should be checked for null if any method/property has to be called on the DataReader column value.
For example, if ServiceName was declared as object, it would be OK to write ServiceName = dr["ServiceName"];.
But here, as the ToString() method is called, dr["ServiceName"] must not be null.

abdussalam143 · Answer 2 · 2013-09-11T22:05:00

C#

if (dr.HasRows)
              {
                  while (dr.Read())
                  {
                      list.Add(new VechicleMappingObject()
                      {
                          Map_VechicleCode = Convert.ToInt32(dr["IE_VECHICLE_CODE"].ToString()),
                          Uw_VechicleCode = Convert.ToInt32(dr["UW_VEHICLE_CODE"].ToString()),
                          Map_MakeCode = dr["VEHICLE_MAKE_CODE"].ToString(),
                          Map_ModelCode = dr["VEHICLE_MODEL_CODE"].ToString(),
                          Map_SubTypeCode = dr["VEHICLE_SUBTYPE_CODE"].ToString(),
                          ServiceName = dr["ServiceName"].ToString()
                      });
                  }
              }
<pre lang="c#">
                          Map_VechicleCode = Convert.ToInt32(dr["IE_VECHICLE_CODE"].ToString()),
                          Uw_VechicleCode = Convert.ToInt32(dr["UW_VEHICLE_CODE"].ToString()),

please check these two column (["IE_VECHICLE_CODE"],["UW_VEHICLE_CODE"]) the value or values are not coming in integer format.