Object cannot be cast from DBNull to other types

Question

Object cannot be cast from DBNull to other types   I have a following function which throws the above error  I am handling all nulls in store procedure and in the C  code   So where is it getting this error   I can see the error in the catch block  But i am not understanding which line in the following create   getting the error   public Boolean Create DataTO DataTO        IDbTrans transaction   null      IDbCmd IDbCmd       string EncryptedPassword   Encrypt DataTO txtPwd       Base dataAccCom   null       try               dataAccCom   Factory Create            dataAccCom OpenConnection            transaction   dataAccCom BeginTransaction            IDbCmd   dataAccCom CreateCommand  sp Register   true           dataAccCom AddParameter IDbCmd   op Id   DbType Int64  0  ParameterDirection Output           dataAccCom AddParameter IDbCmd   p dlstTitle   DbType String  ReplaceNull DataTO dlstTitle            dataAccCom AddParameter IDbCmd   p txtFirstName   DbType String  ReplaceNull DataTO txtFirstName            dataAccCom AddParameter IDbCmd   p txtMiddleName   DbType String  ReplaceNull DataTO txtMiddleName            dataAccCom AddParameter IDbCmd   p txtLastName   DbType String  ReplaceNull DataTO txtLastName            dataAccCom AddParameter IDbCmd   p txtDob   DbType DateTime  DataTO txtDob           dataAccCom AddParameter IDbCmd   p txtDesig   DbType String  ReplaceNull DataTO txtDesig            dataAccCom AddParameter IDbCmd   p txtOFlatNo   DbType String  ReplaceNull DataTO txtOFlatNo            dataAccCom AddParameter IDbCmd   p txtOBuild   DbType String  ReplaceNull DataTO txtOBuild            dataAccCom AddParameter IDbCmd   p txtOPost   DbType String  ReplaceNull DataTO txtOPost            dataAccCom AddParameter IDbCmd   p txtOArea   DbType String  ReplaceNull DataTO txtOArea            dataAccCom AddParameter IDbCmd   p txtOCity   DbType String  ReplaceNull DataTO txtOCity            dataAccCom AddParameter IDbCmd   p txtRBuild   DbType String  ReplaceNull DataTO txtRBuild            dataAccCom AddParameter IDbCmd   p txtRPost   DbType String  ReplaceNull DataTO txtRPost            dataAccCom AddParameter IDbCmd   p txtUserID   DbType String ReplaceNull DataTO txtUserID            dataAccCom AddParameter IDbCmd   p txtPwd   DbType String  ReplaceNull EncryptedPassword            dataAccCom ExecuteNonQuery IDbCmd           DataTO Id   Convert ToInt64 dataAccCom GetParameterValue IDbCmd   op Id             transaction Commit            return true               catch  System Exception ex                if  transaction    null                        transaction Rollback                      throw ex            finally               transaction   null          if  dataAccCom    null                        dataAccCom CloseConnection                      dataAccCom   null          IDbCmd   null           public string ReplaceNull string value        if  value    null                return               else               return value           public DateTime ReplaceNull DateTime value        if  value    null                return DateTime Now            else               return value           public double ReplaceNull double value        if  value    null                return 0 0            else               return value

User · Accepted Answer

I m thinking that your output parameter is coming back with a DBNull value  Add a check for that like this  var outputParam   dataAccCom GetParameterValue IDbCmd   op Id    if   outputParam is DBNull        DataTO Id   Convert ToInt64 outputParam

User · Answer

I suspect that the line  DataTO Id   Convert ToInt64 dataAccCom GetParameterValue IDbCmd   op Id       is causing the problem   Is it possible that the op Id value is being set to null by the stored procedure   To Guard against it use the Convert IsDBNull method   For example   if   Convert IsDBNull dataAccCom GetParameterValue IDbCmd   op Id       DataTO Id   Convert ToInt64 dataAccCom GetParameterValue IDbCmd   op Id       else     DataTO Id      some default value or perform some error case management

User · Answer

You need to check for DBNull  not null  Additionally  two of your three ReplaceNull methods don t make sense  double and DateTime are non-nullable  so checking them for null will always be false

User · Answer

Reason for the error  In an object-oriented programming language  null means the absence of a reference to an object  DBNull represents an uninitialized variant or nonexistent database column  Source MSDN  Actual Code which I faced error   Before changed the code       if  ds Tables 0  Rows 0  0     null        Which is not working                     seqno    1               else                 seqno   Convert ToInt16 ds Tables 0  Rows 0  0     1           After changed the code      if  ds Tables 0  Rows 0  0     DBNull Value     which is working properly                               seqno    1                          else                                 seqno   Convert ToInt16 ds Tables 0  Rows 0  0     1                   Conclusion  when the database value return the null value  we recommend to use the DBNull class instead of just specifying as a null like in C  language

User · Answer

TryParse is usually the most elegant way to handle this type of thing   long temp   0  if  Int64 TryParse dataAccCom GetParameterValue IDbCmd   op Id   ToString    out temp        DataTO Id   temp

User · Answer

For others that arrive on this page from google   DataRow also has a function  IsNull  ColumnName        public DateTime  TestDt       public Parse DataRow row                if   row IsNull  TEST DT                TestDt   Convert ToDateTime row  TEST DT

User · Answer

I faced this problem today and resolved it by checking the mapping class  I had a class which had 5 properties to which 5 columns returned from stored procedure were being mapped  Those properties were non-nullable and due to which i was getting the error  I made them nullable and the issue resolved       public int  Pause   get  set        public int  Delay   get  set        public int  Transition   get  set        public int  TransitionTime   get  set        public int  TransitionResolution   get  set      Added     with data type to made them nullable    Secondly i also added isNull check in the stored procedure as well as follows       isnull co pivot Pause  0  as Pause      isnull co pivot Delay  0  as Delay      isnull co pivot Transition  0  as Transition      isnull co pivot TransitionTime  0  as TransitionTime      isnull co pivot TransitionResolution  0  as TransitionResolution   Hope this helps someone

[c#] Object cannot be cast from DBNull to other types

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