Home/ Questions/Resolved the problem of the ''object cannot be cast from dbnull to other types''.
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Lea Taylor
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Asked: 2022-05-18T19:43:35+00:00 In:

Resolved the problem of the ”object cannot be cast from dbnull to other types”.

  • 17

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I am tired of fixing the problem: object cannot be cast from dbnull to other types in the csharp; even if I get the reference from another forum, it still returns an error:

*** Start Block *** 
Object cannot be cast from DBNull to other types

To identify the problem, I will show you the detail here:

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;
  }
 }

How do I do that? Could you support me in improving this problem?

cannot be cast from dbnull to other types
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2 Answers

  1. Best Answer
    Expert

    The cause:

    After researching your problem for hours, I found that the parameter of your output is returning a value of DBNull. This is the reason why you have got the: ”object cannot be cast from dbnull to other types” error.

    Solution:

    The easiest solution for this error is adding a check for DBNull value as the following:

    var outputParam = dataAccCom.GetParameterValue(IDbCmd, "op_Id");
if(!(outputParam is DBNull))
DataTO.Id = Convert.ToInt64(outputParam);

    Another way that is equally effective is using the Convert.IsDBNull method:

    if (!Convert.IsDBNull(dataAccCom.GetParameterValue(IDbCmd, "op_Id"))
{
DataTO.Id = Convert.ToInt64(dataAccCom.GetParameterValue(IDbCmd, "op_Id"));
}
else
{
DataTO.Id = ...some default values or perform some cases of management error
}
    • 0

  2. It is possible that the line has been retracted. 

    DataTO.Id = Convert.ToInt64(dataAccCom.GetParameterValue(IDbCmd, "op_Id"));

    This is the root cause of the problem. It is possible that the op_Id value has been set to null by a stored procedure.

    Use the Convert.IsDBNull method to protect yourself. Take this 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
}
    • 22

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