Object cannot be cast from DBNull to other types
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", 开发者_开发问答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;
}
}
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);
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
}
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
...
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;
}
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.
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"]);
}
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.
That's also worked for me:
- reservation.IsFull = rdr["isfull"] is DBNull ? false : (bool)rdr["isfull"];
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