Null reference exception

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i am deleting a record from database. Before deleting i am checking whether the record has any reference to another table. IF not i am deleting the record.
I am getting the error "nullreferenceexception was unhandled by user code" even though the record is deleted.
I am returning a string from the stored procedure.

Can anyone give a solution for this?

SQL

DECLARE @temp as int;
-- Insert statements for procedure here
SELECT @temp = (SELECT CAST(COUNT(1) AS BIT) AS Expr1
FROM ALARM_MSTR_ALARM_DETAIL
WHERE ALARM_TYPE_ID = @ALARM_TYPE_ID)

IF @temp <> 1
BEGIN
Delete from ALARM_MSTR_ALARM_TYPE where ALARM_TYPE_ID = @ALARM_TYPE_ID
END
ELSE
SET @temp = 0;	
RETURN @temp

C#

public string DeleteAlarmType(int iAlarmId)
{
SqlParameter[] ParamAdd = new SqlParameter[1];
ParamAdd[0] = new SqlParameter("@ALARM_TYPE_ID", iAlarmId);
 
return SqlHelper.ExecuteScalar(ConfigurationManager.ConnectionStrings["MetaConnectionString"].ConnectionString, CommandType.StoredProcedure, "Delete_alarm_master_type", ParamAdd).ToString();
}

Posted 20-May-14 23:40pm

Member 10755410

Updated 21-May-14 0:23am

Kornfeld Eliyahu Peter

v2

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Kornfeld Eliyahu Peter 21-May-14 5:54am

Show the code - including the line with the error!

Member 10755410 21-May-14 6:19am

public string DeleteAlarmType(int iAlarmId)
{
SqlParameter[] ParamAdd = new SqlParameter[1];
ParamAdd[0] = new SqlParameter("@ALARM_TYPE_ID", iAlarmId);

return SqlHelper.ExecuteScalar(ConfigurationManager.ConnectionStrings["MetaConnectionString"].ConnectionString, CommandType.StoredProcedure, "Delete_alarm_master_type", ParamAdd).ToString();
}

I am getting error in the return statement.

Animesh Datta 21-May-14 5:55am

provide store procedure and post some code where you got the error

Member 10755410 21-May-14 6:20am

DECLARE @temp as int;
-- Insert statements for procedure here
SELECT @temp = (SELECT CAST(COUNT(1) AS BIT) AS Expr1
FROM ALARM_MSTR_ALARM_DETAIL
WHERE ALARM_TYPE_ID = @ALARM_TYPE_ID)

IF @temp <> 1
BEGIN
Delete from ALARM_MSTR_ALARM_TYPE where ALARM_TYPE_ID = @ALARM_TYPE_ID
END
ELSE
SET @temp = 0;
RETURN @temp

public string DeleteAlarmType(int iAlarmId)
{
SqlParameter[] ParamAdd = new SqlParameter[1];
ParamAdd[0] = new SqlParameter("@ALARM_TYPE_ID", iAlarmId);

return SqlHelper.ExecuteScalar(ConfigurationManager.ConnectionStrings["MetaConnectionString"].ConnectionString, CommandType.StoredProcedure, "Delete_alarm_master_type", ParamAdd).ToString();
}

Member 10755410 21-May-14 6:27am

DECLARE @temp as int;
-- Insert statements for procedure here
SELECT @temp = (SELECT CAST(COUNT(1) AS BIT) AS Expr1
FROM ALARM_MSTR_ALARM_DETAIL
WHERE ALARM_TYPE_ID = @ALARM_TYPE_ID)

IF @temp <> 1
BEGIN
Delete from ALARM_MSTR_ALARM_TYPE where ALARM_TYPE_ID = @ALARM_TYPE_ID
SET @temp = 0;
END

RETURN @temp

Telstra 21-May-14 6:20am

where is return statement in your code? what you are returning

Member 10755410 21-May-14 6:27am

I am returning a integer from the stored procedure. i tried to convert it to integer in the function but even then i am getting the same error.

3 solutions

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*dan!sh* · Answer 1 · 2014-05-21T00:35:00

Solution 2

ExcecuteScalar returns null if there is no data returned by the queries in the stored procedure.

Posted 21-May-14 0:35am

dan!sh

Comments

Member 10755410 21-May-14 6:38am

ok but how do we handle it in the code. i have to do some operations based on the return value.

Kornfeld Eliyahu Peter · Answer 2 · 2014-05-21T00:25:00

Solution 1

There are several points where null reference exception can occur:
1. ConfigurationManager.ConnectionStrings["MetaConnectionString"].ConnectionString - check your connection string(s) in config file
2. SqlHelper.ExecuteScalar().ToString() - maybe ExecuteScalar returns null?! debug it

Posted 21-May-14 0:25am

Kornfeld Eliyahu Peter

Comments

Member 10755410 21-May-14 6:32am

I checked it and it is returning null only. How to handle null value there?

Kornfeld Eliyahu Peter 21-May-14 7:32am

That's a question you have to ask yourself! What the meaning of 'no data' when executing the SQL query...
After you answer the question you will be able to forge a solution...

appoos · Answer 3 · 2014-05-21T01:54:00

Solution 3

In your storedprocedure instead of Return @temp use Select @temp

Posted 21-May-14 1:54am

appoos