SqlCommand, passing something that could be null - sql-server

Question

I have a SQL command that I've been asked to modify, and I'm having some troubles with the fact that what I'm passing to the SQL can now be null. If I'm passing a value, I can rely on the columnName = #parameterName in the SQL, but with NULL, I can't pass null or DBNull and have it correctly resolve.
Here's the SQL pseudocode:
SELECT
Columns
FROM
ClientSetup
WHERE
Client_Code = #ClientCode AND
Package_Code = #PackageCode AND
Report_Code = #ReportCode
The problem is that now #ReportCode can validly be NULL. In my C# code where I set up the SqlCommand, I can put in:
cmd.Parameters.Add("#ReportCode", SqlDBType.VarChar, 5).Value = reportType;
//reportType is a string, which can be null
But, if reportType is null, I need to use Report_Code IS NULL in the SQL, rather than Report_Code = #reportCode.
The solution I've found is to change the last where clause to the following:
((#ReportCode IS NULL AND Report_Code IS NULL) OR Report_Code = #ReportCode)
and the parameter phrase to
cmd.Parameters.Add("#ReportCode", SqlDBType.VarChar, 5).Value = string.IsNullOrEmpty(reportType) ? System.DBNull : reportType;
What this does works, but I was wondering if anyone knew of a cleaner or better way to handle nullable parameters when passing things to SQL from .NET code.

Answer 1

The short answer is that no, the SqlClient API requires you to pass in a DbNull.Value for NULL parameter values.
But I have some doubts about how you treat NULLs. For one you use string.IsNullOrEmpty which means that you treat the emtpy string as a NULL. This is questionable, there may be legitimate empty string values in the database.
My second concern is the logic of matching NULLs in the database. More often than not passing in a NULL parameter means that the request is interested in any value, not specifically in NULL values. I'm not saying your logic of matching NULL parameters to NULL values is flawed, I just want to make sure you know what you're doing.

Answer 2

Much of a muchness, in the past I've built the query
test reportcode for null if is its replace ReportCode = #ReportCode with "ReportCode is Null"
add the reportcode parameter if it isn't.
Generally though ReportCode of null signalled I wanted to select based on the other parameters and didn't care what the null one was.
It's a bit naughty
but Where IsNull(ReportCode,'') = IsNull(#ReportCode,'')
would give you what you want, given you are using IsNullOrEmpty.

Answer 3

Well, is correct the way how you fix it
only is (#ReportCode IS NULL AND Report_Code IS NULL) not is neccesary. because it is not c# o c++.
Some how that should be finally result
SELECT
Columns
FROM
ClientSetup
WHERE
Client_Code = #ClientCode
AND Package_Code = #PackageCode
AND (Report_Code = #ReportCode or #ReportCode is null)