Basic Stored Procedure ??

ALTER PROCEDURE dbo.SelectItems
(@PRN NVARCHAR(7))
AS

SELECT eName AS EName, ePRN, cID, eCC, SUBSTRING(sDate, 7, 2) AS Day, SUBSTRING(sDate, 5, 2) AS Month, SUBSTRING(sDate, 1, 4) AS Year, eLOC,
eTel, ePhone, eMobile, less20, over20, q1, inSVmn, inSVyr, inSVRetIns, outSVmn, outSVyr, outSVRetIns, insNo, q2, qper2, qplc2, q3, qper3, qplc3, q4,
qper4, qplc4, pic1, pic2, pic3, esigdt, CCHName, CCHTitle, CCHsigdt, username, levent, eventdate, eventtime
FROM iTrns
Where ePRN = @PRN
RETURN

===

My code behind is

SqlConnection SqlCon = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["hrdbConnectionString1"].ConnectionString);
String SQL = "EXECUTE SelectItems";
SqlDataAdapter Adptr = new SqlDataAdapter(SQL, SqlCon);
SqlCommandBuilder CB = new SqlCommandBuilder(Adptr);
DataSet ds = new DataSet();
Adptr.Fill(ds);
return ds;
SqlCon.Close();

Where I tried to search for PRN by using TextBox it gives me error

Procedure or Function 'SelectItems' expects parameter '@PRN', which was not supplied

I checked the Stored Proc and it was fine. So I guess the problem in the code behind

Any