get the output from stored Procedure

CREATE PROCEDURE dbo.AddNewPerson
	(
	
	
	@FirstName nvarchar(50),
	
	@LastName nvarchar(50),
	@dateofbirth nvarchar(50),
		@Mrn int OUTPUT
		
	)
AS

BEGIN 



INSERT INTO Person(FirstName,LastName,dateofbirth)
		                         VALUES        (@FirstName,@LastName,@dateofbirth)
	 
		SELECT  @Mrn=SCOPE_IDENTITY();
		Return @Mrn
	END

	RETURN

SortedList SL = new SortedList();
       
        SL.Add("@FirstName", FirstName);
        SL.Add("@LastName", LastName);
        SL.Add("@dateofbirth", dateofbirth);
               

        ProcedureName = "AddNewPerson";
        if (db.RunProcedure(ProcedureName, SL) == 1)
            return true;
        else
            return false;
    }