Question about SQL Transaction/Stored Procedures and Identity Fields

[riechan]

Getting a "Procedure or function spNewPatient expects parameter @PXID (Identity Field) which was not supplied." when I try to insert data using dynamic SP and transactions. However, @PXID is an Identity field in tblPatient, so I didn't include it on the input parameters. Do I also have to begin a transaction here (since the stored procedure is technically a transaction)? Is that the reason why the @PXID is not generated by the stored procedure?

Public SQLParams As New List(Of SqlParameter)
Public Function ExecuteSP(SPName As String) As Integer
	Dim _ReturnVal As Integer
	Try
		SQLConn.Open()
		SQLCmd = New SqlCommand(SPName, SQLConn)
		SQLCmd.CommandType = CommandType.StoredProcedure

		For Each p As SqlParameter In SQLParams
			SQLCmd.Parameters.Add(p)
			SQLCmd.Parameters(p.ParameterName).Value = p.Value
		Next

		_ReturnVal = SQLCmd.ExecuteScalar()
		SQLConn.Close()
		Return _ReturnVal
	Catch ex As Exception
		MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Encountered Critical Error")
		If SQLConn.State = ConnectionState.Open Then SQLConn.Close()
		Return -1
	End Try
	
	FlushParams()
End Function

Public Sub AddParams(Name As String, Value As Object, Optional DataType As DbType = DbType.String)
	Dim newParams As New SqlParameter With {.ParameterName = Name, .Value = Value, .DbType = DataType}
	SQLParams.Add(newParams)
End Sub

USE [dbMacondo]
ALTER PROC [dbo].[spNewPatient]
	@PXID			int OUTPUT,
	<Input Variables>
AS
BEGIN
	BEGIN TRANSACTION
		BEGIN TRY
			INSERT INTO tblPatient (...)
			VALUES (...);

			SELECT @PXID = SCOPE_IDENTITY();
			COMMIT TRANSACTION
		END TRY

	BEGIN CATCH
		IF XACT_STATE() <> 0
			ROLLBACK TRANSACTION
	END CATCH
END

Edit: I changed the order of the fields in the stored procedure. It looks like none of the parameters I tried to pass from VB to SQL were transferred... I checked the list (SQLParams) and everything was in order.

Edit 2: Checked it again, and it's still looking for the @PXID Identity Field. Removed the @PXID in the stored procedure and everything went through nicely. However, how would I be able to implement this with using an output variable for scope_identity() in the stored procedure?