Reading variables from PLC (Beckhoff)

[busarider29]

This is not related to AdvancedHMI as I am not using it for this particular project that I have.  I need to read variables in the Beckhoff PLC from my .NET application.  I can write to the PLC from my .NET application but I am running into difficulties reading the variables.  I am using Structs to write variables to the PLC and I would like to stick to that convention when reading as well.  I have two thermocouple values that I need to read (iTC1_Val, iTC2_Val) that are in the PLC program.  These are in a Struct in the PLC and the .NET application. 

Thank you in advance for any assistance that can be provided.

'Create Structure in .NET application with the two variables

Code: [Select]

Public Structure ST_PLCAIChannelsINTS
        Public iTC1_Value As Short
        Public iTC2_Value As Short
    End Structure
'Create instance of the Structure, Ads objects for reading/writing, etc.

Code: [Select]

Public Class frmMain
    Private tcClient As TwinCAT.Ads.TcAdsClient
    Private dataStreamWrite As TwinCAT.Ads.AdsStream
    Private dataStreamRead As TwinCAT.Ads.AdsStream
    Private binaryReader As System.IO.BinaryReader
    Private binaryWriter As System.IO.BinaryWriter
    Private plcData6 As ST_PLCAIChannelsINTS
'Create same Struct in the PLC with same name with variables

Code: [Select]

TYPE ST_PLCAIChannelsINTS :
STRUCT
iTC1_Value : INT;
iTC2_Value : INT;
END_STRUCT
END_TYPE
'Create instance of the Struct in MAIN in the PLC

Code: [Select]

PROGRAM MAIN
VAR
st_PLCAIChannelsINTS : ST_PLCAIChannelsINTS;
END_VAR

'Read the PLC variables in this Sub.  This is what I have so far for code.  Is this correct?  What code syntax needs to go in the Try Catch block to perform the actual read?   

Code: [Select]

Private Sub ReadRegisters()
        Dim hvar As Integer
        Dim errorBits As New BitArray(Errors)
        dataStreamRead = New AdsStream(32)
        binaryReader = New BinaryReader(dataStreamRead)
        dataStreamRead.Position = 0

        Try
            hvar = tcClient.CreateVariableHandle("Main.st_PLCAIChannelsINTS.iTC1_Value")
            'Insert code for reading the PLC Struct variables here
        Catch ex As AdsErrorException
            MessageBox.Show(ex.Message, "ADS Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try

[Archie]

It has been many years since I've used the ADS communication library, but I think you are looking for something like this:

tcClient.Read(hvar, dataStreamRead)
dim MyValue=binaryreader.read?