Simple Write

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Simple Write Example

The following example builds upon the Tutorial - using with VB.NET.

Writing to a Single Tag:

Simply copy & paste the code below into the Form_load() event:

   '
   'the following constants are used here to help make the code more readable
   'from an educational perspective.
   'Feel free to modify the contents of the values below.
   Const strPCName = ""
   Const strOPCServer = "OPCLabs.KitServer.2"
   Const strTag = "Simulation.Register_I4"
   Const iDataType = 0
   Const iNewValue = 10

   Try
   '
   'define our OPC Web Client
   Dim objOWC As New OPCLabs.EasyOPCDANet.EasyDACOM
   '
   'now to make the call to read the tag
   objOWC.WriteItemValue(strPCName, strOPCServer, strTag, iNewValue)
   '
   'now to show the value to the screen
   If Err.Number = 0 Then
   MessageBox.Show("Write Successful!")
   Else
   MessageBox.Show("Write Failed: " & Err.Number & ", " & Err.Description)
   End If
   '
   'now to destroy the objects
   objOWC = Nothing
   '
   Catch ex As Exception
   '
   'display an exception to screen
   MessageBox.Show(ex.Message)
   End Try

Writing to Multiple Tags within a single transaction:

   Try
   '
   'create ourselves an opc web client object
   Dim EasyDA As New OPCLabs.EasyOPCDANet.EasyDACOM

   '
   'create an array to store the results of our write instruction
   Dim Results As Array

   '
   'now perform the writes.
   'You will see that I have broken down this one line instruction over several lines for
   'readability sake. There are essentially 4 parameters:
   ' (1) the machine name, which is blank here
   ' (2) the opc server
   ' (3) the tags I want to write to
   ' (4) the values I want to write
   Results = EasyDA.WriteMultipleItemValues _
   ( _
   "", _
   "OPCLabs.KitServer.2", _
   New Object() {"Simulation.Register_I4", _
   "Simulation.Register_R8 ", _
   "Simulation.Register_BSTR"}, _
   New Object() {23456, _
   2.3456789, _
   "ABC"} _
   )

   '
   'now to construct some form of output message based on the results
   'of the write
   Dim strWriteValue As New System.Text.StringBuilder

   If Not Results Is Nothing Then

   '
   'iterate thru the array
   For I As Integer = LBound(Results) To UBound(Results)

   '
   'if the type of value is NOT an error
   If VarType(Results(I)) <> VariantType.Error Then

   '
   'not an error, so append our message with a "success"
   strWriteValue.Append("Element " & I & ": success")
   Else

   '
   'an error, so first RAISE the error accordingly
   EasyDA.RaiseError(Results(I))

   '
   'now record a message indicating (with as much info as poss.)
   'what the error was
   strWriteValue.Append(Err.Source & ": " & Err.Description _
   & " (0x" _
   & Hex(Err.Number ) & ")" & " **")
   End If

'
   'add a carriage-return + linefeed to the message
strWriteValue.Append(vbCrLf)
   Next
   End If

   '
   'display the message to screen
   TextBox1.Text = strWriteValue.ToString

   Catch ex As Exception
   'display exceptions to screen
   MessageBox.Show("Error: " & ex.Message)
   End Try

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