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Back to Services Source Examples
Writing to Tags in an NT Service application using OPC Web Client Web Service
' Try
'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.Random"
Const iDataType = 0
Const iNewValue = 10
Try
'
'define our OPC Web Client
Dim objOWC As New EasyDAWS
'
'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 webex As Web.Services.Protocols.SoapException
'display exception to screen
If webex.InnerException Is Nothing Then
MessageBox.Show(webex.Message)
Else
MessageBox.Show(webex.InnerException.Message)
End If
Catch ex As Exception
'
'display an exception to screen
If ex.InnerException Is Nothing Then
MessageBox.Show(ex.Message)
Else
MessageBox.Show(ex.InnerException.Message)
End If
End Try
'
'create ourselves an opc web client object
Dim EasyDA As New OPCLabs.EasyOPCDANet.EasyDAWS
'
'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() _
{ _
10, _
20, _
30 _
} _
)
'
'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 webex As Web.Services.Protocols.SoapException
'display exception to screen
If webex.InnerException Is Nothing Then
MessageBox.Show(webex.Message)
Else
MessageBox.Show(webex.InnerException.Message)
End If
Catch ex As Exception
'
'display an exception to screen
If ex.InnerException Is Nothing Then
MessageBox.Show(ex.Message)
Else
MessageBox.Show(ex.InnerException.Message)
End If
End Try
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