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 Web Service Consumption
The following examples show you how you can read and write to Tags that are of type Array.
 Reading an Array Tag:
'
'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 = "SWToolbox.TOPServer"
Const strTag = "Channel_1.Device_1.TagArray_1"
Const strAccessPath = ""
Const iDataType = 0
Try
'
'define our OPC Web Client web-service mode
Dim objOWC As New EasyOPCDANet.EasyDAWS
'
'define the object to receive the value, quality and timestamp
Dim objTagVTQ As EasyOPCDANet.IVTQNet
'
'now to make the call to read the tag
objTagVTQ = objOWC.ReadItem( _
strPCName, _
strOPCServer, _
strTag)
Dim strMessage As New System.Text.StringBuilder
'
'now to make sure the object is an array
If IsArray(objTagVTQ.Value) Then
'
'now to get the value into an array
Dim objArray As Array = objTagVTQ.Value
'
'now to store the values into a string for later
'displaying to screen
With strMessage
.Append("Value(s): ")
For i As Integer = 0 To objArray.GetLength(0) - 1
.Append(objArray(i))
If Not i = objArray.GetLength(0) - 1 Then .Append(", ")
Next
End With
Else
'
'display an error
strMessage.Append("The Tag that was read is NOT an array!")
End If
'
'display the message to screen
MessageBox.Show(strMessage.ToString)
'
'now to destroy the objects
objTagVTQ = Nothing
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
Writing to an Array Tag:
'
'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 = "SWToolbox.TOPServer"
Const strTag = "Channel_1.Device_1.TagArray_1"
Const iDataType = 0
Try
'define our OPC Web Client
Dim objOWC As New OPCLabs.EasyOPCDANet.EasyDAWS
'now to create an array of values to write to our tag
Dim arrValues() As Object = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
'now to write the array to the tag
objOWC.WriteItemValue( _
strPCName, _
strOPCServer, _
strTag, _
arrValues)
'now to make sure there was no error
If Err.Number = 0 Then
MessageBox.Show("Array Write successful!")
Else
MessageBox.Show("Error writing array (" & Err.Number & ") " & Err.Description)
End If
'now to dispose of our object
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
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