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Back to Services Source Examples
Reading & Writing Tags of Array type using OPCData.NET Components
Introduction The following examples show you how you can read/write to Tags that are of type Array, from an NT Service application. ' '
'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
'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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