Tag.Changed Event

Data Change Event

Remarks

The Changed event fires when the Tag changes value or Quality state

Example

VB
' ******************************
' * Initialize Controller and Tag
Dim MyPLC As New ABLink.Controller("192.168.1.32")
Dim WithEvents MyTag As New ABLink.Tag("N7:0")
Try
 ' *****************************
 ' * add event handler
  AddHandler MyTag.Changed, AddressOf MyTag_Changed 
  
  ' ****************************
  ' * read tag
  MyPLC.ReadTag(MyTag)
Catch ex As System.Exception
  Console.WriteLine(ex.Message)
End Try
{...elsewhere in code...}
' *********************************
' * event handler
Private Sub MyTag_Changed(ByVal sender As Object, ByVal e As System.EventArgs)
  Try
  
   Dim theTag as ABLink.Tag
   Dim args as ABLink.DataChangeEventArgs
   
   ' ***************************
   ' * Tag that caused the event 
   theTag = sender
   
   ' ***************************
   ' * event argument parameters
   args = e
   
   ' ***************************
   ' * process the event data
   If ResultCode.QUAL_GOOD = args.QualityCode Then
      Console.WriteLine(Convert.ToString(args.Value))
      Console.WriteLine(args.TimeStamp.ToString())
   Else
      Console.WriteLine(args.ErrorString)
   End If
   Console.WriteLine(args.QualityString)
 Catch ex As System.Exception
   Console.WriteLine(ex.Message)
 End Try
End Sub


 


C#
///////////////////////////
// initialize controller and tag
ABLink.Controller MyPLC = new ABLink.Controller("192.168.1.32");
ABLink.Tag MyTag = new ABLink.Tag("N7:0");
try
{
  ///////////////////////////
  // add event handler
  MyTag.Changed +=new EventHandler(MyTag_Changed);
  
  ///////////////////////////
  // read the tag
  MyPLC.ReadTag(MyTag);
}
catch(System.Excpetion ex)
{
  Console.WriteLine(ex.Message);
}
{...elsewhere in code...}
/////////////////////////////////////
// EVENT HANDLER
private void MyTag_Changed(object sender, EventArgs e)
{
  try
  {
    //////////////////////////////////////
    // Tag that caused the event
    ABLink.Tag theTag = (ABLink.Tag)sender;
    
    //////////////////////////////////////
    // event argument parameters
    ABLink.DataChangeEventArgs args = (ABLink.DataChangeEventArgs)e;
    
    /////////////////////////////////////
    // process the event data
    if(ResultCode.QUAL_GOOD == args.QualityCode)
    {
       Console.WriteLine(Convert.ToString(args.Value));
       Console.WriteLine(args.TimeStamp.ToString());
    }
    else
       Console.WriteLine(args.ErrorString);
    Console.WriteLine(args.QualityString); 
  }
  catch (System.Exception ex)
  {
    Console.WriteLine(ex.Message);
  }
}           

See Also

Tag Class | ABLink Namespace | ReadTag | WriteTag | Active | GroupRead | GroupWrite