Question

I need to pass data with an event. Currently, when receiving more data (via comport), the event will fire but the previous event (&data) is not handled yet, so the data gets overwritten.
How can I handle the event &data in a safe way? I have multiple events like this (15x), so I am not sure if using a queue for the data is the best way or pass data along with the event (like S.O. item 4215845).

Example (this example is with a string, but I also use arrays, bools etc):

At the ‘sender’ side (class1):

public event EventHandler evDiaStringMessage = delegate { };
private void evDiaStringMessageEvent()
{
    evDiaStringMessage(this, new EventArgs());
}
private static string _DiaString;
public string DiaString
{
    get { return _DiaString; }
    set { _DiaString = value; }
}

DiaString contains the data and gets overwritten when evDiaStringMessage is fired too soon.

At the ‘receiver / GUI’ side (class2):

dia.evDiaStringMessage += new EventHandler(dia_evDiaStringMessage);

private delegate void dia_evDiaStringMessageCallBack(object sender, EventArgs e);
void dia_evDiaStringMessage(object sender, EventArgs e)
{
    if (this.InvokeRequired)
    {
        this.BeginInvoke(new dia_evDiaStringMessageCallBack(dia_evDiaStringMessage), new object[] { sender, e});
    }
    else
    {
        frmcomm.CommTextBox("Receiver message: " + dia.DiaString + "\r\n", Color.Red);
    }
}

dia.DiaString does not contain the expected data (previous data), but all events are ‘received’.

Your help is very much appreciated! Even more with an example!

Edit:

I changed the code to:

At the ‘sender’ side (class1):

public event EventHandler<DiaStringEventArgs> evDiaStringMessage ;
public class DiaStringEventArgs : EventArgs
{
    public string DiaString  { get; set; }
}

private void evDiaStringMessageEvent(DiaStringEventArgs e)
{
    EventHandler<DiaStringEventArgs> handler = evDiaStringMessage;
    if (handler != null)
        handler(this, e);
}

…

private void PrepareDataAndFireEvent()
{
    DiaStringEventArgs args = new DiaStringEventArgs(); 
    args.DiaString = ByteToString(data);
    evDiaStringMessageEvent(args);
}

At the ‘receiver / GUI’ side (class2):

dia.evDiaStringMessage += new EventHandler<ifDiA10.DiaStringEventArgs>(dia_evDiaStringMessage);

private delegate void dia_evDiaStringMessageCallBack(object sender, ifDiA10.DiaStringEventArgs e);
void dia_evDiaStringMessage(object sender, ifDiA10.DiaStringEventArgs e)
{
    if (this.InvokeRequired)
    {
        this.BeginInvoke(new dia_evDiaStringMessageCallBack(dia_evDiaStringMessage), new object[] { sender, e});
    }
    else
    {
        frmcomm.CommTextBox("Receiver message: " + e.DiaString + "\r\n", Color.Red);
    }
}

Answer 1

You can store your data in a custom EventArgs class:

public class ReceivedDataEventArgs : EventArgs
{
   // Add the properties you require
}

The event is defined like so:

public event EventHandler<ReceivedDataEventArgs> ReceivedData;

Your handler will take in an instance your class instead of the EventArgs object, and hence you’ll have the correct data.