如何从另一个具有void方法的类更新表单中的标签？

Question

Right now, I have a form with a label, lblHeartBeat. I have a UDP listener that takes in data with the value for lblHeartBeat. I'm wondering, how can I change the label in realtime with my UDP client from another class?

Right now I have

private void btnBopIt_Click(object sender, EventArgs e)
{
    string name;
    name=txtName.Text;
    UDPListener myListener=new UDPListener();
    myListener.GetData(name);
}

and the section of my class with the UDP client is:

public class UDPListener
{
public void GetData(string Name)
...
while (!done)
{
    byte[] bytes = listener.Receive(ref groupEP);
    var result = Encoding.ASCII.GetString(bytes, 0, bytes.Length);
    var data = result.Split(',')
        .Select(x => x.Trim().Split('='))
        .ToDictionary(x => x[0], x => x[1]);

    string myFunString = result.ToString();

    if (myFunString.Contains(Name) == true && myFunString.Contains("Heartbeat"))
    {
       decimal value=data["Hearbeat"] 
       //I'd like to have it some way below that:
       form1.lblHeartbeat=value;
    }
}

Mind you that my UDPlistener is a void method. I figure having it decimal will only return one value to the form, and not autoupdate. Should I try to create an event within the if statement so that it changes the label? Cheers

Update: I should also note that my UDP Listener takes on the string from txtName.Text. I may have to run this asynchronously. Update2: Finally got it to work. In addition to Rob's answer, I had to invoke it as I made my UDPlistiner operate on a different thread

Answer 1

Here:

UDPListener myListener=new UDPListener();

You should either pass the form, or the particular label you're interested in. Then your UDPListener would be able to reference the form and its controls. For example:

private void btnBopIt_Click(object sender, EventArgs e)
{
    UDPListener myListener = new UDPListener(this);
}

public class UDPListener 
{
    private Form1 _form { get; set; }
    public UDPListener (Form1 form) //Assuming your form class is `Form1`
    {
        _form = form;
    }

    //..

}

Then you can write this:

_form.lblHeartbeat.Text = value;

Assuming you declare your label as public

Answer 2

I would suggest slightly different approach.

Define an EventHandler in UDPListener and subscribe to that event in your main form.

public class UDPListener
{
     public event Action<string> MessageReceived;

     ...         
}

In your ( while )loop modify your code to notify to listeners.

 if (myFunString.Contains(Name) == true && myFunString.Contains("Heartbeat"))
 {
      decimal value=data["Hearbeat"] 
      //I'd like to have it some way below that:
      if(MessageReceived != null) MessageReceived(value); 
 }

Final step, subscribing to this event in Form1

private void btnBopIt_Click(object sender, EventArgs e)
{
     UDPListener myListener=new UDPListener();
     myListener.MessageReceived += (s) => lblHeartbeat.Text = s;
}