Question

I have a class as follows:

class TestSomeData
{
    public string someString;
    public void CheckSomeStuff()
    {
         foreach(string x in someList)
         {
              someString = x;
          }
     }
 }

What i want to do is this:

TestSomeData test = new TestSomeData;
test.CheckSomeStuff();
label1.Content = test.someString;

So if x is 1,2,3,4,5 out of someList in CheckSomeStuff, i need the label1.Content to reflect that, but from a different class. how do i do that?

Answer 1

A class can inform other classes of changes made to it by declaring events

public class SomeDataClass
{
    public event EventHandler SomeDataChanged;

    private string _someData;
    public string SomeData
    {
        get { return _someData; }
        set
        {
            if (value != _someData) {
                _someData = value;
                OnSomeDataChanged();
            }
        }
    }

    private void OnSomeDataChanged()
    {
        SomeDataChanged?.Invoke(this, EventArgs.Empty);
    }
}

class InterestedClass
{
    public void Work()
    {
        var someData = new SomeDataClass();
        someData.SomeDataChanged += someData_SomeDataChanged;
        someData.SomeData = "New Value";
    }

    void someData_SomeDataChanged(object sender, EventArgs e)
    {
        Console.WriteLine("Some data changed: {0}", ((SomeDataClass)sender).SomeData);
    }
}

You could also make the event static. This would allow a listener to listen to changes of any instance of this class.

SomeDataClass.SomeDataChanged += SomeDataClass_SomeDataChanged;

var someData = new SomeDataClass();
someData.SomeData = "New Value";
var someOtherData = new SomeDataClass();
someData.SomeData = "Other Value";