Question

The following code is the simplified version of my problem:

public partial class Form1 : Form
{
    BackgroundWorker bw;
    Class myClass = new Class();

    public Form1()
    {
        InitializeComponent();

        bw = new BackgroundWorker();
        bw.DoWork += new DoWorkEventHandler(bw_DoWork);
        label1.DataBindings.Add("Text", myClass, "Text", true, DataSourceUpdateMode.Never);
    }

    void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        myClass.Text = "Hi";
    }

    private void button1_Click(object sender, EventArgs e)
    {
        bw.RunWorkerAsync();
    }
}

public class Class : INotifyPropertyChanged
{
    private string _Text;

    private void SetText(string value)
    {
        if (_Text != value)
        {
            _Text = value;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public string Text
    {
        get { return _Text; }
        set { SetText(value); OnPropertyChanged(new PropertyChangedEventArgs("Text")); }
    }

    protected void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null) PropertyChanged(this, e);
    }
}

What happens is that when I click the button1 (which invokes button1_Click) the text in label1 doesn’t update. This is because the label1.Text property is internally trying to be changed from my BackgroundWorker‘s thread, which internally causes an exception. What would it be the best way, in general, to fix this kind of problem? Which part of this code would you change if you must update my Class.Text property from a different thread but must also have a control binded to it?

Answer 1

Try this:

//This is the handler to execute the thread.
void DoWork(object sender, EventArgs a) {

 Action updateControl = ()=>myClass.Text = "Blah";

 if(myForm.InvokeRequired) {

    myForm.Invoke( updateControl);

 }
 else {updateControl();}

}

this routine executes on the background worker thread.