C#

private WaitForm waitForm;
private delegate void CloseWaitFormDelegate();

private void StartProcess()
{
    Thread processThread = new Thread(new ThreadStart(Process));
    waitForm = new WaitForm();
    processThread.Start();
    waitForm.ShowDialog(this);
}

private void Process()
{
    // Process code here...
    CloseWaitFormDelegate closeWaitForm = new CloseWaitFormDelegate(CloseWaitForm);
    Invoke(closeWaitForm);
}

private void CloseWaitForm()
{
    if (waitForm != null)
    {
        waitForm.Close();
        waitForm = null;
    }
}

Form1.Enabled = false;
Form1.ShowWaitScreen();
Form1.DoMyWork();
Form1.CloseWaitScreen();
Form1.Enabled = true

V. wrote:

it always reads an item that is part of the datasource

public partial class Form1 : Form
    {
        ArrayList arr;

        public Form1()
        {
            InitializeComponent();
            arr = new ArrayList();
            arr.Add("hello");
            arr.Add("World");
            arr.Add("is");
            arr.Add("an");
            arr.Add("old");
            arr.Add("example");
            comboBox1.DataSource = arr;
        }
        
        private void button1_Click(object sender, EventArgs e)
        {
            MessageBox.Show(comboBox1.Text);
        }
}

V. wrote:

Can you add items to your datasource?

((IList)comboBox1.DataSource).Add(comboBox1.Text);

Nader Elshehabi wrote:

So, where is your problem??

DataView view = (DataView)mycombo.DataSource;<br />
DataRow r = view.Table.Rows[0];<br />
r[0] = mytext;	<br />
r[1] = -1;<br />
((IList<DataRow>)mycombo.DataSource).Add(r);

public void SomeOperation()
{
    try
    {
        SomeOperationBase();
    }
    catch(Exception)
    {
        // Recover your data here.
        // You can throw your own exception here (don't forget to set InnerException for it).
        // Or you can simply rethrow exception.
        throw;
    }
}

protected virtual void SomeOperationBase()
{
    // Your code for SomeOperation() here.
}

The unfortunate side effect is: it seems there are no simple way to have all user code run at the begining or at the end of the code.

void ActionImpl() { /* ... */ }

protected void Action(TextElement aParent)
{
   foreach(TextElement child in this)
       child.Action(); // exception might happen in child too
   ActionImpl();
   NotifyAction(this); // <= potential user exception here
}
protected virtual void NotifyAction(TextElement aParent)
{
   // nothing, up to the subclass
   // the subclass might throw an exception
}

protected void BigAction()
{
    Action_1(); // subclass exception might happen here
    Action_2(); // subclass exception might happen here too
}

private void FillListBox()
{
    foreach (TreeNode rootNode in treeView.Nodes)
    {
        AddSubtree(rootNode, string.Empty);
    }
}
<p/>
private void AddSubtree(TreeNode node, string prefix)
{
    listBox.Items.Add(prefix + node.Text);
    prefix += '>';

    foreach (TreeNode childNode in node.Nodes)
    {
        AddSubtree(childNode, prefix);
    }
}