Can I have a method returning IEnumerator<T> and use it in a foreach loop?

Can I have a method returning IEnumerator<T> and use it in a foreach loop?

"I need to set the height of every textbox on my form, some of which are nested within other controls. I thought I could do something like this:

private static IEnumerator<TextBox> FindTextBoxes(Control rootControl)
{
foreach (Control control in rootControl.Controls)
{
if (control.Controls.Count > 0)
{
// Recursively search for any TextBoxes within each child control
foreach (TextBox textBox in FindTextBoxes(control))
{
yield return textBox;
}
}

TextBox textBox2 = control as TextBox;
if (textBox2 != null)
{
yield return textBox2;
}
}
}

Using it like this:

foreach(TextBox textBox in FindTextBoxes(this))
{
textBox.Height = height;
}

But of course the compiler spits its dummy, because foreach expects an IEnumerable rather than an IEnumerator.

Is there a way to do this without having to create a separate class with a GetEnumerator() method?"

Asked by: Guest | Views: 312

Total answers/comments: 4

Comments display order:

Guest [Entry]

As the compiler is telling you, you need to change your return type to IEnumerable. That is how the yield return syntax works.

Guest [Entry]

"Just to clarify

private static IEnumerator<TextBox> FindTextBoxes(Control rootControl)

Changes to

private static IEnumerable<TextBox> FindTextBoxes(Control rootControl)

That should be all :-)"

Guest [Entry]

If you return IEnumerator, it will be a different enumerator object each time call that method (acting as though you reset the enumerator on each iteration). If you return IEnumerable then a foreach can enumerate based on the method with the yield statement.

Guest [Entry]

"// Generic function that gets all child controls of a certain type,
// returned in a List collection
private static List<T> GetChildTextBoxes<T>(Control ctrl) where T : Control{
List<T> tbs = new List<T>();
foreach (Control c in ctrl.Controls) {
// If c is of type T, add it to the collection
if (c is T) {
tbs.Add((T)c);
}
}
return tbs;
}

private static void SetChildTextBoxesHeight(Control ctrl, int height) {
foreach (TextBox t in GetChildTextBoxes<TextBox>(ctrl)) {
t.Height = height;
}
}"