如何从控件集合中检索具有特定属性的控件？

Question

I create a menu application in an ASP.NET app like this:

// HTML
<td runat="server" id="container">

// C#. This logic is creating
// within a LOOP
Label l = new Label("name_blabla");
Panel p = new Panel();
p.Add(l);
container.Controls.Add(p);

At a given moment I assing the CSS class myclass to the label l :

l.CssClass="myClass";

So the container has only one panel containing only one label with this myclass name assigned.

The purpose is to get this panel from the container once all controls are inserted. I don't know the position where it is inserted. Better with LINQ.

Answer 1

You can use OfType<>() to filter panels, then apply SelectMany() to project the labels inside your panels, then Where() to check the CSS classes of the labels:

Label theLabel
    = container.Controls.OfType<Panel>()
                        .SelectMany(panel => panel.Controls.OfType<Label>())
                        .Where(label => label.CssClass == "MyClass")
                        .FirstOrDefault();

EDIT: If you want to match the panel instead of the label, you can use Any() :

Panel thePanel
    = container.Controls.OfType<Panel>()
                        .Where(panel => panel.Controls.OfType<Label>().Any(
                            label => label.CssClass == "MyClass"))
                        .FirstOrDefault();