How to find all objects that implement a interface and invoke a method

Question

I have a UserControl that have a few child UserControl's and those UserControl's have child UserControl's.

Consider this:

MainUserControl
  TabControl
    TabItem
      UserControl
        UserControl
          UserControl : ISomeInterface
    TabItem
      UserControl
        UserControl
          UserControl : ISomeInterface
    TabItem
      UserControl
        UserControl
          UserControl : ISomeInterface
    TabItem
      UserControl
        UserControl
          UserControl : ISomeInterface

This is what i have so far, but finds no ISomeInterface:

PropertyInfo[] properties = MainUserControl.GetType().GetProperties();
foreach (PropertyInfo property in properties)
{
    if (typeof(ISomeInterface).IsAssignableFrom(property.PropertyType))
    {
        property.GetType().InvokeMember("SomeMethod", BindingFlags.InvokeMethod, null, null, null);
    }
}

Is it possible so find all the child UserControl's from MainUserControl that implement ISomeInterface via reflection and call a method(void SomeMethod()) on that interface?

Why do you think GetProperties() method would go down recursively? You are enumerating the properties of the type, not the whole controls hierarchy. Consider enumerating Controls collection instead. — Alexander Tsvetkov, Apr 01 '13 at 10:04

Matthew Watson · Accepted Answer · 2013-04-01T10:24:24.677

You will need to recursively iterate through all the subcontrols within your MainUserControl.

Here's a helper method you can use:

/// <summary>
/// Recursively lists all controls under a specified parent control.
/// Child controls are listed before their parents.
/// </summary>
/// <param name="parent">The control for which all child controls are returned</param>
/// <returns>Returns a sequence of all controls on the control or any of its children.</returns>

public static IEnumerable<Control> AllControls(Control parent)
{
    if (parent == null)
    {
        throw new ArgumentNullException("parent");
    }

    foreach (Control control in parent.Controls)
    {
        foreach (Control child in AllControls(control))
        {
            yield return child;
        }

        yield return control;
    }
}

Then:

foreach (var control in AllControls(MainUserControl))
{
    PropertyInfo[] properties = control.GetType().GetProperties();
    ... Your loop iterating over properties

Or (much better if this will work for you, since it's a lot simpler):

foreach (var control in AllControls(MainUserControl))
{
    var someInterface = control as ISomeInterface;

    if (someInterface != null)
    {
        someInterface.SomeMethod();
    }
}

Or, using Linq (need a using System.Linq to do this):

foreach (var control in AllControls(MainUserControl).OfType<ISomeInterface>())
    control.SomeMethod();

Which seems best of all. :)

Maybe you could add using the `is` operator. OP seems to be in the direction of using reflection while dynamic casting is much easier (and cheaper) (or am I missing something too?) — bas, Apr 01 '13 at 10:10
Yeah, that was what I meant. Already upvoted but imaginary +2 then :) — bas, Apr 01 '13 at 10:17
System.Windows.Controls.Control doesn't have a Controls property?! — Diego Frehner, Jun 18 '13 at 14:09
@DiegoFrehner You are correct - `.Controls` is for `Windows.Forms.Control`! For WPF we'd need to use VisualTreeHelper [as described here](http://stackoverflow.com/questions/14875042/finding-all-child-controls-wpf). I'm not sure why the OP didn't say anything about that... — Matthew Watson, Jun 18 '13 at 14:38

score 3 · Answer 2 · answered Apr 01 '13 at 10:15

3

Maybe I am looking in the wrong direction myself. What I meant with the comment on Matthews answer was:

 foreach (var control in AllControls(MainUserControl))
 {
     if (control is ISomeInterface)
     {

     }
 }

or

 foreach (var control in AllControls(MainUserControl))
 {
     var someInterface = control as ISomeInterface;
     if (someInterface != null)
     {
          someInterface.SomeMethod();
     }
 }

answered Apr 01 '13 at 10:15

bas

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1

Agreed, I added it per your suggestion. :) – Matthew Watson Apr 01 '13 at 10:16

How to find all objects that implement a interface and invoke a method

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