Accessing properties of different types of UserControls

Question

I created a new Windows Forms Control Library and created 2 different user controls. I imported the controls to my main form on another project and am able to access controls when I create them.

UserControlType1 uc1 = new UserControlType1();
UserControlType2 uc2 = new UserControlType2();

The controls both have a Status property I can access on the form. I can access the status from each individually.

Debug.Print(uc1.Status);
Debug.Print(uc2.Status);

But is there a way I can access that status from an array of different user controls or some other way? I plan on having 2 dozen or more different user controls and would like to reference them by index depending on which tab on the main form is active. I'm new to user controls, what approach should I take?

object[] uc_array = new object[2]{uc1, uc2};  // unable to access properties

user_17322803 · Answer

I ended up creating a support class inherited by all the different usercontrols. In the main form I created a new array of these types and populated them.

UserControlType1 uc1 = new UserControlType1();
UserControlType2 uc2 = new UserControlType2();
Support[] supp_ar = new Support[2]{uc1.Properties, uc2.Properties};

Debug.Print(supp_ar[0].Status);  // does now show the status

user_5438626 · Answer

I'm in agreement with Fildor's comment because implementing an interface can be quite a bit more flexible and extensible. There's no requirement to inherit any particular base class, and it's possible to mix-and-match interfaces as a form of de facto multiple inheritance. In this case, it might be especially useful to include an event so the UserControl can notify the parent when something happens that might require a status update.

interface IStatusProvider
{
    string Status { get; }
    event EventHandler StatusUpdated;
}

Example of a CustomUserControl : UserControl, IStatusProvider

class UserControlTypeA : UserControl, IStatusProvider
{
    public UserControlTypeA()
    {
        _checkBox =
            new CheckBox
            {
                Text = "CheckBox",
                Size = new Size(150, 50),
                TextAlign = ContentAlignment.MiddleCenter,
                Appearance = Appearance.Button,
            };
        _checkBox.CheckedChanged += (sender, e) => 
            StatusUpdated?.Invoke(this, EventArgs.Empty);
        Controls.Add(_checkBox);
        AutoSizeMode = AutoSizeMode.GrowAndShrink;
        AutoSize = true;
    }
    private readonly CheckBox _checkBox;

    public event EventHandler StatusUpdated;

    public string Status => $"{GetType().Name}: {_checkBox.Checked}";
}

The various different UserControl types can be instantiated as a collection of IStatusProvider:

IStatusProvider[] UserControls = new IStatusProvider[]
{
    new UserControlTypeA(),
    new UserControlTypeB(),
    new UserControlTypeC(),
};

You can use an implicit cast in a foreach, for example to use it as a Control:

// Implicit cast from IStatusProvider to Control
foreach (Control control in UserControls)
{
    flowLayoutPanel.Controls.Add(control);
}

Otherwise, the variant in the foreach will evaluate to IStatusProvider and this is where the different user controls will provide different responses to Status:

// IStatusProvider
foreach (var statusProvider in UserControls)
{
    statusProvider.StatusUpdated += onAnyStatusUpdated;
}

private void onAnyStatusUpdated(object sender, EventArgs e)
{
    foreach (var statusProvider in UserControls)
    {
        textBoxMultiline.AppendText($"{statusProvider.Status}{Environment.NewLine}");
    }
    textBoxMultiline.AppendText(Environment.NewLine);
}

The result of iterating the UserControls collection is shown here, where the flowLayoutPanel is on the left and the status updates are shown on the right.

Accessing properties of different types of UserControls

2 Answers