I want a Master UserControl (a Master page, but for UserControls)

Question

ASP.NET master pages - essential things.

However, I have a lot of very similar UserControls in my projects - it might be a standard layout for an AJAX ModalPopup, or something more involved.

I wish I could get rid of some of my duplicated code (both in ascx files and code-behind) with some Master UserControls.

Does anyone have any suggestions of a way to achieve this?

Answer 1

Inheritance. You build the base control as a base class, and then inherit from it.

Answer 2

You could also place nested user control on a place holder control in a "master" user control. Use Load method that accepts virtual path to ascx file to load appropriate control.

Answer 3

The closest thing I can suggest for what you are looking for is a templated custom control. Unfortunately, sharing controls across projects is a lot easier if those things are custom controls, without an ascx file.

Answer 4

I managed to get this to work using the following code:

public class MasterLoader : UserControl
{
    MasterUserControl _masterUserControl;

    protected override void CreateChildControls()
    {
        Controls.Clear();
        base.CreateChildControls();

        Controls.Add(MasterControl);
    }

    protected override void AddedControl(Control control, int index)
    {
        if (control is MasterUserControl)
            base.AddedControl(control, index);
        else
            MasterControl.ContentArea.Controls.Add(control);
    }

    private MasterUserControl MasterControl
    {
        get
        {
            if (_masterUserControl== null)
                _masterUserControl= (MasterUserControl)LoadControl("~/MasterUserControl.ascx");

            return _masterUserControl;
        }
    }
}

Child user controls inherit from the MasterLoader class. The master user control included a placeholder control that I exposed as a public property called ContentArea.

public partial class MasterUserControl: UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    public PlaceHolder ContentArea 
    {
        get
        {
            return phContent;
        }
    }
}

Event binding and view state work as expected without any changes to any of the user controls.