Vlad Hrybok's Tech Notes

I thought I knew ASP.NET. I started ASP.NET programming in 2001, and I started it with customer/server control development and was cranking them out with no problem. So theoretically I should not have struggled for six hours with a CompositeControl not being able to save nested controls' state between postbacks.

All it came down to is calling EnsureChildControls() from the OnInit().

[ToolboxData("<{0}:BogusCustomControl runat=server></{0}:BogusCustomControl>")]
public class BogusCustomControl : CompositeControl
{
    Button btn = new Button();

    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);

        this.EnsureChildControls(); // << This is it! This makes ViewState work for a CompositeControl
    }

    protected override void OnLoad(EventArgs e)
    {
        if (!this.Page.IsPostBack)
        {
            // Set value once to test whether it's preserved between postbacks
            this.btn.Text = DateTime.Now.ToLongTimeString();
        }

        base.OnLoad(e);
    }

    protected override void CreateChildControls()
    {
        this.btn.ID = "whatever";
        this.Controls.Add(this.btn);

        base.CreateChildControls();
    }
}