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c#asp.netwebformspropertiesmarkup

Is it possible to initialize a Control's List<T> property in markup?


Let's say we have the following:

public enum RenderBehaviors
{
    A,
    B,
    C,
}

public class MyControl : Control
{
    public List<RenderBehaviors> Behaviors { get; set; }

    protected override void Render(HtmlTextWriter writer)
    {
        // output different markup based on behaviors that are set
    }
}

Is it possible to initialize the Behaviors property in the ASPX/ASCX markup? i.e.:

<ns:MyControl runat="server" ID="ctl1" Behaviors="A,B,C" />

Subclassing is not an option in this case (the actual intent of the Behaviors is slightly different than this example). WebForms generates a parser error when I try to initialize the property in this way. The same question could be applied to other List types (int, strings).


Solution

  • After researching this further, I found that WebForms does use a TypeConverter if it can find it. The type or the property needs to be decorated properly, as detailed in this related question.

    I wound up implementing something similar to this:

    public class MyControl : Control
    {
        private readonly HashSet<RenderBehaviors> coll = new HashSet<RenderBehaviors>();
    
        public IEnumerable<RenderBehaviors> Behaviors { get { return coll; } }
    
        public string BehaviorsList
        {
            get { return string.Join(',', coll.Select(b => b.ToString()).ToArray()); }
            set
            {
                coll.Clear();
                foreach (var b in value.Split(',')
                    .Select(s => (RenderBehvaior)Enum.Parse(typeof(RenderBehavior), s)))
                {
                    coll.Add(b);
                }
            }
        }
    }