Passing int list as a parameter to a web user control

Question

I want to pass an int list (List) as a declarative property to a web user control like this:

Answer 1

After hooking a debugger into Cassini, I see that the null ref is actually coming from System.Web.Compilation.CodeDomUtility.GenerateExpressionForValue, which is basically trying to get an expression for the int[] array you pass into the List constructor. Since there's no type descriptor for the int[] array, it fails (and throws a null ref in the process, instead of the "can't generate property set exception" that it should).

I can't figure out a built in way of getting a serializable value into a List<int>, so I just used a static method:

class IntListConverter : TypeConverter {
    public static List<int> FromString(string value) {
       return new List<int>(
          value
           .Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
           .Select(s => Convert.ToInt32(s))
       );
    }

    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType) {
        if (destinationType == typeof(InstanceDescriptor)) {
            List<int> list = (List<int>)value;
            return new InstanceDescriptor(this.GetType().GetMethod("FromString"),
                new object[] { string.Join(",", list.Select(i => i.ToString()).ToArray()) }
            );
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}

Answer 2

I solved something simular by creating 2 properties:

public List<int> ModuleIDs { get .... set ... }
public string ModuleIDstring { get ... set ... }

The ModuleIDstring converts its value set to a list and sets the ModuleIDs property.

This will also make the ModuleIDs usable from a PropertyGrid etc.

Ok, not the best, typesafe solution, but for me it works.