Mixing Generics in Collections

I’ve been heavily working with generics over the past few weeks for the final re-factor of LiveFlex. Generics are fantastic but they do have some annoying limitations. You can’t, for instance, create a List<T> and add mixed types such as Item<String>, Item<int> as they are created as seperate classes.

To get around this issue you have to create a common interface or class which kinda misses the point. I’m using generics so we don’t have to cast the objects passed to the rules.

This is how I managed to mix the generic types in the property validation rules.

/// <summary>
/// Wrapper class so we can store different generic instances in a collection
/// </summary>
public abstract class PropertyRule
{
	public abstract bool Check();
}

public class PropertyRule<T, U> : PropertyRule
{
	public override bool Check()
	{
		U val = GetValue(PropertyName);
		return CheckMethod.Invoke(val);
	}
}

List<PropertyRule> RuleList = new List<PropertyRule>();
PropertyRule<ExampleObject, String> ValidEmail= new PropertyRule<ExampleObject, string>(o, "PropTwo", IsEmail);
PropertyRule<ExampleObject, String> stringnotempty = new PropertyRule<ExampleObject, string>(o, "PropTwo", delegate(String val) { return val.IsNotEmpty(); });
foreach(PropertyRule n in RuleList)
{
       Response.Write(Reflection.GetName(() => n) + "=" + n.Check() + "<br/>");
}