C# instantiate generic List from reflected Type [d

问题:

This question already has an answer here:

• Pass An Instantiated System.Type as a Type Parameter for a Generic Class 5 answers

Is it possible to create a generic object from a reflected type in C# (.Net 2.0)?

void foobar(Type t){
    IList<t> newList = new List<t>(); //this doesn't work
    //...
}

The Type, t, is not known until runtime.

回答1:

Try this:

void foobar(Type t)
{
    var listType = typeof(List<>);
    var constructedListType = listType.MakeGenericType(t);

    var instance = Activator.CreateInstance(constructedListType);
}

Now what to do with instance? Since you don't know the type of your list's contents, probably the best thing you could do would be to cast instance as an IList so that you could have something other than just an object:

// Now you have a list - it isn't strongly typed but at least you
// can work with it and use it to some degree.
var instance = (IList)Activator.CreateInstance(constructedListType);

回答2:

static void Main(string[] args)
{
  IList list = foobar(typeof(string));
  list.Add("foo");
  list.Add("bar");
  foreach (string s in list)
    Console.WriteLine(s);
  Console.ReadKey();
}

private static IList foobar(Type t)
{
  var listType = typeof(List<>);
  var constructedListType = listType.MakeGenericType(t);
  var instance = Activator.CreateInstance(constructedListType);
  return (IList)instance;
}

回答3:

You can use MakeGenericType for such operations.

For documentation, see here and here.