How do I create an instance of the Array type with a given ElementType?

Question

How do I create a type object that represents the type of an array with a given element type?

Type t = MakeArrayType(elementType);  // How?

Such that

Assert(t.GetElementType() == elementType);

I can create a dummy instance of my requested array and then get the type from there. But I wonder if there is a way to get the type without creating the instance first?

object myArrayInstance = Array.CreateInstance(elementType, 0);
Type t = myArrayInstance.GetType();   // This is the desired type.

Jon Skeet · Accepted Answer · 2011-08-07 11:22:49Z

4

If t refers to a Type, then t.GetType() will obviously be typeof(Type) or a subtype - not typeof(Array).

However, I suspect you want Type.MakeArrayType:

Type arrayType = elementType.MakeArrayType();

answered Aug 7, 2011 at 11:22

Jon Skeet

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4 Comments

Anders Forsgren Over a year ago

Thanks Jon, I edited the question too (t.GetType() -> just t). I don't know why I didn't think of going "backwards" rather than starting at typeof(Array).

Jon Skeet Over a year ago

@Anders: You still won't get t == typeof(Array) - if that worked, you could just use typeof(Array) to start with :) You'll get a t which is assignment-compatible with Array though.

Anders Forsgren Over a year ago

Ok, thanks. Just out of curiosity (I'll change the question so it mathes the answer later), how would a proper assert in the question look really? Simply Assert(t.IsArray()) perhaps? or did that assert not help the question at all :) ?

Jon Skeet Over a year ago

t.IsArray would work, yes. Or typeof(Array).IsAssignableFrom(t)

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