How to get type of T generic?

Question

Here is signature of the function:

public static T[] Shuffle<T>(T[] array)

Inside the function I want to check the type:

var t = T.GetType();

But I get this error:

'T' is a type parameter, which is not valid in the given context

Any idea why I get error and how to get type of T?

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/typeof — Waayd, Jul 28 '18 at 14:39
GetType() is only valid on an object. T is not an object, it is a type. Simply use typeof(T). Do beware it is a smell, code that needs it is rarely generic code. — Hans Passant, Jul 28 '18 at 15:01

score 3 · Accepted Answer · answered Jul 28 '18 at 14:33

3

You can use typeof to get the type of a generic parameter: typeof(T)

answered Jul 28 '18 at 14:33

Selman Genç

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Thanks for post.Any idea can I check if T is value type for example int? – Michael Jul 28 '18 at 14:36
you try this; "typeof(T) is int" it will return bool result – Waayd Jul 28 '18 at 14:42
1

@Waay: `typeof(T) is Type`! but `typeof(T) == typeof(int)` is true. – Olivier Jacot-Descombes Jul 28 '18 at 14:48
@Michael `typeof(T).IsValueType` – Selman Genç Jul 28 '18 at 14:53
@OlivierJacot-Descombes yes right – Waayd Jul 28 '18 at 14:57

Olivier Jacot-Descombes · Answer 2 · 2023-05-11T13:34:48.153

On type names and generic type parameter names given as a C# identifier you can apply the typeof operator

Type type = typeof(T);

on objects you can call the GetType method.

Type arrayType = array.GetType();
Type elementType = arrayType.GetElementType();

Note that typeof yields the static type known at compile time, where as GetType yields the dynamic type at runtime.

object obj = new Person();
Type staticType = typeof(object); // ==> System.Object
Type runtimeType = obj.GetType(); // ==> Person

Since typeof(T) yields an object of type System.Type, you can test for a type with

typeof(T) == typeof(Person)

or

T is Person

however; these two comparisons are not equivalent. If you have

class Student : Person
{ }

And assuming that T is of type Student, then

typeof(T) == typeof(Person)      ===> false, because it is typeof(Student)
T is Person                      ===> true, because every type inheriting Person is a Person

The first comparison yields false, because we test for equality of the two Type objects that are different.

How to get type of T generic?

2 Answers2