This article is a simple column of some generic reflection techniques, preparing for future articles.
1. How to get a TYPE object of a closed constructed type?
It is assumed that the following types:
Class
TestType
<
T
>
Class
TestType
<
T, U
>
If you want to get a TYPE object that is closed, you only need to use the C # TypeOf operator, or the VB's GetType operator can act on the specific type:
//
C #
Type T1
=
Typeof
(TestType
<
int
>
);
'
VB
DIM
T2
AS
Type
=
Gettype
(TestType
String
))
2. How do I get a generic type? TYPE object?
The so-called generic type is a type of parameters, but the type parameters have not yet specified original definitions. We cannot use TestType
Type T1
=
Typeof
(TestType
<>
); TYPE T2
=
Typeof
(TestType
<
,
>
);
DIM
T1, T2
AS
Typet1
=
Gettype
(TESTTYPE (OF)) T2
=
Gettype
(TESTTTYPE (OF,))
Note that we can use a comma to distinguish the number of type parameters. This shows that the generic type can only be overloaded by the type parameters, regardless of what constraints. The TYPE obtained here is the generic type of type parameters.
3. How to generate a generic type TYPE object from the TYPE object of the constructor?
The new method of the Type class can do it.
//
C #
Type CT
=
Typeof
(List)
<
int
>
);
//
Get Generic Type Definition
Type gt
=
Ct.getGenericTyPedefinition ();
4. How do I get the TYPE object for type parameters?
The generic type T, U and other types of parameters, and the actual values in the run are available from the TYPE object.
'
VB
DIM
t
AS
Type
=
Gettype
(List
Integer
))
'
Get the generic arguments, an array
DIM
Typeargs
AS
TYPE ()
=
T.GetGenericarguments ()
'
Get the first argument: Integer in this case
DIM
Targ0
AS
Type
=
Typeargs
0
)
5, generate Type objects of the constructed type from the generic type Type object.
It is usually used to generate another constructical type from a construction type.
//
C #
Type CT
=
Typeof
(List)
<
int
>
Type GT
=
Ct.getGenericTyPedefinition ();
//
Make Another Constructed Type
//
The List
Type CT2
=
gt.makegenerictype (Typeof
(
String
));
6, how to take an open constructive type (Open constructed type) TYPE object?
Open consigne is one of the most difficult processes because their type parameters have been specified, but not specified as specific types, but specified as type parameters for other generic types. This type is especially important when performing reflection overload selection and reflection emit. Our method is to get the type of type parameters from the definition of the host generic type, and then build an open consignment type. Here, we get the parameters of the constructor of the list
'
The Generic Type of List (of t)
DIM
TLIST
AS
Type
=
Gettype
(List (of))
'
Get the "t" of list (of t)
DIM
TypeParam
AS
Type
=
TList.GetGenericarguments () ()
0
)
'
The Generic Type of Ienumerable (of t)
DIM
Tienum
AS
Type
=
Gettype
(IEnumerable (OF))
'
Make the Open Constructed Type
DIM
Tienumopen
AS
Type
=
Tienum.makegenericType (TypeParam)
'
Only use this method to achieve open constructive type
'
You can use this syntax to get the truly desired constructor definition
'
IENUMERABLE (OF T) is an open consignment type in the definition of constructor
DIM
c
AS
Constructorinfo
=
_ TList.getConstructor (
New
Type () {tienumopen})
