GenericParameterAttributes Enumeration

 

Describes the constraints on a generic type parameter of a generic type or method.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

Namespace:   System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[<FlagsAttribute>]
type GenericParameterAttributes

Member nameDescription
Contravariant

The generic type parameter is contravariant. A contravariant type parameter can appear as a parameter type in method signatures.

Covariant

The generic type parameter is covariant. A covariant type parameter can appear as the result type of a method, the type of a read-only field, a declared base type, or an implemented interface.

DefaultConstructorConstraint

A type can be substituted for the generic type parameter only if it has a parameterless constructor.

None

There are no special flags.

NotNullableValueTypeConstraint

A type can be substituted for the generic type parameter only if it is a value type and is not nullable.

ReferenceTypeConstraint

A type can be substituted for the generic type parameter only if it is a reference type.

SpecialConstraintMask

Selects the combination of all special constraint flags. This value is the result of using logical OR to combine the following flags: DefaultConstructorConstraint, ReferenceTypeConstraint, and NotNullableValueTypeConstraint.

VarianceMask

Selects the combination of all variance flags. This value is the result of using logical OR to combine the following flags: Contravariant and Covariant.

The members of the GenericParameterAttributes enumeration are divided into two groups, the variance group and the special constraints group. To test a GenericParameterAttributes value for variance flags, first perform a bitwise AND operation with VarianceMask. If the result is None, there are no variance flags. Similarly, use SpecialConstraintMask to test for constraint flags.

The following code example defines a generic type Test with two type parameters. The second type parameter has a base class constraint and a reference type constraint. When the program executes, the constraints are examined using the Type.GenericParameterAttributes property and the Type.GetGenericParameterConstraints method.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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