![]() Get a Type object that represents the generic type. To construct an instance of a generic type To do this at run time, using reflection, requires the MakeGenericType method. You cannot create instances of it unless you specify real types for its generic type parameters. ![]() GenericParameterAttributes.NotNullableValueTypeConstraint) ThenĬonsole.WriteLine(" Must be a non-nullable value type.")Ĭonstructing an Instance of a Generic TypeĪ generic type is like a template. GenericParameterAttributes.ReferenceTypeConstraint) ThenĬonsole.WriteLine(" Must be a reference type.") GenericParameterAttributes.DefaultConstructorConstraint) ThenĬonsole.WriteLine(" Must have a parameterless constructor.") If GenericParameterAttributes.None (sConstraints And _ If sConstraints = GenericParameterAttributes.None ThenĬonsole.WriteLine(" No special constraints.") GenericParameterAttributes.NotNullableValueTypeConstraint))Ĭonsole.WriteLine(" Must be a non-nullable value type.") GenericParameterAttributes.ReferenceTypeConstraint))Ĭonsole.WriteLine(" Must be a reference type.") GenericParameterAttributes.DefaultConstructorConstraint))Ĭonsole.WriteLine(" Must have a parameterless constructor.") If (GenericParameterAttributes.None != (sConstraints & If (sConstraints = GenericParameterAttributes.None)Ĭonsole.WriteLine(" No special constraints.") GenericParameterAttributes::NotNullableValueTypeConstraint))Ĭonsole::WriteLine(" Must be a non-nullable value type.") GenericParameterAttributes::ReferenceTypeConstraint))Ĭonsole::WriteLine(" Must be a reference type.") GenericParameterAttributes::DefaultConstructorConstraint))Ĭonsole::WriteLine(" Must have a parameterless constructor.") If (GenericParameterAttributes::None != (sConstraints & if (sConstraints = GenericParameterAttributes::None)Ĭonsole::WriteLine(" No special constraints.") In this case, use GenericParameterAttributes.SpecialConstraintMask to isolate the special constraint flags. Thus, to test for either of these conditions you must use the appropriate mask. The special constraint attributes are flags, and the same flag ( GenericParameterAttributes.None) that represents no special constraints also represents no covariance or contravariance. GenericParameterAttributes.SpecialConstraintMask GenericParameterAttributes.SpecialConstraintMask ĭim sConstraints As GenericParameterAttributes = _ GenericParameterAttributes sConstraints = GenericParameterAttributes::SpecialConstraintMask ![]() ![]() The property also includes values that represent variance, which you can mask off as shown in the following code. Use the GenericParameterAttributes property to discover the special constraints on a type parameter, such as requiring that it be a reference type. Console::WriteLine(" Is this a generic type? ", _Ĭonsole.WriteLine(" Base type constraint: None") Use the IsGenericType property to determine whether the type is generic, and use the IsGenericTypeDefinition property to determine whether the type is a generic type definition. Type^ d1 = Dictionary::typeid ĭim d1 As Type = GetType(Dictionary(Of ,)) Note that in the rest of this procedure, the type is contained in a method parameter named t. See the Type class topic for other ways to get a Type object. In the following code, the type is obtained using the C# typeof operator ( GetType in Visual Basic, typeid in Visual C++). Get an instance of Type that represents the generic type. To examine a generic type and its type parameters You can create a Type object that represents a constructed type by binding type arguments to the type parameters of a generic type definition. The first procedure in this section examines generic types. The principle difference is that a generic type has a list of Type objects representing its generic type parameters. Information about generic types is obtained in the same way as information about other types: by examining a Type object that represents the generic type.
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