Type.IsGenericTypeDefinition Property
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Gets a value indicating whether the current Type represents a generic type definition, from which other generic types can be constructed.
public:
virtual property bool IsGenericTypeDefinition { bool get(); };public virtual bool IsGenericTypeDefinition { get; }member this.IsGenericTypeDefinition : boolPublic Overridable ReadOnly Property IsGenericTypeDefinition As BooleanProperty Value
true if the Type object represents a generic type definition; otherwise, false.
Examples
The following example displays information about a type, including whether or not it's a generic type definition. Information is displayed for a constructed type, for its generic type definition, and for an ordinary type.
using namespace System;
using namespace System::Reflection;
using namespace System::Collections::Generic;
public ref class Test
{
private:
static void DisplayGenericTypeInfo( Type^ t )
{
Console::WriteLine( L"\r\n{0}", t );
Console::WriteLine( L"\tIs this a generic type definition? {0}",
t->IsGenericTypeDefinition );
Console::WriteLine( L"\tIs it a generic type? {0}",
t->IsGenericType );
if ( t->IsGenericType )
{
// If this is a generic type, display the type arguments.
//
array<Type^>^typeArguments = t->GetGenericArguments();
Console::WriteLine( L"\tList type arguments ({0}):",
typeArguments->Length );
System::Collections::IEnumerator^ myEnum =
typeArguments->GetEnumerator();
while ( myEnum->MoveNext() )
{
Type^ tParam = safe_cast<Type^>(myEnum->Current);
// If this is a type parameter, display its
// position.
//
if ( tParam->IsGenericParameter )
{
Console::WriteLine(
L"\t\t{0}\t(unassigned - parameter position {1})",
tParam, tParam->GenericParameterPosition );
}
else
{
Console::WriteLine( L"\t\t{0}", tParam );
}
}
}
}
public:
static void Main()
{
Console::Write( L"\r\n--- Display information about a " );
Console::WriteLine( L"constructed type, its" );
Console::WriteLine( L" generic type definition, and an ordinary type." );
// Create a Dictionary of Test objects, using strings for the
// keys.
Dictionary< String^,Test^ >^ d = gcnew Dictionary< String^,Test^ >;
// Display information for the constructed type and its generic
// type definition.
DisplayGenericTypeInfo( d->GetType() );
DisplayGenericTypeInfo( d->GetType()->GetGenericTypeDefinition() );
// Display information for an ordinary type.
DisplayGenericTypeInfo( String::typeid );
}
};
int main()
{
Test::Main();
}
/* This example produces the following output:
--- Display information about a constructed type, its
generic type definition, and an ordinary type.
System.Collections.Generic.Dictionary[System.String,Test]
Is this a generic type definition? False
Is it a generic type? True
List type arguments (2):
System.String
Test
System.Collections.Generic.Dictionary[TKey,TValue]
Is this a generic type definition? True
Is it a generic type? True
List type arguments (2):
TKey (unassigned - parameter position 0)
TValue (unassigned - parameter position 1)
System.String
Is this a generic type definition? False
Is it a generic type? False
*/
using System;
using System.Reflection;
using System.Collections.Generic;
public class Test
{
private static void DisplayGenericTypeInfo(Type t)
{
Console.WriteLine("\r\n{0}", t);
Console.WriteLine("\tIs this a generic type definition? {0}",
t.IsGenericTypeDefinition);
Console.WriteLine("\tIs it a generic type? {0}",
t.IsGenericType);
if (t.IsGenericType)
{
// If this is a generic type, display the type arguments.
//
Type[] typeArguments = t.GetGenericArguments();
Console.WriteLine("\tList type arguments ({0}):",
typeArguments.Length);
foreach (Type tParam in typeArguments)
{
// If this is a type parameter, display its
// position.
//
if (tParam.IsGenericParameter)
{
Console.WriteLine("\t\t{0}\t(unassigned - parameter position {1})",
tParam,
tParam.GenericParameterPosition);
}
else
{
Console.WriteLine("\t\t{0}", tParam);
}
}
}
}
public static void Main()
{
Console.WriteLine("\r\n--- Display information about a constructed type, its");
Console.WriteLine(" generic type definition, and an ordinary type.");
// Create a Dictionary of Test objects, using strings for the
// keys.
Dictionary<string, Test> d = new Dictionary<string, Test>();
// Display information for the constructed type and its generic
// type definition.
DisplayGenericTypeInfo(d.GetType());
DisplayGenericTypeInfo(d.GetType().GetGenericTypeDefinition());
// Display information for an ordinary type.
DisplayGenericTypeInfo(typeof(string));
}
}
/* This example produces the following output:
--- Display information about a constructed type, its
generic type definition, and an ordinary type.
System.Collections.Generic.Dictionary[System.String,Test]
Is this a generic type definition? False
Is it a generic type? True
List type arguments (2):
System.String
Test
System.Collections.Generic.Dictionary[TKey,TValue]
Is this a generic type definition? True
Is it a generic type? True
List type arguments (2):
TKey (unassigned - parameter position 0)
TValue (unassigned - parameter position 1)
System.String
Is this a generic type definition? False
Is it a generic type? False
*/
open System
open System.Collections.Generic
type Test() = class end
let displayGenericTypeInfo (t: Type) =
printfn $"\n{t}"
printfn $"\tIs this a generic type definition? {t.IsGenericTypeDefinition}"
printfn $"\tIs it a generic type? {t.IsGenericType}"
if t.IsGenericType then
// If this is a generic type, display the type arguments.
let typeArguments = t.GetGenericArguments()
printfn $"\tList type arguments ({typeArguments.Length}):"
for tParam in typeArguments do
// If this is a type parameter, display its
// position.
if tParam.IsGenericParameter then
printfn $"\t\t{tParam}\t(unassigned - parameter position {tParam.GenericParameterPosition})"
else
printfn $"\t\t{tParam}"
printfn "\r\n--- Display information about a constructed type, its"
printfn " generic type definition, and an ordinary type."
// Create a Dictionary of Test objects, using strings for the keys.
let d = Dictionary<string, Test>()
// Display information for the constructed type and its generic
// type definition.
displayGenericTypeInfo (d.GetType())
displayGenericTypeInfo (d.GetType().GetGenericTypeDefinition())
// Display information for an ordinary type.
displayGenericTypeInfo typeof<string>
(* This example produces the following output:
--- Display information about a constructed type, its
generic type definition, and an ordinary type.
System.Collections.Generic.Dictionary[System.String,Test]
Is this a generic type definition? False
Is it a generic type? True
List type arguments (2):
System.String
Test
System.Collections.Generic.Dictionary[TKey,TValue]
Is this a generic type definition? True
Is it a generic type? True
List type arguments (2):
TKey (unassigned - parameter position 0)
TValue (unassigned - parameter position 1)
System.String
Is this a generic type definition? False
Is it a generic type? False
*)
Imports System.Reflection
Imports System.Collections.Generic
Public Class Test
Private Shared Sub DisplayGenericTypeInfo(ByVal t As Type)
Console.WriteLine(vbCrLf & t.ToString())
Console.WriteLine(vbTab & "Is this a generic type definition? " _
& t.IsGenericTypeDefinition)
Console.WriteLine(vbTab & "Is it a generic type? " _
& t.IsGenericType)
If t.IsGenericType Then
' If this is a generic type, display the type arguments.
'
Dim typeArguments As Type() = t.GetGenericArguments()
Console.WriteLine(vbTab & "List type arguments (" _
& typeArguments.Length & "):")
For Each tParam As Type In typeArguments
' If this is a type parameter, display its position.
'
If tParam.IsGenericParameter Then
Console.WriteLine(vbTab & vbTab & tParam.ToString() _
& vbTab & "(unassigned - parameter position " _
& tParam.GenericParameterPosition & ")")
Else
Console.WriteLine(vbTab & vbTab & tParam.ToString())
End If
Next tParam
End If
End Sub
Public Shared Sub Main()
Console.WriteLine(vbCrLf & "--- Display information about a constructed type, its")
Console.WriteLine(" generic type definition, and an ordinary type.")
' Create a Dictionary of Test objects, using strings for the
' keys.
Dim d As New Dictionary(Of String, Test)()
DisplayGenericTypeInfo(d.GetType())
DisplayGenericTypeInfo(d.GetType().GetGenericTypeDefinition())
' Display information for an ordinary type.
DisplayGenericTypeInfo(GetType(String))
End Sub
End Class
' This example produces the following output:
'
'--- Display information about a constructed type, its
' generic type definition, and an ordinary type.
'
'System.Collections.Generic.Dictionary[System.String, Test]
' Is this a generic type definition? False
' Is it a generic type? True
' List type arguments (2):
' System.String
' Test
'
'System.Collections.Generic.Dictionary[TKey,TValue]
' Is this a generic type definition? True
' Is it a generic type? True
' List type arguments (2):
' TKey (unassigned - parameter position 0)
' TValue (unassigned - parameter position 1)
'
'System.String
' Is this a generic type definition? False
' Is it a generic type? False
Remarks
A generic type definition is a template from which other types can be constructed. For example, from the generic type definition G<T> (expressed in C# syntax; G(Of T) in Visual Basic or generic <typename T> ref class G in C++) you can construct and instantiate the type G<int> (G(Of Integer) in Visual Basic), by calling the MakeGenericType method with a generic argument list containing the Int32 type. Given a Type object representing this constructed type, the GetGenericTypeDefinition method gets the generic type definition back again.
Use the IsGenericTypeDefinition property to determine whether you can create new types from the current type. If the IsGenericTypeDefinition property returns true, you can call the MakeGenericType method to create new generic types.
For a list of the invariant conditions for terms used in generic reflection, see the IsGenericType property remarks.
Applies to
See also
Collaborate with us on GitHub
The source for this content can be found on GitHub, where you can also create and review issues and pull requests. For more information, see our contributor guide.
