Type.IsGenericTypeDefinition Property

Property Value

Type: System.Boolean
true if the Type object represents a generic type definition; otherwise, false.

Imports System.Reflection
Imports System.Collections.Generic

Public Class Example
   Private Shared Sub DisplayGenericTypeInfo(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal t As Type)
      outputBlock.Text &= vbCrLf & t.ToString() & vbCrLf

      outputBlock.Text &= vbTab & "Is this a generic type definition? " _
          & t.IsGenericTypeDefinition & vbCrLf

      outputBlock.Text &= vbTab & "Is it a generic type? " _
          & t.IsGenericType & vbCrLf

      If t.IsGenericType Then
         ' If this is a generic type, display the type arguments.
         '
         Dim typeArguments As Type() = t.GetGenericArguments()

         outputBlock.Text &= vbTab & "List type arguments (" _
             & typeArguments.Length & "):" & vbCrLf

         For Each tParam As Type In typeArguments
            ' If this is a type parameter, display its position.
            '
            If tParam.IsGenericParameter Then
               outputBlock.Text &= vbTab & vbTab & tParam.ToString() _
                   & vbTab & "(unassigned - parameter position " _
                   & tParam.GenericParameterPosition & ")"
            Else
               outputBlock.Text &= vbTab & vbTab & tParam.ToString() & vbCrLf
            End If
         Next tParam
      End If

   End Sub


   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      outputBlock.Text &= String.Format(vbCrLf & "--- Display information about a constructed type, its") & vbCrLf
      outputBlock.Text &= String.Format("    generic type definition, and an ordinary type.") & vbCrLf

      ' Create a Dictionary of Example objects, using strings for the
      ' keys.       
      Dim d As New Dictionary(Of String, Example)()

      DisplayGenericTypeInfo(outputBlock, d.GetType())
      DisplayGenericTypeInfo(outputBlock, d.GetType().GetGenericTypeDefinition())

      ' Display information for an ordinary type.
      DisplayGenericTypeInfo(outputBlock, GetType(String))

   End Sub 'Main
End Class 'Test

' 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 Example
{
   private static void DisplayGenericTypeInfo(System.Windows.Controls.TextBlock outputBlock, Type t)
   {
      outputBlock.Text += String.Format("\r\n{0}", t) + "\n";

      outputBlock.Text += String.Format("\tIs this a generic type definition? {0}",
          t.IsGenericTypeDefinition) + "\n";

      outputBlock.Text += String.Format("\tIs it a generic type? {0}",
          t.IsGenericType) + "\n";

      if (t.IsGenericType)
      {
         // If this is a generic type, display the type arguments.
         //
         Type[] typeArguments = t.GetGenericArguments();

         outputBlock.Text += String.Format("\tList type arguments ({0}):",
             typeArguments.Length) + "\n";

         foreach (Type tParam in typeArguments)
         {
            // If this is a type parameter, display its
            // position.
            //
            if (tParam.IsGenericParameter)
            {
               outputBlock.Text += String.Format("\t\t{0}\t(unassigned - parameter position {1})",
                   tParam,
                   tParam.GenericParameterPosition) + "\n";
            }
            else
            {
               outputBlock.Text += String.Format("\t\t{0}", tParam) + "\n";
            }
         }
      }
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      outputBlock.Text += String.Format("\r\n--- Display information about a constructed type, its") + "\n";
      outputBlock.Text += String.Format("    generic type definition, and an ordinary type.") + "\n";

      // Create a Dictionary of Example objects, using strings for the
      // keys.       
      Dictionary<string, Example> d = new Dictionary<string, Example>();

      // Display information for the constructed type and its generic
      // type definition.
      DisplayGenericTypeInfo(outputBlock, d.GetType());
      DisplayGenericTypeInfo(outputBlock, d.GetType().GetGenericTypeDefinition());

      // Display information for an ordinary type.
      DisplayGenericTypeInfo(outputBlock, 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
 */