<SubsetCallableExcludeMemberAttribute(SubsetCallableExcludeMemberType.InterfaceType)> _
Public Shared Function GetUsages ( _
    contentType As SPContentType _
) As IList(Of SPContentTypeUsage)

Dim contentType As SPContentType
Dim returnValue As IList(Of SPContentTypeUsage)

returnValue = SPContentTypeUsage.GetUsages(contentType)

[SubsetCallableExcludeMemberAttribute(SubsetCallableExcludeMemberType.InterfaceType)]
public static IList<SPContentTypeUsage> GetUsages(
    SPContentType contentType
)

Imports System
Imports System.Collections.Generic
Imports Microsoft.SharePoint

Module ConsoleApp
   Sub Main()
      Using siteCollection As SPSite = New SPSite("http://localhost")
         Using rootWeb As SPWeb = siteCollection.RootWeb

            ' Get the content type.
            Dim contentType As SPContentType = _
               rootWeb.AvailableContentTypes(SPBuiltInContentTypeId.Item)

            'Get the usage collection.
            Dim usages As IList(Of SPContentTypeUsage) = _
               SPContentTypeUsage.GetUsages(contentType)

            ' Count the site and list types.
            Dim listTypes As Integer = 0
            Dim siteTypes As Integer = 0
            For Each usage As SPContentTypeUsage In usages
               If usage.IsUrlToList Then
                  listTypes += 1
               Else
                  siteTypes += 1
               End If
            Next usage

            Console.Write("The content type is inherited by {0} site content types", siteTypes)
            Console.WriteLine(" and {0} list content types.", listTypes)

         End Using
      End Using
      Console.Write(vbCrLf + "Press ENTER to continue...")
      Console.ReadLine()
   End Sub

End Module

using System;
using System.Collections.Generic;
using Microsoft.SharePoint;

namespace Test
{
   class ConsoleApp
   {
      static void Main(string[] args)
      {
         using (SPSite siteCollection = new SPSite("http://localhost"))
         {
            using (SPWeb rootWeb = siteCollection.RootWeb)
            {
               // Get the content type.
               SPContentType contentType =
                  rootWeb.AvailableContentTypes[SPBuiltInContentTypeId.Item];

               //Get the usage collection.
               IList<SPContentTypeUsage> usages = SPContentTypeUsage.GetUsages(contentType);

               // Count the site and list types.
               int listTypes = 0;
               int siteTypes = 0;
               foreach (SPContentTypeUsage usage in usages)
               {
                  if (usage.IsUrlToList)
                     listTypes++;
                  else
                     siteTypes++;
               }

               Console.Write("The content type is inherited by {0} site content types", siteTypes);
               Console.WriteLine(" and {0} list content types.", listTypes);
            }
         }
         Console.Write("\nPress ENTER to continue...");
         Console.ReadLine();
      }
   }
}

The content type is inherited by 33 site content types and 20 list content types.

Press ENTER to continue...