Here's the simplest possible code for creating a custom collection class in the Microsoft .NET Framework that includes support for For…Each loops, an indexer method and initializing collections with { ...

If you like the idea of creating a new class from whatever other classes you have lying around, you have two ways of doing in TypeScript ... and both are type safe (within limits).

Here is the magic spell you need: Create a Class Library project in your solution in the supported language of your choice. I like C#, but Visual Basic .NET also works.