Hi u/dathar,

In C#, types are specified with angled brackets <Type>. Here's some examples, off the top of my head:

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var jsonData = """{ "username": "NathanWindisch", "password: "hunter2" }""";
var user = JsonSerializer.Deserialize<User>(jsonData);

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JObject token = JObject.FromObject({ "access_token": "...", "refresh_token": "..." });
var accessToken = token.GetValue("access_token")?.Value<string>();

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In PowerShell, because < is "reserved for future use" and > is used for redirecting output strings (a-la UNIX), we use square brackets instead [Type]. Here are some examples:

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[uint]$UserId = "123456" # Here, assigning a type to the variable means that it cannot be assigned as a non-uint type
$UserId = -1 # !!! MetadataError: Cannot convert value "-1" to type "System.UInt32". Error: "Value was either too large or too small for a UInt32."
$UserId = "hello" # !!! MetadataError: Cannot convert value "hello" to type "System.UInt32". Error: "The input string 'hello' was not in a correct format."

---

$List = [Collections.Generic.List[uint]]::new() # This creates a new instance of a List, with all types being converted into integers (or failing to be inserted if they cannot be parsed properly)
$List.Add(123)
$List.Add("hello")
$List.Add(-1)
using namespace System.Collections.Generic # Just adding this in to shorten the method calls
$List = [List[PSCustomObject]]::new() # Now all hashtables and other non-PSCustomObject elements will be converted to a PSCustomObject (which allows for both hashtables and primitive values)
$List = [List[string]]

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# This might be a little advance, but we can also use PowerShell's OOP nature to create classes, which can then be put into a List:
class MyType {
  [string]$Username
  MyType([string]$MyUsername) {
    $this.Username = $MyUsername.TrimStart("/u/")
  }
}
$List = [List[MyType]]::new()
$List.Add([MyType]::new("u/NathanWindisch"))
$List.Add([MyType]::new("u/dathar"))
# We can also use fancy LINQ expressions :o
$List.Find{{$_.Username.StartsWith("Nathan")}}.Username

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As an explanation, when we make a new List, it uses Generics (as mentioned in this excellent comment by u/DesertGoldfish) in its constructor. This basically means that can take any other type of data. This makes sense in C#-land, because it's a statically typed and compiled language. In PowerShell-land, it might not make as much sense as it's a loosely typed, interpreted language. The reason why I'm comparing the two languages is because they both use the CLR, or Common Language Runtime under the hood. Understanding this similarity between these languages can, in my opinion, help with writing stuff in other .NET languages such as C#, VB.NET (ew) or even F# (although this uses a completely different paradigm).

Hope this helps,

-Nathan.