I am trying to implement a system where I need to have a C# class with property which type can be one of types.

In F# this features called “Discriminated Unions”, in TypeScript it is called “Union Types”.

Here is an example of how I could implement it in TypeScript:

class Something {
    public myField?: boolean | Date;
}

let something = new Something();

something.myField = true;
something.myField = new Date();

As far as I know it’s not possible in C#. What are the workarounds?

How would you (as C# developer) implement this?

Options I considered

1. Using object type might work in my case but I would like to have more precise solution.

2. I’ve also tried to use implicit conversion but it looks too hacky

class MyFieldType {
  private bool _valueBool;
  private DateTime _valueDateTime;

   public MyFieldType(DateTime value) {
    _valueDateTime = value;
  }
  
  public MyFieldType(bool value) {
    _valueBool = value;
  }
  
  public bool GetBool() {
    return _valueBool;
  }
  
  public DateTime GetDateTime() {
    return _valueDateTime;
  }

  public static implicit operator MyFieldType(bool value) {
    return new MyFieldType(value);
  }
  
  public static implicit operator MyFieldType(DateTime value) {
    return new MyFieldType(value);
  }
  
  public static implicit operator DateTime(MyFieldType value) {
    return value.GetDateTime();
  }
  
  public static implicit operator bool(MyFieldType value) {
    return value.GetBool();
  }
}

class MyClass {
  public MyFieldType? MyField;
}