Code In English

CodeInEnglish.cs

void Main()
{
	// Requirement: I want an Account that can have any type of identifier:
	//   Could a business analyst understand this code?
	var accountWithInteger = new Account<int> { 
		Id = 3, 
		Name = "has integer key"};

	var accountWithString = new Account<string> { 
		Id = "Stringy", 
		Name = "has string key" };

	Assert.IsTrue(() => accountWithInteger.Id is string)
		.Dump($"{accountWithInteger}?");

	Assert.IsTrue(() => accountWithString.Id is int)
		.Dump($"{accountWithString}?");

	var accountList = new List<object> {
		accountWithInteger,
		accountWithString
	};

	accountList.Dump();
	
	Assert.IsTrue(() => accountList
		.OfType<IsAccount<int>>().Any())
		.Dump("Are there any accounts with integer ids?");

	Assert.IsTrue(() => accountList
		.OfType<IsAccount<string>>().Any())
		.Dump("Are there any accounts with string ids?");
}

interface IsAccount<Key> {
	Key Id {get; set;}
	string Name {get; set;}
}

class Account<Key> : IsAccount<Key>
{
	public Key Id { get; set; }
	public string Name { get; set; }
	public override string ToString()
	{
		return $"Account Id = {Id.ToString()}, Name = {Name}";
	}
}

class Assert {
	public static bool IsTrue(Func<bool> assertion) {
		return assertion() == true;
	}
}

Paste into Linqpad :)

If you use FluentAssertions this could be even clearer.