EqualsMistake #5.cs

class CustomerId
{
	public CustomerId(string value)
	{
		this.Value = value;
	}

	public readonly string Value;

	public override bool Equals(object obj)
	{
		if (ReferenceEquals(null, obj)) return false;
		if (obj.GetType() != GetType()) return false;
		return string.Equals(this.Value, ((CustomerId)obj).Value, StringComparison.OrdinalIgnoreCase);
	}

	public override int GetHashCode()
	{
		return this.Value.GetHashCode();
	}
}

new CustomerId("ABC") == new CustomerId("abc") // True; that's a good thing

new HashSet<CustomerId>
{
	new CustomerId("ABC")
}.Contains(new CustomerId("abc"));		// False! Bad!