Struct.cs

public struct Id
{
    private long _id;

    public Id(long id)
    {
        this._id = id;
    }

    public static implicit operator Id(long value)
    {
        return new Id(value);
    }

    public static implicit operator long(Id id)
    {
        return id._id;
    }
}

void Main()
{
    Id myId = 10L;
    long value = myId;

    value.Dump();
}