csharp-property-wrapper.cs

using System;

[System.Runtime.CompilerServices.PropertyWrapper]
public class Expirable<TValue> : Attribute
{
    private TimeSpan duration;
    private DateTime expirationDate;
    
    private TValue? innerValue = null;

    public TValue? Value
    {
        get => return HasExpired ? null : innerValue;
        set
        {
            expirationDate = DateTime.Now + duration;
            innerValue = value;
        }
    }

    public Expirable(TimeSpan duration)
    {
        this.duration = duration;
    }

    private bool HasExpired => expirationDate < DateTime.Now;
}

public struct Tokens
{
    [Expirable(duration: TimeSpan.FromSeconds(3))]
    static string AuthenticationToken { get; set; }
}

Tokens.AuthenticationToken = "asdijoaisjdoiajsd";

System.Threading.Thread.Sleep(TimeSpan.FromSeconds(2));
Console.WriteLine(Tokens.AuthenticationToken); // prints the token
System.Threading.Thread.Sleep(TimeSpan.FromSeconds(2));
Console.WriteLine(Tokens.AuthenticationToken); // prints null