using System;

using System.Threading;

using System.Threading.Tasks;

public class AsyncLazyCustom<T>

{

    private readonly Func<Task<T>> _factory;

    private Task<T> _task;

​

    private bool _initialized;

​

    private object _lock;

​

    public AsyncLazyCustom(Func<Task<T>> factory)

    {

        _factory = factory;

    }

​

    public async Task<T> Value()

    {

        try

        {

            return await LazyInitializer.EnsureInitialized(ref _task, ref _initialized, ref _lock, _factory);

        }

        catch

        {

            Volatile.Write(ref _initialized, false);

            throw;

        }

    }

}

​

public class CachingKeyVaultCertificateAuthorityProvider

{

    private readonly AsyncLazyCustom<string> _certificateAuthorityLazy;

    public bool ThrowException { get; set; } = true;

    public CachingKeyVaultCertificateAuthorityProvider()

    {

        _certificateAuthorityLazy = new AsyncLazyCustom<string>(

            async () => await GetCertificateAuthorityInternalAsync().ConfigureAwait(false));

    }

    public Task<string> GetCertificateAuthorityAsync()

    {

        return _certificateAuthorityLazy.Value();

    }

    internal async Task<string> GetCertificateAuthorityInternalAsync()

    {

        if (ThrowException)

        {

            throw new Exception("exception was thrown");

        }

        return await Task.FromResult("this is the certificate");

    }

}

​

public class Program

{

    public static void Main()

    {

        CachingKeyVaultCertificateAuthorityProvider provider = new CachingKeyVaultCertificateAuthorityProvider();

        Console.WriteLine("throw exception: " + provider.ThrowException);

        TryLogCertificateAuthority(provider);

        provider.ThrowException = false;

        Console.WriteLine("throw exception: " + provider.ThrowException);

        TryLogCertificateAuthority(provider);

    }

    public static void TryLogCertificateAuthority(CachingKeyVaultCertificateAuthorityProvider provider)

    {

        try

        {

            string cert = provider.GetCertificateAuthorityAsync().GetAwaiter().GetResult();

            Console.WriteLine(cert);

        }

        catch (Exception ex)

        {

            Console.WriteLine(ex.Message);

        }

    }

}

​