polly.dib

#!csharp

#r "nuget: Polly, 7.2.3"
using Polly;
using System.IO; 

#!csharp

string filename = @"C:\tmp\in.txt";

var fileRetryPolicy = Polly.Policy.Handle<System.IO.FileNotFoundException>().WaitAndRetry(5, retryAttempt => {Console.WriteLine("retry " + retryAttempt); return TimeSpan.FromSeconds((Math.Pow(2, retryAttempt))); });

// Writing to file with a retry that fails and is not handled if the file is readonly because the policy does not handle System.UnauthorizedAccessException
// fileRetryPolicy.Execute(() => File.AppendAllText(filename, DateTime.UtcNow.ToString() + Environment.NewLine)); 

string contents = fileRetryPolicy.Execute<string>(() => { return File.ReadAllText(filename);});
Console.WriteLine(contents);

var fileUnauthorizedPolicy = Polly.Policy.Handle<System.UnauthorizedAccessException>().Fallback( () => Console.WriteLine("File is locked readonly"));
fileUnauthorizedPolicy.Execute(() => File.AppendAllText(filename, DateTime.UtcNow.ToString() + Environment.NewLine));