ReadExcelFileWithPolly.cs

using System;
using System.IO;
using Polly;

namespace SpreadsheetImporter
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadFile(@"C:\temp\jam2.xls");
            Console.ReadLine();
        }

        private static void ReadFile(string filePath)
        {
            var policy = Policy
                .Handle<IOException>()
                 .WaitAndRetry(new[]
                  {
                    TimeSpan.FromSeconds(10),
                    TimeSpan.FromSeconds(20),
                    TimeSpan.FromSeconds(30)
                  }, (exception, timeSpan) => {
                      Console.WriteLine("Please Close the file and try again");
                  }); 
            try
            {
                policy.Execute(() => Console.WriteLine(ReadAllText(filePath)));
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Something has gone wrong, see exception message: {ex.Message}");
            }
        }

        private static string ReadAllText(string filePath)
        {
            return $"Content of file is: {File.ReadAllText(filePath)}";
        }
    }
}