How to retry in C#

Retry

TimeSpan nextDelay = TimeSpan.FromSeconds(2);
int retryNumber = 5;
// 監控結果
string testString = "";

for (int i = 0; i != retryNumber; i++)
{
	if (string.IsNullOrWhiteSpace(testString))
	{
		Console.WriteLine($"String is null, retry {i + 1} ...");
	}
	else
	{
		nextDelay = TimeSpan.FromSeconds(0);
	}
	// 這是非同步，所以不會有執行緒 lock 問題(重點)
	await Task.Delay(nextDelay).ConfigureAwait(false);
	// 由於是 retry, 希望每次是上一次的 2 倍時間
	nextDelay = nextDelay + nextDelay;
	
	// Test
	if (i == 2)
	{
		testString = "Not null :-)";
	}
}