title: Signing POST form in C# for uploading to Amazon S3
body: <p>I am having trouble signing my policy documents for the Amazon S3.</p>
  
  <p>There are examples on how to do it in Ruby, Java, and Python, but when I try to do it in C#, it's not working out. I keep getting an invalid signature, and I'm not sure where I'm going wrong.
  <a href="http://aws.amazon.com/articles/1434" rel="nofollow">http://aws.amazon.com/articles/1434</a></p>
  
  <p>Can anyone provide an example like those in the article, except for C#?</p>
  
  <p>Thanks.</p>