title: How to create RSACryptoServiceProvide using string private key
body: <p>I <strong>only</strong> have a private key. i want to use it for signing data in RSA algorithm.
  i know how to use certificate to sign data. but i don't any way to use private key in string format to create and use <code>RSACryptoServiceProvider</code></p>
  
  <p>My code looks something like this.</p>
  
  <pre><code>string privateKey = "-----BEGIN PRIVATE KEY-----\nsometext\nsometext\nsometext\.....\n-----END PRIVATE KEY-----\n"
  var rasAlg = new RSACryptoServiceProvider()// how can i use my private key here.
  var signature = rasAlg.SignData(bytesArray, new SHA256CryptoServiceProvider());
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>if any one can help me create X509Certificate then also it is fine.</p>