title: HttpClient throws System.ArgumentException: 'windows-1251' is not a supported encoding name
body: <p>I am writing WinPhone 8.1 app. 
  Code is very simple and works in most cases:</p>
  
  <pre><code>string htmlContent;
  using (var client = new HttpClient())
  {
      htmlContent = await client.GetStringAsync(GenerateUri());
  }
  _htmlDocument.LoadHtml(htmlContent);
  </code></pre>
  
  <p>But sometimes exception is thrown at </p>
  
  <pre><code>htmlContent = await client.GetStringAsync(GenerateUri());
  </code></pre>
  
  <blockquote>
    <p>InnerException    {System.ArgumentException: 'windows-1251' is not a
    supported encoding name. Parameter name: name    at
    System.Globalization.EncodingTable.internalGetCodePageFromName(String
    name)    at
    System.Globalization.EncodingTable.GetCodePageFromName(String name)<br>
    at
    System.Net.Http.HttpContent.&lt;>c__DisplayClass1.b__0(Task
    task)}    System.Exception {System.ArgumentException}</p>
  </blockquote>
  
  <p>Does HttpClient support 1251 encoding? And if it doesn't, how can I avoid this problem? Or is it target page problem? Or am I wrong in something?</p>