title: System.Runtime.Serialization.Json nuget package error on .NetStandard
body: <p>I've posted an issue on <a href="https://github.com/dotnet/standard" rel="nofollow noreferrer">.NetStandard repository</a> but they just didn't care for 12 days for now.. So, I wanted to try Stackoverflow. Here is <a href="https://github.com/dotnet/standard/issues/571" rel="nofollow noreferrer">the link of my issue</a>.</p>
  
  <p>I've started to use .NetCore version=1.0.0-preview2-003121 with Visual Studio 2015. My project.json file is below:</p>
  
  <pre><code>{
    "version": "1.0.0-*",
    "frameworks": {
      "netstandard2.0": {
        "dependencies": {
          "System.Runtime.Serialization.Xml": "4.3.0",
          "System.Runtime.Serialization.Json": "4.3.0"
        }
      }
    }
  }
  </code></pre>
  
  <p>My code file is below:</p>
  
  <pre><code>using System.Runtime.Serialization;
  using System.Runtime.Serialization.Json;
  
  namespace NetCoreTests
  {
      public class Class1
      {
          public Class1()
          {
              XmlObjectSerializer ser = new DataContractJsonSerializer(typeof(int));
          }
      }
  }
  </code></pre>
  
  <p>And this is the error I get when I try to build the solution:</p>
  
  <pre><code>CS0029  Cannot implicitly convert type 'System.Runtime.Serialization.Json.DataContractJsonSerializer' 
  to 'System.Runtime.Serialization.XmlObjectSerializer'   NetCoreTests..NETStandard,Version=v2.0
  </code></pre>
  
  <p>Looks like <code>DataContractJsonSerializer</code> class in System.Runtime.Serialization.Json nuget package doesn't inherit <code>XmlObjectSerializer</code> class in System.Runtime.Serialization.Xml nuget package. I can see that in general there's no dependency between these 2 nuget packages; however, if you check 4 and later versions of .Net Framework <code>DataContractJsonSerializer</code> always inherits from <code>XmlObjectSerializer</code> because as far as I know every DataContractSerializer inherits from <code>XmlObjectSerializer</code>. Even in this repository this inheritance exists:
  <a href="https://github.com/dotnet/standard/blob/master/netstandard/ref/System.Runtime.Serialization.cs#L332" rel="nofollow noreferrer">https://github.com/dotnet/standard/blob/master/netstandard/ref/System.Runtime.Serialization.cs#L332</a></p>
  
  <p>What can you advice for me about this situation? Am I doin something wrong?</p>