Error :Request header field Content-Type is not allowed by Access-Control-Allow-Headers

I created an mvc4 web api project using vS2012. I used following tutorial to solve the Cross-Origin Resource Sharing, "http://blogs.msdn.com/b/carlosfigueira/archive/2012/07/02/cors-support-in-asp-net-web-api-rc-version.aspx". It is working successfully, and i post data from client side to server successfully.

After that for implementing Autherization in my project, I used the following tutorial to implement OAuth2, "http://community.codesmithtools.com/CodeSmith_Community/b/tdupont/archive/2011/03/18/oauth-2-0-for-mvc-two-legged-implementation.aspx". This is help me for getting RequestToken on client side.

But when i post data from client side, i got the error, "XMLHttpRequest cannot load http://. Request header field Content-Type is not allowed by Access-Control-Allow-Headers."

My client side code look like,

 function PostLogin() {
    var Emp = {};            
    Emp.UserName = $("#txtUserName").val();             
    var pass = $("#txtPassword").val();
    var hash = $.sha1(RequestToken + pass);
            $('#txtPassword').val(hash);
    Emp.Password= hash;
    Emp.RequestToken=RequestToken;
    var createurl = "http://localhost:54/api/Login";
    $.ajax({
        type: "POST",
        url: createurl,
        contentType: "application/json; charset=utf-8",
        data: JSON.stringify(Emp),
        statusCode: {
                200: function () {
                $("#txtmsg").val("done");                       
                toastr.success('Success.', '');                         
                }
                },
        error:
            function (res) {                        
                toastr.error('Error.', 'sorry either your username of password was incorrect.');            
                }
        });
    };

My api controller look like,

    [AllowAnonymous]
    [HttpPost]
    public LoginModelOAuth PostLogin([FromBody]LoginModelOAuth model)
    {
        var accessResponse = OAuthServiceBase.Instance.AccessToken(model.RequestToken, "User", model.Username, model.Password, model.RememberMe);

        if (!accessResponse.Success)
        {
            OAuthServiceBase.Instance.UnauthorizeToken(model.RequestToken);
            var requestResponse = OAuthServiceBase.Instance.RequestToken();

            model.ErrorMessage = "Invalid Credentials";

            return model;
        }
        else
        {
            // to do return accessResponse

            return model;
        }

    } 

My webconfig file look like,

 <configuration>
   <configSections>   
   <section name="entityFramework"    type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  <section name="oauth" type="MillionNodes.Configuration.OAuthSection, MillionNodes, Version=1.0.0.0, Culture=neutral"/>
  <sectionGroup name="dotNetOpenAuth" type="DotNetOpenAuth.Configuration.DotNetOpenAuthSection, DotNetOpenAuth.Core">
  <section name="messaging" type="DotNetOpenAuth.Configuration.MessagingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
  <section name="reporting" type="DotNetOpenAuth.Configuration.ReportingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
</sectionGroup>
</configSections>
<oauth defaultProvider="DemoProvider" defaultService="DemoService">
<providers>
  <add name="DemoProvider" type="MillionNodes.OAuth.DemoProvider, MillionNodes" />
</providers>
<services>
  <add name="DemoService" type="MillionNodes.OAuth.DemoService, MillionNodes" />
</services>
</oauth>
<system.web>
 <httpModules>
   <add name="OAuthAuthentication" type="MillionNodes.Module.OAuthAuthenticationModule, MillionNodes, Version=1.0.0.0, Culture=neutral"/>
  </httpModules>
 <compilation debug="true" targetFramework="4.0" />
<authentication mode="Forms">
  <forms loginUrl="~/Account/Login" timeout="2880" />
</authentication>
<pages>
  <namespaces>
    <add namespace="System.Web.Helpers" />
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Optimization" />
    <add namespace="System.Web.Routing" />
    <add namespace="System.Web.WebPages" />
  </namespaces>
</pages>
</system.web>
<system.webServer>
 <validation validateIntegratedModeConfiguration="false" />      
  <modules>
      <add name="OAuthAuthentication"     type="MillionNodes.Module.OAuthAuthenticationModule, MillionNodes, Version=1.0.0.0, Culture=neutral" preCondition="" />
 </modules>
 <httpProtocol>
  <customHeaders>
    <add name="Access-Control-Allow-Origin" value="*" />
    </customHeaders>
  </httpProtocol>
</system.webServer>
<dotNetOpenAuth>
<messaging>
  <untrustedWebRequest>
    <whitelistHosts>
      <!-- Uncomment to enable communication with localhost (should generally not activate in production!) -->
      <!--<add name="localhost" />-->
    </whitelistHosts>
  </untrustedWebRequest>
</messaging>
<!-- Allow DotNetOpenAuth to publish usage statistics to library authors to improve the library. -->
<reporting enabled="true" />

Solution 1:

As hinted at by this post Error in chrome: Content-Type is not allowed by Access-Control-Allow-Headers just add the additional header to your web.config like so...

<httpProtocol>
  <customHeaders>
    <add name="Access-Control-Allow-Origin" value="*" />
    <add name="Access-Control-Allow-Headers" value="Origin, X-Requested-With, Content-Type, Accept" />
  </customHeaders>
</httpProtocol>

Solution 2:

It is most likely due to a cross-origin request, but it may not be. For me, I had been debugging an API and had set the Access-Control-Allow-Origin to *, but it appears that recent versions of Chrome are requiring an extra header. Try prepending the following to your file if you are using PHP:

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept");

Make sure that you haven't already used header in another file, or you will get a nasty error. See the docs for more.