Web API CORS Preflight issues

Web API CORS Preflight issues

Web Config
-----------
<system.webServer>
    <httpProtocol>
        <!--<customHeaders>
        <add name="Access-Control-Allow-Origin" value="*" />
        <add name="Access-Control-Allow-Headers" value="*" />
        <add name="Access-Control-Allow-Methods" value="GET,POST,PUT" />
        <add name="Access-Control-Allow-Credentials" value="true" />
      </customHeaders>-->
    </httpProtocol>
    <handlers>
        <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
        <remove name="OPTIONSVerbHandler" />
        <remove name="TRACEVerbHandler" />
        <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
</system.webServer>
  
Global asax
-----------
protected void Application_BeginRequest(object sender, EventArgs e) {
	if (Context.Request.HttpMethod.Equals("OPTIONS")) {
		Response.AddHeader("Access-Control-Allow-Origin", "*");
		Response.AddHeader("Access-Control-Allow-Methods", "GET, PUT, POST");
		Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Authorization, X-DRIB-ENCRYPTED-DATA");
		Response.AddHeader("Access-Control-Allow-Credentials", "true");
		Response.AddHeader("Access-Control-Allow-Max-Age", "86400");
		Response.End();
	}
}
    
Handler
-------
protected override Task < HttpResponseMessage > SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
	if (request.Method.Method.Equals("OPTIONS")) {
		var Response = new HttpResponseMessage {
			StatusCode = System.Net.HttpStatusCode.OK
		};
		Response.Headers.Add("Access-Control-Allow-Origin", "*");
		Response.Headers.Add("Access-Control-Allow-Methods", "GET, PUT, POST");
		Response.Headers.Add("Access-Control-Allow-Headers", "Content-Type, Authorization, X-DRIB-ENCRYPTED-DATA");
		Response.Headers.Add("Access-Control-Allow-Credentials", "true");
		Response.Headers.Add("Access-Control-Allow-Max-Age", "86400");
		var Tsc = new TaskCompletionSource < HttpResponseMessage > ();
		Tsc.SetResult(Response);
		return Tsc.Task;
	}
	return base.SendAsync(request, cancellationToken);
}