Response to preflight request doesn't pass access control check (Angular2)

I got it resolved by adding following lines to web.config.

<system.webServer>   <modules runAllManagedModulesForAllRequests="true">   </modules></system.webServer>

Thanks.

Adding Access-Control-Allow-Origin header for the preflight request during Application_BeginRequest in Global.asax.cs worked for me.

Global.asax/Global.asax.cs

protected void Application_BeginRequest(Object sender, EventArgs e)    {        // Preflight request comes with HttpMethod OPTIONS        if (HttpContext.Current.Request.HttpMethod == "OPTIONS")                    {            HttpContext.Current.Response.AddHeader("Cache-Control", "no-cache");            HttpContext.Current.Response.AddHeader("Access-Control-Allow-Methods", "GET, POST");                           // The following line solves the error message            HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", "*");            // If any http headers are shown in preflight error in browser console add them below            HttpContext.Current.Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Accept, Pragma, Cache-Control, Authorization ");            HttpContext.Current.Response.AddHeader("Access-Control-Max-Age", "1728000");            HttpContext.Current.Response.End();        }    }

After solving this issue, the application threw errors on browser console that certain headers are not mentioned in preflight response.

Once the headers were added to Access-Control-Allow-Headers header of the preflight response it got resolved.

protected void Application_BeginRequest(Object sender, EventArgs e){    // Preflight request comes with HttpMethod OPTIONS        // The following line solves the error message        HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", "*");    if (HttpContext.Current.Request.HttpMethod == "OPTIONS")                {        HttpContext.Current.Response.AddHeader("Cache-Control", "no-cache");        HttpContext.Current.Response.AddHeader("Access-Control-Allow-Methods", "GET, POST");                       // If any http headers are shown in preflight error in browser console add them below        HttpContext.Current.Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Accept, Pragma, Cache-Control, Authorization ");        HttpContext.Current.Response.AddHeader("Access-Control-Max-Age", "1728000");        HttpContext.Current.Response.End();    }}

This above code worked fine