ReactJS-所请求的资源上没有“ Access-Control-Allow-Origin”标头

如何解决ReactJS-所请求的资源上没有“ Access-Control-Allow-Origin”标头

我正在尝试通过asp.net Web API 2对用户进行身份验证并生成令牌。当我使用邮递员发送请求时，它将生成令牌。但是当我使用Reactjs和Axios发送请求时，它给了我一个错误。

CORS策略已阻止从原点“ http：// localhost：3000”访问http：// localhost：4093 / token处的XMLHttpRequest：请求中不存在“ Access-Control-Allow-Origin”标头资源。

错误：网络错误 在createError（createError.js：16） 在XMLHttpRequest.handleError（xhr.js：83）

获取http：// localhost：4093 / token net :: ERR_Failed

我在WebApiConfig.cs中启用了cors，并将标头添加到ApplicationOAuthProvider.cs

WebApiConfig.cs

public static class WebApiConfig
{
        public static void Register(HttpConfiguration config)
        {
            config.SuppressDefaultHostAuthentication();
            config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));

            config.MapHttpAttributeRoutes();

            EnableCorsAttribute cors = new EnableCorsAttribute("*","*","*");
            config.EnableCors(cors);

            config.Routes.MapHttpRoute(
                name: "DefaultApi",routeTemplate: "api/{controller}/{id}",defaults: new { id = RouteParameter.Optional }
            );
        }
}

ApplicationOAuthProvider.cs

public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
{
            context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin",new[] { "*" });

            var userManager = context.OwinContext.GetUserManager<ApplicationUserManager>();

            ApplicationUser user = await userManager.FindAsync(context.UserName,context.Password);

            if (user == null)
            {
                context.SetError("invalid_grant","The user name or password is incorrect.");
                return;
            }

            ClaimsIdentity oAuthIdentity = await user.GenerateUserIdentityAsync(userManager,OAuthDefaults.AuthenticationType);
            ClaimsIdentity cookiesIdentity = await user.GenerateUserIdentityAsync(userManager,CookieAuthenticationDefaults.AuthenticationType);

            AuthenticationProperties properties = CreateProperties(user.UserName);
            AuthenticationTicket ticket = new AuthenticationTicket(oAuthIdentity,properties);
            context.Validated(ticket);
            context.Request.Context.Authentication.SignIn(cookiesIdentity);
}

login.js

submitCredential = user => {
        const qs = require('querystring')

        const config = {
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8'
            }
          }

        const data = { username: user.Email,password: user.Password,grant_type: 'password' };
        axios.get('http://localhost:4093/token',qs.stringify(data),config)
            .then(response => {
                console.log(response.data);
            })
            .catch(error => {
                console.log(error);
            });
    }