Angular 使用带web api2的角度8的CORS原点误差

我正在使用web api 2开发angular 8。当我试图登录调用下面的链接时，它给了我这个错误

CORS策略已阻止从源“”访问“”处的XMLHttpRequest:请求的资源上不存在“访问控制允许源”标头

这是我的密码

  public Login(apiUrl: any, itemName: any): Observable<any> {
  const body = 'userName=' + itemName.UserName + '&password=' + itemName.Password + '&grant_type=password';
  const options = { headers: new HttpHeaders({
    'Content-Type': 'application/x-www-form-urlencoded'
   }) };
  return this.http.post(this.loginUrl + apiUrl, body, options);
}

这是我用来验证用户身份的服务

public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            try
            {
                context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" });
                IdentityUser user = await _repo.FindUser(context.UserName, context.Password);
                var roles = await _repo.GetRolesAsync(user.Id);
                if (user == null)
                {
                    context.SetError("invalid_grant", "The user name or password is incorrect.");
                    return;
                }
                var identity = new ClaimsIdentity(context.Options.AuthenticationType);
                identity.AddClaim(new Claim("UserName", context.UserName));
                identity.AddClaim(new Claim("userId", user.Id));
                context.Validated(identity);

            }
            catch (Exception ex)
            {
                throw ex;
            }

        }

---

您需要从您的服务中删除响应头，因为您在启动类中允许cors，这在这里没有意义

public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            try
            {
                IdentityUser user = await _repo.FindUser(context.UserName, context.Password);
                var roles = await _repo.GetRolesAsync(user.Id);
                if (user == null)
                {
                    context.SetError("invalid_grant", "The user name or password is incorrect.");
                    return;
                }
                var identity = new ClaimsIdentity(context.Options.AuthenticationType);
                identity.AddClaim(new Claim("UserName", context.UserName));
                identity.AddClaim(new Claim("userId", user.Id));
                context.Validated(identity);

            }
            catch (Exception ex)
            {
                throw ex;
            }

        }

---

非常感谢，这很有帮助。

public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            try
            {
                IdentityUser user = await _repo.FindUser(context.UserName, context.Password);
                var roles = await _repo.GetRolesAsync(user.Id);
                if (user == null)
                {
                    context.SetError("invalid_grant", "The user name or password is incorrect.");
                    return;
                }
                var identity = new ClaimsIdentity(context.Options.AuthenticationType);
                identity.AddClaim(new Claim("UserName", context.UserName));
                identity.AddClaim(new Claim("userId", user.Id));
                context.Validated(identity);

            }
            catch (Exception ex)
            {
                throw ex;
            }

        }