Bad Request (400) when using Web API Authentication Authentication from Angualr JS

I want to set up web API token authentication using Angular JS as client. I am very new to this concept of Token authentication inside Web API.

I don't want to use the default ASP.NET Identity tables to add or authenticate a user. I have my own database and table called "EmployeeAccess" which contains EmployeeNumber as User Id and Password. I want to authenticate users against the values ​​in this table, and then I want to provide a token so that they get permission to call it later. I have used all the OWIN and ASP.NET references needed to achieve the result. Here is my code for the various components: -

Global.asax

public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
           // AreaRegistration.RegisterAllAreas();
            GlobalConfiguration.Configure(WebApiConfig.Register);

        }

        protected void Application_BeginRequest()
        {
            if (HttpContext.Current.Request.HttpMethod == "OPTIONS")
            {
                // Cache the options request.
                HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", HttpContext.Current.Request.Headers["Origin"]);
                HttpContext.Current.Response.AddHeader("Access-Control-Allow-Methods", "GET, PUT, DELETE, POST, OPTIONS");
                HttpContext.Current.Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Accept, Authorization");
                HttpContext.Current.Response.AddHeader("Access-Control-Max-Age", "1728000");
                HttpContext.Current.Response.End();
            }
        }
    }

      

        
        
        
      

    

WebApiConfig.cs

public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {            
            // Web API routes
            config.MapHttpAttributeRoutes();

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

            config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
            config.Formatters.Remove(config.Formatters.XmlFormatter);

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

      

        
        
        
      

    

Startup.cs

[assembly: OwinStartup(typeof(Application.WebAPI.Startup))]

namespace Application.WebAPI
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=316888
            app.UseCors(Microsoft.Owin.Cors.CorsOptions.AllowAll);
            var myProvider = new AuthorizationServerProvider();
            OAuthAuthorizationServerOptions options = new OAuthAuthorizationServerOptions
            {
                AllowInsecureHttp = true,
                TokenEndpointPath = new PathString("/Token"),
                AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
                Provider = myProvider
            };
            app.UseOAuthAuthorizationServer(options);
        }
    }
}

      

        
        
        
      

    

AuthorizationServerProvider.cs

 public class AuthorizationServerProvider : OAuthAuthorizationServerProvider
    {
        public override async Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
        {
            context.Validated(); // 
        }

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

            EmployeeAccessBLL chkEmpAccessBLL = new EmployeeAccessBLL();
            EmployeeAccessViewModel vmEmployeeAccess = chkEmpAccessBLL.CheckEmployeeAccess(Convert.ToInt32(userId), password);

            if(vmEmployeeAccess != null)
            {
                var identity = new ClaimsIdentity(context.Options.AuthenticationType);
                identity.AddClaim(new Claim("username", vmEmployeeAccess.EmpName));
                context.Validated(identity);
            }
            else
            {
                context.SetError("invalid_grant", "Provided username and password is incorrect");
                return;
            }
        }               
    } 

      

        
        
        
      

    

login.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.0/angular.min.js"></script>
    <script src="../Scripts/AngularControllers/LoginController.js"></script>
    <script src="../Scripts/AngularServices/ApiCallService.js"></script>
</head>
<body ng-app="appHome">
    <div ng-controller="ctrlLogin">
        <label>Employee Number</label>
        <input type="text" id="txtEmpNumber" ng-model="md_empnumber" />
        <br/>
        <br/>
        <label>Password</label>
        <input type="text" id="txtEmpNumber" ng-model="md_password"  />

        <button id="btnAdd" type="submit" ng-click="Login()">Login</button>
    </div>
</body>
</html>

      

        
        
        
      

    

LoginController.js

var myApp = angular.module('appHome', []);
myApp.controller("ctrlLogin", ['$scope', 'MetadataOrgFactory', '$location', function ($scope, MetadataOrgFactory, $location) {
    $scope.Login = function () {
        var objLogin = {
            'username' : $scope.md_empnumber,
            'password' : $scope.md_password,
            'grant_type' : 'password'
        };

        MetadataOrgFactory.postLoginCall('Token', objLogin, function (dataSuccess) {
            alert("Welcome " + dataSuccess);           
        }, function (dataError) {
        });
    }
}]);

      

        
        
        
      

    

ApiCallService.js

var appService = angular.module('appHome');
appService.factory('MetadataOrgFactory', ['$http', function ($http) {

    var url = 'http://localhost:60544';    
    var dataFactory = {};    
    dataFactory.postLoginCall = function (controllerName, objData, callbackSuccess, callbackError) {

        $http.post(url + '/' + controllerName, objData,{headers:{ 'Content-Type': 'application/x-www-form-urlencoded' }}).then
            (function success(response) {
                alert("Success");
                callbackSuccess(response.data);
            }, function error(response) {
                callbackError(response.status);
            });
    };
    return dataFactory;
}])

      

        
        
        
      

    

When I click the "Login" button, I get below the error message: -

POST http: // localhost: 60544 / Token 400 (failed request)

When I debugged the WebAPI code, I found that this "GrantResourceOwnerCredentials ()" method inside "AuthorizationServerProvider.cs" never runs. An error message appears before this. Only the "ValidateClientAuthentication" and "MatchEndpoint" methods are executed.

Please help me to run the Token Authentication script successfully. If any code turns out to be redundant, please let me know so I can remove it.