public class Customer
{
    public int Id { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public string Role{ get; set; }
}

public class MyAuthorizationServerProvider : OAuthAuthorizationServerProvider
{

    public override async Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
    {
        context.Validated(); //
    }

    public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
    {
        var identity = new ClaimsIdentity(context.Options.AuthenticationType);


        if (context.UserName == "user" && context.Password == "pass")
        {
            identity.AddClaim(new Claim(ClaimTypes.Role, "user"));
            identity.AddClaim(new Claim("username", "user"));
            identity.AddClaim(new Claim(ClaimTypes.Name, "Suresh Sha"));
            context.Validated(identity);
        }
        else
        {
            context.SetError("invalid_grant", "Provided username and password is incorrect");
            return;
        }
    }
}

if (context.UserName == "user" && context.Password == "pass")
    {
        identity.AddClaim(new Claim(ClaimTypes.Role, "user"));
        identity.AddClaim(new Claim("username", "user"));
        identity.AddClaim(new Claim(ClaimTypes.Name, "NAME"));
        context.Validated(identity);
    }

public partial class Startup
{
    public void Configuration(IAppBuilder app)
    {
        //enable cors origin requests
        app.UseCors(Microsoft.Owin.Cors.CorsOptions.AllowAll);

        var myProvider = new MyAuthorizationServerProvider();
        OAuthAuthorizationServerOptions options = new OAuthAuthorizationServerOptions
        {
            AllowInsecureHttp = true,
            TokenEndpointPath = new PathString("/token"),
            AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
            Provider = myProvider
        };
        app.UseOAuthAuthorizationServer(options);
        app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

        //my code


        HttpConfiguration config = new HttpConfiguration();
        WebApiConfig.Register(config);

        //ConfigureAuth(app);
    }
}