I am currently learning ASP. NET Core by writing a web application with cookie authentication. I have two tables in Azure SQL database - Users (containing login and password data) and UserLinks (which contains links used to redirect logged users to a certain page).
The thing is, after logging in, each authenticated user is supposed to be redirected to a page that is unique to that user (link to this page is stored in UserLinks table in database). I tried to implement this by using this line of code:
return RedirectToAction(db2.UserLinks.Find(user.Id).Link);
This obviously doesn't work and gets me this error message:
SqlNullValueException: Data is Null. This method or property cannot be called on Null values
which means that the Find() method is not appropriate here.
My question is: what is the correct way to address my table to find right UserLinks.Link corresponding to Users.Id?
All relative code (including SQL tables) is below:
Table dbo.Users:
CREATE TABLE [dbo].[Users] (
[Id] INT NOT NULL,
[Email] NVARCHAR (50) NOT NULL,
[Password] NVARCHAR (50) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
Table dbo.USerLinks (has link to dbo.Users via foreign key UserID):
CREATE TABLE [dbo].[UserLinks] (
[Post_ID] INT NOT NULL,
[UserID] INT NOT NULL,
[TableName] NVARCHAR (50) NOT NULL,
[Options] INT NULL,
[Link] NVARCHAR (MAX) NOT NULL,
PRIMARY KEY CLUSTERED ([Post_ID] ASC),
UNIQUE NONCLUSTERED ([UserID] ASC),
FOREIGN KEY ([UserID]) REFERENCES [dbo].[Users] ([Id])
);
AccountController.cs:
public class AccountController : Controller
{
private UserContext db;
private UserLinkContext db2;
public AccountController(UserContext context, UserLinkContext ulcontext)
{
db = context;
db2 = ulcontext;
}
[HttpGet]
public IActionResult Login()
{
return View();
}
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Login(LoginModel model)
{
if (ModelState.IsValid)
{
User user = await db.Users.FirstOrDefaultAsync(u => u.Email == model.Email && u.Password == model.Password);
if (user != null)
{
await Authenticate(model.Email);
return RedirectToAction(db2.UserLinks.Find(user.Id).Link);
}
ModelState.AddModelError("", "Incorrect login and(or) password");
}
return View(model);
}
private async Task Authenticate(string userName)
{
var claims = new List<Claim>
{
new Claim(ClaimsIdentity.DefaultNameClaimType, userName)
};
ClaimsIdentity id = new ClaimsIdentity(claims, "ApplicationCookie", ClaimsIdentity.DefaultNameClaimType, ClaimsIdentity.DefaultRoleClaimType);
await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(id));
}
[HttpPost]
public async Task<IActionResult> Logout()
{
await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
return RedirectToAction("Index", "Home");
}
}
Startup.cs:
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
public void ConfigureServices(IServiceCollection services)
{
string connection = Configuration.GetConnectionString("DefaultConnection");
services.AddDbContext<UserContext>(options => options.UseSqlServer(connection));
services.AddDbContext<UserLinkContext>(options => options.UseSqlServer(connection));
services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
.AddCookie(options => //CookieAuthenticationOptions
{
options.LoginPath = new Microsoft.AspNetCore.Http.PathString("/Account/Login");
});
services.AddControllersWithViews();
}
public void Configure(IApplicationBuilder app)
{
app.UseDeveloperExceptionPage();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});
}
}
