ASP.NET Core 在 Razorpages 上声明空处理

Question

I was wondering what is the most clean approach to handle null checking for claims? Right now my pages look polluted with all the null checking and i'm already using custom extensions and claims

var value = User.GetUserId(); // get ClaimType.UserId
if(string.IsNullOrWhiteSpace(value))
{
    throw new NullReferenceException();
}

int userId;
if(!int.TryParse(value, out userId))
{
    throw new NullReferenceException();
}

now if i get more claims than

var value = User.GetUserId(); // get ClaimsType.UserId
var value2 = User.GetEmail(); // get ClaimsType.Email
if(string.IsNullOrWhiteSpace(value) || string.IsNullOrWhiteSpace(value2))
{
    throw new NullReferenceException();
}

int userId;
if(!int.TryParse(value, out userId))
{
    throw new NullReferenceException();
}

and i have to use it constantly on my Get and Post handlers.

Is there a way to keep this shorter or ommit it?

Answer 1

You can create a Custom Attribute that has these checks then decorate the ActionResult with it. Or, you could create Filters .

If you want to learn more about Custom Attributes , check this doc: https://docs.microsoft.com/en-us/dotnet/standard/attributes/writing-custom-attributes

If you want to learn more about Filters , check this doc: https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-2.2

The whole idea is to have something like this:

public class CheckClaimsAttribute : Attribute
{
    //your checks here
}

Then

[HttpGet]
[CheckClaims]
public IActionResult MyGetMethod() {...}

[HttpPost]
[CheckClaims]
public IActionResult MyPostMethod() {...}