Scope Variables

Question

I am trying to understand why my variable is not available for the methods.

a) I create a var at class level (so I can have access to that from any method)
b) At the constructor, I will add to this var the logged in user Id
c) Trying to get _userId variable value inside the method but I get "could not be found"

public class MyController : ControllerBase
{
private readonly string _userId;

    public MyController ()
    {
        _userId = User.Identity.GetUserId();
    }

    [HttpGet]
    public string GetUserId()
    {
        return _userId;
    }
}

Where exact I'm making the scope mistake ?

Thx guys !

Answer 1

Hi @ANB ,

To access HttpContext or User in constructor, we should use IHttpContextAccessor, so, try to modify your code as below:

public class MyController : ControllerBase  
{  
         private readonly string _userId;  
         private readonly string _username;  
         //required using Microsoft.AspNetCore.Http;  
         //required using System.Security.Claims;  

         private readonly IHttpContextAccessor  _httpContextAccessor;     
         public MyController (IHttpContextAccessor httpContextAccessor)  
         {  
             _httpContextAccessor = httpContextAccessor;  
             _userId = httpContextAccessor.HttpContext.User?.FindFirst(ClaimTypes.NameIdentifier)?.Value;  
             _username = httpContextAccessor.HttpContext.User?Identity?.Name;  
         }  
         [HttpGet]  
         public string GetUserId()  
         {  
             return _userId;  
         }  
     }  

The result is below:

Note: If you meet the IHttpContextAccessor not register error, you can register IHttpContextAccessor in configure method:

 Services.AddHttpContextAccessor();  

Reference: Access HttpContext in ASP.NET Core

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Best regards,
Dillion

Answer 2

The issue is that the User variables value is set after the constructor is called, so it’s null in the constructor. Use the above technique to access user in the constructor.