如何在 class 中使用 blazor 范围服务

Question

I am trying to use a scoped service for AuthenticationStateProvider to get user details in different classes of the solution. The service class that is used as scoped service looks like this:

public class ServiceClass
{
    private readonly AuthenticationStateProvider _authenticationStateProvider;

    public ServiceClass(AuthenticationStateProvider authenticationStateProvider)
    {
        _authenticationStateProvider = authenticationStateProvider;
    }
    public async Task<string> GetIdentity()
    {
        var authState = await _authenticationStateProvider.GetAuthenticationStateAsync();
        var user = authState.User;
        return user.Identity.Name;
    }}

I registered the class in startup as scoped service like this:

services.AddScoped<ServiceClass>();

Then trying to consume the service in another class DAL like this

 public class DAL
{

    private readonly ServiceClass userClass;
    public async Task<bool> saveBankCash(TransactionBankCashHeader master, List<TransactionBankCashDetail> lines, string Doctype)
    {


        string user = await userClass.GetIdentity();
    }
}

But in the saveBankCash method, userClass is null, can someone please guide me what is wrong here?

Answer 1

You will need to add a constructor to DAL like this:

public DAL(ServiceClass s)
{
 userClass = s; 
}

Note that this will only work if you add DAL to the DI as well, like this:

services.AddScoped<DAL>();

The DI will then inject the dependencies in the call to the constructor.