Blazor ProtectedSessionStorage 对象 NULL

Question

I've made a helper class on ProtectedSessionStorage to Read/Write data

using Microsoft.AspNetCore.ProtectedBrowserStorage;
public class SessionObjectHelper
{
    [Inject] private ProtectedSessionStorage ProtectedSessionStore { get; set; }
    
    public async Task<string> GetTestProperty()
    {
        var value = await ProtectedSessionStore.GetAsync<string>("TestProperty") ?? string.Empty;

        return value;
    }
    
    public async Task SetTestProperty(string value)
    {
        await ProtectedSessionStore.SetAsync("TestProperty", value);
    }       
}

If I call any of these methods from a Component as illustrated below, ProtectedSessionStore is always NULL

[Inject] private SessionObjectHelper SessionObjectHelper { get; set; }

protected override async Task OnInitializedAsync()
{
    var testProperty= await SessionObjectHelper.GetTestProperty();
}

Answer 1

Your SessionObjectHelper class should declare a constructor to get the injected service, not use the [Inject] attribute, eg

    public class SessionObjectHelper
    {
        private ProtectedSessionStorage storage;

        public SessionObjectHelper(ProtectedSessionStorage storage)
        {
                this.storage = storage;
        }

The [Inject] attribute is designed to work with Razor Components, not regular classes.

You can then use

[Inject] public SessionObjectHelper SessionObjectHelper { get; set; }

In your component. Note I changed to public - if it's private the runtime won't be able to see/set it.