I have this model:

 public class Model
 {
     public IdentityUser UserId { get; set; }
     public string data{ get; set; }

     public decimal data2{ get; set; }
     public DateTime data3{ get; set; }
 }

And this function:

 using (SqlConnection connection = new SqlConnection(connectionString))
 {
     connection.Open();

     string sql = "SELECT UserId, data, data2, data3 FROM Table;
     using (SqlCommand command = new SqlCommand(sql, connection))
     {
         using (SqlDataReader reader = await command.ExecuteReaderAsync())
         {
             while (reader.Read())
             {
                 Model test = new Model
                     {
                         UserId = reader.GetString(0) // error, can not convert from Identity to string
                         data = reader.GetString(1),
                         data2 = reader.GetDecimal(2),
                         data3 = reader.GetDateTime(3)
                     };

                 list.Add(test);
             }
         }
     }

Before this, I populated the data from the table and was able to display the data for a specific user using command.Parameters.AddWithValue("@UserId", userId); and I obtained the userId in the function:

    protected override async Task OnInitializedAsync()
    {
        var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
        var user = authState.User;
        if (user != null)
        {
            userId = user.Identity.Name;
        }
    }

I want to display in a blazor page a table with all data from that table but I cannot get the UserId because I don’t know how to read it using SqlDataReader