Xamarin 表单与 Firebase。 数据检索抛出 System.InvalidCastException: '指定的转换无效。'

Question

 public async Task<IEnumerable<Users>> GetAllUsers()
        {
               return (await firebase
              .Child("Users")
              .OnceAsync<Users>()).Select(item => new Users
              {
                  UserName= item.Object.UserName.ToString(),
                  Password = item.Object.Password.ToString(),
                  Role  = item.Object.Role.ToString()
              }).ToList();
        }

I am a beginner to App development. While retriving the data from the Firebase Realtime database getting the above error. Scratching head for 4 hours. Please help.

Answer 1

You don't have to cast it toString(). Firebase casts types on its own, when you push that object on Firebase Realtime database, it will automatically assign correct type when you pull it back.Get rid of the ToString() on each property and see if that fixes the issue.

public async Task<IEnumerable<Users>> GetAllUsers()
    {
           return (await firebase
          .Child("Users")
          .OnceAsync<Users>()).Select(item => new Users
          {
              UserName= item.Object.UserName,
              Password = item.Object.Password,
              Role  = item.Object.Role
          }).ToList();
    }