如何从 Xamarin 中的 Firebase 获取价值？

Question

如何使用 Xamarin Firebase.Database Android 从 Firebase 实时数据库获取数据，因为没有可用的文档并且我是新用户。

public void GetSubjects()
{
   Database.Reference.Child("childName").Ref.AddListenerForSingleValueEvent(new ValueEventListener());
}

public class ValueEventListener : Java.Lang.Object, Firebase.Database.IValueEventListener
{

    public void OnCancelled( DatabaseError error )
    {
       throw new NotImplementedException();
    }

    public void OnDataChange( DataSnapshot snapshot )
    {

      //How to Get Value from Snapshot?
      ClassName a = snapshot.GetValue(ClassName) //Gives Error

    }

Answer 1

看看这个，看看它是否有效......

private void GetData()
{
    FirebaseDatabase
        .Instance
        .Reference
        .Child("Put your child node name here")
        .AddListenerForSingleValueEvent(new DataValueEventListener());
}


class DataValueEventListener: Java.Lang.Object, IValueEventListener
{
    public void OnCancelled(DatabaseError error)
    {
        // Handle error however you have to
    }

    public void OnDataChange(DataSnapshot snapshot)
    {
        if (snapshot.Exists())
        {
            DataModelClass model = new DataModelClass();
            var obj = snapshot.Children;

            foreach (DataSnapshot snapshotChild in obj.ToEnumerable())
            {
                if (snapshotChild.GetValue(true) == null) continue;

                model.PropertyName = snapshotChild.Child("Put your firebase attribute name here")?.GetValue(true)?.ToString();
                model.PropertyName = snapshotChild.Child("Put your firebase attribute name here")?.GetValue(true)?.ToString();

                // Use type conversions as required. I have used string properties only
            }
        }
    }
}

Answer 2

也许你可以试试这个

internal class DAOFood
{
    FirebaseClient firebase = new FirebaseClient("YOUR FIREBASE URL");
    public DAOFood()
    {
    }

    public async Task<List<Food>> GetAllFoods()
    {
        List<Food> lstFood = (await firebase.
            Child("Food").
            OnceAsync<Food>()).Select(item => new Food
            {
                FoodId = item.Object.FoodId,
                FoodName = item.Object.FoodName
            }).ToList();
        return lstFood;
    }
}