public static async Task <DataSourceContent <T> > GetItemsAsync <T>(string key) where T : BindableSchemaBase
{
string json = null;
if (_memoryCache.ContainsKey(key))
{
json = _memoryCache[key];
}
else
{
json = await UserStorage.ReadTextFromFile(key);
_memoryCache[key] = json;
}
if (!String.IsNullOrEmpty(json))
{
try
{
DataSourceContent <T> records = JsonConvert.DeserializeObject <DataSourceContent <T> >(json);
return(records);
}
catch (Exception ex)
{
AppLogs.WriteError("AppCache.GetItems", ex);
}
}
return(null);
}
internal async Task <DataSourceContent <T> > UpdateCache()
{
var freshData = new DataSourceContent <T>()
{
TimeStamp = DateTime.Now,
Items = await LoadDataAsync()
};
await AppCache.AddItemsAsync(CacheKey, freshData);
return(freshData);
}
public static async Task AddItemsAsync <T>(string key, DataSourceContent <T> data) where T : BindableSchemaBase
{
try
{
string json = JsonConvert.SerializeObject(data);
await UserStorage.WriteText(key, json);
if (_memoryCache.ContainsKey(key))
{
_memoryCache[key] = json;
}
else
{
_memoryCache.Add(key, json);
}
}
catch (Exception ex)
{
AppLogs.WriteError("AppCache.AddItems", ex);
}
}
public async Task <DateTime> LoadDataAsync(ObservableCollection <T> viewItems, bool forceRefresh)
{
DateTime timeStamp = DateTime.Now;
if (HasStaticData)
{
viewItems.AddRangeUnique(await LoadDataAsync());
}
else
{
var dataInCache = await AppCache.GetItemsAsync <T>(CacheKey);
if (dataInCache != null)
{
timeStamp = dataInCache.TimeStamp;
viewItems.AddRangeUnique(dataInCache.Items);
}
if (NetworkInterface.GetIsNetworkAvailable() && DataNeedToBeUpdated(forceRefresh, dataInCache))
{
var freshData = new DataSourceContent <T>()
{
TimeStamp = DateTime.Now,
Items = await LoadDataAsync()
};
timeStamp = freshData.TimeStamp;
viewItems.AddRangeUnique(freshData.Items);
await AppCache.AddItemsAsync(CacheKey, freshData);
}
}
return(timeStamp);
}
private bool DataNeedToBeUpdated(bool forceRefresh, DataSourceContent <T> dataInCache)
{
return(dataInCache == null || forceRefresh || IsContentExpirated(dataInCache.TimeStamp));
}
