If, like me, this was the top result when search for the same error regarding UWP, see the below:
The code I had which was throwing the error (no mapping for the unicode character exists..):
var storageFile = await Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.GetFileAsync(fileToken);
using (var stream = await storageFile.OpenAsync(FileAccessMode.Read))
{
using (var dataReader = new DataReader(stream))
{
await dataReader.LoadAsync((uint)stream.Size);
var json = dataReader.ReadString((uint)stream.Size);
return JsonConvert.DeserializeObject<T>(json);
}
}
What I changed it to so that it works correctly
var storageFile = await Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.GetFileAsync(fileToken);
using (var stream = await storageFile.OpenAsync(FileAccessMode.Read))
{
T data = default(T);
using (StreamReader astream = new StreamReader(stream.AsStreamForRead()))
using (JsonTextReader reader = new JsonTextReader(astream))
{
JsonSerializer serializer = new JsonSerializer();
data = (T)serializer.Deserialize(reader, typeof(T));
}
return data;
}