Bind byte array to image in windows phone 8.1 xaml

I bind byte array to image source in my windows phone application.

XAML:

 <Border Background="{ThemeResource ListViewItemPlaceholderBackgroundThemeBrush}" Margin="0,9.5,0,0" Grid.Column="0" HorizontalAlignment="Left">
                    <Image Source="{Binding EventPicture}" Stretch="UniformToFill" AutomationProperties.Name="{Binding Title}" Height="79" Width="79"/>
                </Border>

It's a part of item template of ListView in HubSection. Items are bind from view model and it got them from service in json format.

Data retrieving code:

public async Task<ObservableCollection<SocialEvent>> GetSocialEventsAsync()
{
    var socialEvents = new ObservableCollection<SocialEvent>();
    var httpClient = new HttpClient();
    var jsonResponse = await httpClient.GetStringAsync(string.Format("{0}{1}",BaseUrl,"socialevents/1"));
    var eventArray = JsonConvert.DeserializeObject<SocialEvent[]>(jsonResponse);
    foreach (var evnt in eventArray)
    {
        socialEvents.Add(evnt);
    }
    return socialEvents;
}

The problem is that I get this in my application

I'm 100% sure that images is in the right format, at least I checked the base64 string in json response. Also I tried to re-size image and many other things with layout. I wrote a converter from byte[] to ImageSource but there was no result too.

Any ideas guys?

P.S. Sorry for my English, I hope you understand me ;)