如何在Windows Phone 8.1上从数据库获取和显示图像作为字节数组

Question

I want to get image as byte array from database using local WCF service and display it on a Page using Image control. I cannot make it working.

This is the simplest code just to start… Eventually I want to use binding in XAML.

//I use following code for getting bytes (it’ s working)
private async Task GetPhotoAsync(string code)
    {
        using (var httpClient = new HttpClient())
        {
            using (var request = new HttpRequestMessage(HttpMethod.Get,
                $"http://192.168.0.5/Service/TerminalService.svc/GetPhoto?Code={code}"))
            {
                using (var response = await httpClient.SendAsync(request))
                {
                    if (response.IsSuccessStatusCode)
                    {
                        ImageBuffer = (await response.Content.ReadAsByteArrayAsync());
                    }
                    else
                    {
                        throw new Exception($"Error.{Environment.NewLine}{response}");
                    }
                }
            }
        }
    }

...

public byte[] ImageBuffer
    {
        get { return _imageBuffer; }
        set { SetProperty(ref imageBuffer, value); }
    }

public class BindableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] String propertyName = null)
    {
        if (object.Equals(storage, value)) return false;
        storage = value;
        this.OnPropertyChanged(propertyName);
        return true;
    }
    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        var eventHandler = this.PropertyChanged;
        if (eventHandler != null) eventHandler(this, new PropertyChangedEventArgs(propertyName));
    }
}

...

//Method used to convert bytes into BitmapImage and set source of control Image.

public async void SetImageFromByteArray(byte[] data, Image image)
    {
        using (InMemoryRandomAccessStream raStream = new InMemoryRandomAccessStream())
        {
            using (DataWriter writer = new DataWriter(raStream))
            {
                // Write the bytes to the stream
                writer.WriteBytes(data);

                // Store the bytes to the MemoryStream
                await writer.StoreAsync();

                // Not necessary, but do it anyway
                await writer.FlushAsync();

                // Detach from the Memory stream so we don't close it
                writer.DetachStream();
            }

            raStream.Seek(0);

            BitmapImage bitMapImage = new BitmapImage();
            bitMapImage.SetSource(raStream);

            image.Source = bitMapImage;
        }
    }

When MainPage is loaded I run method GetPhotoAsync(). After a while I set Image.Source by pressing button and run method SetImageFromByteArray(). Nothing is displayed.

I also tried these solutions without success:

• with binding properties - https://marcominerva.wordpress.com/2013/04/15/how-to-convert-a-byte-array-to-image-in-a-windows-store-app/
• using converter - Windows Phone 8 - Load byte[] array into XAML image with Binding
• TaskCompletionNotifier - Async Implementation of IValueConverter

Answer 1

You can try this, it works for me.

First you have to set up property in your ViewModel which you bind the Image control to.

public BitmapImage ImageSource 
    { 
        get { return _imageSource; } 
        set { SetProperty(ref _imageSource, value); } 
    }

...

public async Task GetPhotoAsync(string twrKod)
    {
        using (var httpClient = new HttpClient())
        {
            using (var request = new HttpRequestMessage(HttpMethod.Get,
                $"http://192.168.0.5/Service/TerminalService.svc/GetPhoto?Code={code}"))
            {
                using (var response = await httpClient.SendAsync(request))
                {
                    if (response.IsSuccessStatusCode)
                    {
                        var imageStream = await response.Content.ReadAsStreamAsync();

                        var memStream = new MemoryStream();
                        await imageStream.CopyToAsync(memStream);
                        memStream.Position = 0;
                        var bitmap = new BitmapImage();
                        bitmap.SetSource(memStream.AsRandomAccessStream())
                        ImageSource = bitmap;
                    }

                }
            }
        }
    }

Make sure you have MemoryStream to be return type of WCF Service. For example:

public Stream GetPhoto(string code)
   {
        byte[] bytes = null;
        var myCommand = new SqlCommand())
        myCommand.Connection = new SqlConnection(Settings.Default.ConnectionString);
        objSql.ObjCommand.CommandText = "dbo.GetPhotoProc";
        objSql.ObjCommand.CommandType = CommandType.StoredProcedure;
        objSql.ObjCommand.Parameters.Add("@code", SqlDbType.NVarChar).Value = code;

        objSql.Reader = objSql.ObjCommand.ExecuteReader();

        if (!objSql.Reader.HasRows) return null;
        while (objSql.Reader.Read())
        {
            bytes = (byte[])objSql.Reader.GetValue(0);
        }
        if (bytes == null) return Stream.Null;
        var ms = new MemoryStream(bytes) { Position = 0 };

        if (WebOperationContext.Current != null)
            WebOperationContext.Current.OutgoingResponse.ContentType = "image/jpeg";
        return ms;
    }

Interface for WCF

[WebGet(UriTemplate = "GetPhoto?Code={code}", RequestFormat = WebMessageFormat.Xml, ResponseFormat = WebMessageFormat.Xml, BodyStyle = WebMessageBodyStyle.Bare)]
    [OperationContract]
    Stream GetPhoto(string code);