Image source changing in C# for windows phone 8.1 RT

Question

I want to change image source in runtime using C#. I tried this.

In the MainPage.xaml,

<Image x:Name="myImage" HorizontalAlignment="Left"
               Height="125"
               Margin="86,76,0,0"
               VerticalAlignment="Top"
               Width="220" />
        <Button Content="Button"
                HorizontalAlignment="Left"
                Margin="134,230,0,0"
                VerticalAlignment="Top"
                Click="Button_Click"/>

and in the MainPage.xaml.cs

private void Button_Click(object sender, RoutedEventArgs e)
        {
            myImage.Source = new BitmapImage(new Uri("/Assets/WorldCupFlags/Sri_Lanka.png", UriKind.Relative));
        }

It shows no compile time error but when I run this and click the Button it shows an exception. It says "An exception of type 'System.ArgumentException' occurred in mscorlib.ni.dll but was not handled in user code."

Answer 1

Within an async code block, do this:

imgMyImageControl.Source = await GetBitmapAsFile("Folder\ImageFileName.png");

The GetBimpageAsFile function:

    /// <summary>
    /// Gets a bitmap image stored on the local file system
    /// </summary>
    /// <param name="strIFile">The input file path name</param>
    /// <returns>The requested bitmap image, if successful; else, null</returns>
    public static async Task<BitmapImage> GetBitmapAsFile(string strIFile)
    {
        try
        {
            StorageFile fOut = null;
            BitmapImage biOut = null;
            FileRandomAccessStream fasGet = null;

            if (!strIFile.Equals(""))
            {
                fOut = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync(strIFile);
                if (fOut != null)
                {
                    fasGet = (FileRandomAccessStream)await fOut.OpenAsync(FileAccessMode.Read);
                    if (fasGet != null)
                    {
                        biOut = new BitmapImage();

                        if (biOut != null)
                        {
                            await biOut.SetSourceAsync(fasGet);

                            return biOut;
                        }
                        else
                            YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "Bitmap [" + strIFile + "] is not set.");
                    }
                    else
                        YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "File stream [" + strIFile + "] is not set.");
                }
            }
            else
                YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "Input file path name is empty.");
        }
        catch (Exception ex)
        {
            YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "[" + strIFile + "] " + ex.Message);
        }

        return null;
    }

Answer 2

The hint is in the exception:

The given System.Uri cannot be converted into a Windows.Foundation.Uri

You need to use an absolute URI for Universal XAML apps:

myImage.Source = new BitmapImage(new Uri(
  "ms-appx:///Assets/WorldCupFlags/Sri_Lanka.png", UriKind.Absolute));