var imageConverter = new ImageSourceConverter();
this.Logo.Source = (ImageSource)imageConverter.ConvertFromString("Assets/LogoQA.jpg");

using System;
using System.Globalization;
using System.Windows.Data;
using System.Windows.Media;

namespace Fox.Silverlight.Converters
{
    /// <summary>
    /// Converts <see cref="System.String"/>
    /// to <see cref="ImageSourceConverter"/>, <see cref="TypeConverter"/> object.
    /// </summary>
    public class StringToImageSourceConverter : IValueConverter
    {
        /// <summary>
        /// Modifies the source data before passing it to the target for display in the UI.
        /// </summary>
        /// <param name="value">The source data being passed to the target.</param>
        /// <param name="targetType">The <see cref="T:System.Type"/> of data expected by the target dependency property.</param>
        /// <param name="parameter">An optional parameter to be used in the converter logic.</param>
        /// <param name="culture">The culture of the conversion.</param>
        /// <returns>
        /// The value to be passed to the target dependency property.
        /// </returns>
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var location = value as string;
            if (location == null) return null;
            return (new ImageSourceConverter()).ConvertFromString(location);
        }

        /// <summary>
        /// Modifies the target data before passing it to the source object.  This method is called only in <see cref="F:System.Windows.Data.BindingMode.TwoWay"/> bindings.
        /// </summary>
        /// <param name="value">The target data being passed to the source.</param>
        /// <param name="targetType">The <see cref="T:System.Type"/> of data expected by the source object.</param>
        /// <param name="parameter">An optional parameter to be used in the converter logic.</param>
        /// <param name="culture">The culture of the conversion.</param>
        /// <returns>
        /// The value to be passed to the source object.
        /// </returns>
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}