错误ArgumentNullException未处理

Question

我指的是这个http://www.dotnetcurry.com/ShowArticle.aspx?ID=585从sql server检索到窗口电话的图像，并有错误ArgumentNullException时，它运行在那个高亮行。

public class ImageConverter : IValueConverter 
    { 
     public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
     { 
      byte[] buffer = value as byte[]; 
      **Stream memStream = new MemoryStream(buffer);** 
      WriteableBitmap wbimg = PictureDecoder.DecodeJpeg(memStream); 
      return wbimg; 
     } 
     public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
     { 
      return null; 
     } 
    } 

我发现了另一个类似的帖子和我有同样的错误。 http://forums.create.msdn.com/forums/p/74224/452127.aspx 但不明白编码..任何人都知道如何解决错误？

Answer 1

看起来像值为空或不是字节数组。

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
{ 
    WriteableBitmap wbimg = null; 

    if (value != null && value is byte[]) { 
     byte[] buffer = value as byte[]; 
     Stream memStream = new MemoryStream(buffer); 
     wbimg = PictureDecoder.DecodeJpeg(memStream); 
    } 

    return wbimg; 
}