Extracting a byte[] from XML File

[flashkid10]

I currently have a system in a which I store an image to a byte[] (cover) in a class instance. I'm trying to extract a byte[] from the class instance, but I don't know how to do that.

the code I'm using is

List<Item> information;

information = (from e in XDocument.Load("AniListData.xml").Root.Elements("Item")
               select new Item
                      {
                          Name = (string)e.Element("Name"),
                          Age = (int)e.Element("Age"),
                          Cover = // What do i put here to extract the byte[]
                      }).ToList();

 

[JohnH]

Which string representation do you use to store the byte array? Often byte arrays are stored as Base64 strings in xml, and Convert class has convenient methods for doing so.

 

[flashkid10]

I Don't know what you mean by string representation, but I store the array in a public byte[] in the class Item and I save it to the XML by a method which contains

public static void SaveData(List<Item> obj, string filename)
{
XmlSerializer sr = new XmlSerializer(obj.GetType());
TextWriter writer = new StreamWriter(filename);
sr.Serialize(writer, obj);
writer.Close();
}

 

[jmcilhinney]

Have you tried just doing exactly what you're doing for the other properties? If you simply use:

Cover = (byte[])e.Element("Cover")

what happens? I can only really think of two possibilities:

1. It will work as is.
2. It will throw an exception.

In the case of #2, the error message will give you a clue as to what you have to do. If it says that you can't cast a string as a byte array then you know that you need to perform the conversion yourself. As JohnH says, the data is likely encoded using base-64, so you can try decoding it that way as a first effort:

Cover = Convert.FromBase64String((string)e.Element("Cover"))

 

[flashkid10]

It throws a exception in both cases

Exception thrown: 'System.ArgumentNullException' in mscorlib.dll
Additional information: Value cannot be null.

 

[jmcilhinney]

That suggests that "Cover" is not valid in that context. Unlike me, you don't have to make assumptions based on limited information. Use whatever name is appropriate in that instance.

 

[flashkid10]

I don't understand, What name should I use, because the Byte array is named "Cover"

 

[jmcilhinney]

What does the XML say you should use? Have you looked at it?

 

[JohnH]

I Don't know what you mean by string representation,

Everything in a xml file is text, and data that is not text have to be converted to text before written to xml.

but I store the array in a public byte[] in the class Item and I save it to the XML by a method which contains

public static void SaveData(List<Item> obj, string filename)
{
XmlSerializer sr = new XmlSerializer(obj.GetType());
TextWriter writer = new StreamWriter(filename);
sr.Serialize(writer, obj);
writer.Close();
}

XmlSerializer will convert byte array data to a Base64 string. Example:

<example>aGVsbG8gc2VyaWFsaXphdGlvbg==</example>

If there is no array (null) the element is not written to xml, and if there is an empty array it will write an element that has no data.

<example />

 

[flashkid10]

Okay, I got it to work, I had the default value on the array set to empty. Thank you!