如何在不锁定文件的情况下将xml反序列化为对象？

Question

I have an xml file which i use for database, meaning that the xml is updated frequently. For the xml database have a FileWatcher, and once the xml is updated i get an event and then i deserialize the xml into object and check if there were indeed changes.

The problem that i have is that once i deserialize the xml, the Stream Reader is locking the file so i might get exceptions when trying to update it.

Is there a possibility to deserialize the xml without locking the file?

        XmlSerializer serializer = new XmlSerializer(typeof (MyType));
        Stream reader = new FileStream(File, FileMode.Open);
        var myType = (MyType) serializer.Deserialize(reader);

Answer 1

new FileStream(File, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);

FileShare.ReadWrite is the key. Please remember to put filestreams into a using-statement!

Edit: According the the comments (thanks!) there is still a problem if the other process writing to the file demands FileShare.None. This might well be the case in case of a writer. If this is the case the only solution is to operate on distinct files. I'd propose that you rename the file from "file.dat" to "file_readonly1.dat" on the first access after the write. Your reading processes can then read the file as many times as they want without blocking off the writer. The writer will just create a new file the next time it runs. Once some reader sees the new "file.dat" it will rename it to "file_readonly2.dat". From then on readers should use the newer version of the file. And so on. I think this scheme is 100% safe.

Answer 2

string xmlString = string.Empty
using (StreamReader reader = new StreamReader("xmlfile.xml"))
{
    xmlString = reader.ReadToEnd();
    // after leaving the using scope the streamreader is disposed freeing the file
}

// if the serializer needs a TextReader then you can wrap it here
StringReader strReader = new strReader(xmlString);

var xmlObject = (MyType) serializer.Deserialize(strReader)