Question

I have this open-source library that I’m having some trouble fixing a problem… This library allows to easily create an XML file to store application settings. But I’m having an issue saving the changes.

I have another application where I’m using this library and every time that application window is done resizing, I call the Save() method of the library to save the window size/position to the XML file.

Most of times it works fine, everything is saved. Once in a while though, I get an exception saying the file is being used by another process.

I really need to make sure that changes are saved every time the Save() method is called, I need to handle this exception somehow or prevent it from happening.

What are you guys suggestions for best handling this situation?

The code for the Save() method is the following:

public void Save() {
    // Create a new XML file if there's no root element
    if(xDocument.DocumentElement == null) {
        xDocument = new XmlDocument();
        xDocument.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\" ?>\n" +
            "<" + XmlRootElement + ">\n</" + XmlRootElement + ">");
    }

    // OMITTED CODE WAS HERE (NOT IMPORTANT FOR THE PROBLEM)

    // Create a new XML writer for the XML file
    XmlWriter xWriter = XmlWriter.Create(XmlFilePath, new XmlWriterSettings() {
        Indent = true,
        IndentChars = "\t"
    });

    // Sort the XML file using the XSL sylesheet and save it
    xslTransform.Transform(xDocument, xWriter);

    // Clear the buffer and close the XML writer stream
    xWriter.Flush();
    xWriter.Close();
}

Answer 1

It could be the case that the window-resizing-completed events are firing so quickly, that the save function is being called, the called again before it finishes running the first time. This would result in the error you’re describing (the other process using the file is… YOU!). Try surrounding your code with a lock, thusly:

lock(some_shared_object)
{
    //Your code here
}