How can I watch the user.config file and reload the settings when it changes?

Question

I have a situation where I am running multiple instances of my WPF application. I want the instances to share the same user.config file. Currently, whichever instance writes t

Answer 1

You should Cache the file and implement CacheDependency so that if any change is made to the file the file gets reloaded in the Cache. I am using a permission xml file in my application which gets stored in the cache and reloaded if file gets changed. Here's the code:

protected void Page_Load(object sender, EventArgs e)
{
        XmlDocument permissionsDoc = null;

        if (Cache["Permissions"] == null)
        {
            string path = Server.MapPath("~/XML/Permissions.xml");
            permissionsDoc = new XmlDocument();
            permissionsDoc.Load(Server.MapPath("~/XML/Permissions.xml"));
            Cache.Add("Permissions", permissionsDoc,
                            new CacheDependency(Server.MapPath("~/XML/Permissions.xml")),
                           Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration,
                    CacheItemPriority.Default, new CacheItemRemovedCallback(ReloadPermissionsCallBack));
        }
        else
        {
            permissionsDoc = (XmlDocument)Cache["Permissions"];
        }
}

private void ReloadPermissionsCallBack(string key, object value, CacheItemRemovedReason reason)
    {
        XmlDocument doc = new XmlDocument();
        doc.Load(Server.MapPath("~/XML/Permissions.xml"));
        Cache.Insert("Permissions", doc ,
                            new CacheDependency(Server.MapPath("~/XML/Permissions.xml")),
                           Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration,
                    CacheItemPriority.Default, new CacheItemRemovedCallback(ReloadPermissionsCallBack));
    }

Caching will also increase your application performance.

Answer 2

I found it. The following code will return the path to the user.config file. You need to add a reference to System.Configuration.dll

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
string path = config.FilePath;

Now I can use a FileSystemWatcher to get notified when the file changes.

Answer 3

could you use the fileSystemWatcher control?

it has a modified event you can trigger