C# Settings Custom Type List add not working

Question

I created some custom settings types:

[SettingsSerializeAs(SettingsSerializeAs.Xml)]
public class PathSetting
{
    public PathSetting(string path = "", bool enabled = true)
    {
        Path = path;
        Enabled = enabled;
    }

    public string Path {get; set;}
    public bool Enabled { get; set; }
}

And

[SettingsSerializeAs(SettingsSerializeAs.Xml)]
public class PathUserSettings : ApplicationSettingsBase
{
    private List<PathSetting> paths;
    public List<PathSetting> Paths
    {
        get { return paths; }
        set { paths = value; }
    }
}

Then in my Settings.setting file I created an item called paths of type (Browse > myNamespace.PathUserSettings. I didn't set it to anything and then in my main for on form load I put this code:

if (Properties.Settings.Default.paths == null)
        {
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("prefs/*.pref"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("levels/*.mis"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("User Data/"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("core/prefs.cs"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("scripts/client/prefs.cs"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("scripts/server/prefs.cs"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("scripts/client/config.cs"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("xml/Swarms.xml"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("xml/OldSwarms.xml"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("art/props/*"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("art/swarm/*"));
            Properties.Settings.Default.paths.Paths.Add(new PathSetting("art/datablocks/convertedDatablocks.cs"));
            Properties.Settings.Default.Save();
        }

But for some reason it doesn't get past the first Add call. I cant even really step in. Can you not add to a list? I don't fully understand how the settings systems works and there doesn't seem to be that many examples like this.

Any help is appreciated!

Answer 1

Well, the first thing I noticed is a logical flaw here:

if (Properties.Settings.Default.paths == null)
{
   Properties.Settings.Default.paths.Paths.Add(new PathSetting("prefs/*.pref"));

That would case an exception as Properties.Settings.Default.paths is null.

You certainly can add elements to a list, but it has to be initialized first (!= null).

Eg.

var list = new List<string()>;

I can't help you in a more specific way as I have not clear what is the type of Properties.Settings.Default object.

Answer 2

Put it in a try-catch block and see what the exception is. Probably a NullException since you look like you have a typo. Did you mean != null ?

Answer 3

LittleSweatSeas pointed out one issue, but I'm doubtful the code you provided is what you were executing, since .paths is a private field. You couldn't be using Properties.Settings.Default.paths from outside the class and be able to compile the code. Perhaps you were running "last successful build" as Visual Studio will let you do when your code can't build: Visual Studio: Re-enable "Build failed, run last success?" dialogue box

The code you listed is never going to work, it is either going to throw NullReferenceException, or not execute at all:

if (Properties.Settings.Default.paths == null)
    {
        Properties.Settings.Default.paths.Paths.Add(new PathSetting("prefs/*.pref"));

It doesn't matter if the property is readonly or not, the logic you listed will only ever cause a NullReferenceExeception, because of your if expression.

Since you are the author of the property, you are going about initializing the wrong way. You don't initialize private fields from outside the class. Initialize the .path field in the constructor for your custom property class (UserPathSettings).

public UserPathSettings() {
    this.paths = new List<PathSettings>();  // instantiate the object (this. for clarity)
}

or give the property a default (a lazy property). Custom "settings" are often initialized in the getter, per Microsoft's examples. Here is one: http://msdn.microsoft.com/en-us/library/system.configuration.defaultsettingvalueattribute%28v=vs.100%29.aspx

public List<PathSetting> Paths
{
    get { return paths != null ? paths : new List<PathSettings>(); }
    set { paths = value; }
}

Now you will never have a null property. Judging by your question, you may be a little confused about properties vs fields, or maybe you just worked an all-nighter and your eyes were bugging, so you may want to do a little googling on that or get some sleep. :D

If you want to access the property from outside the class, you need to use the public property (uppercase .Path, not .path):

Properties.Settings.Default.Paths.Add(...)