Winforms - Dynamic Load / Save Settings

Question

I have a "settings file" in my Winforms application called Settings.settings with a partial class for custom methods, etc. Is there a way to load / save dynamic settings based on arbitrary keys?

For example, I have some ListViews in my application in which I want to save / load the column widths; Instead of creating a width setting for each column for each list view I would like a simple method to load / save the widths automatically.

Below is an example of the save method I have tried:

internal sealed partial class Settings
{
    public void SetListViewColumnWidths(ListView listView)
    {
        String baseKey = listView.Name;
        foreach (ColumnHeader h in listView.Columns)
        {
            String key = String.Format("{0}-{1}", baseKey, h.Index);
            this[key] = h.Width;
        }
    }
}

When running that code I get the error "The settings property 'TestsListView-0' was not found." Is there something I am missing?

Answer 1

Store your column width settings in an Xml Serializable object. Ie, something that implements IXmlSerializable then create a single setting entry of that type in Settings.settings.

A good option would probably be an Xml Serializable Dictionary. A quick google search found quite a few different blog posts that describe how to implement that.

As mentioned in other answers you'll need to ensure that this object is a User setting. You may also need to initialize the setting instance. Ie, create a XmlSerializableDictionary() instance and assign it to the setting if the setting is null. The settings subsystem doesn't create default instances of complex setting objects.

Also, if you want these settings to persist between assembly versions (ie, be upgradable) you will need to upgrade the settings on application startup. This is described in detail on Miha Markič's blog and Raghavendra Prabhu's blog.

Answer 2

I think the error

The settings property 'key' was not found.

occurs because the 'key' value does not exist in your settings file (fairly self-explanatory).

As far as I am aware, you can't add settings values programmatically, you might need to investigate adding all of the settings you need to the file after all, although once they are there, I think you'll be able to use the sort of code you've given to save changes.

To Save changes, you'll need to make sure they are 'User' settings, not 'Application'.

The Settings file is quite simple XML, so you might be able to attack the problem by writing the XML directly to the file, but I've never done it, so can't be sure it would work, or necessarily recommend that approach.

http://msdn.microsoft.com/en-us/library/cftf714c.aspx is the MSDN link to start with.

Answer 3

You can do Settings.Save() or similar on user settings, but note that such settings would NOT get persisted to the xxx.exe.config file in your app directory as you'd expect. They actually go somewhere deep inside the user folder (search your drive for xxx.exe.config to find it). Next time that you manually change xxx.exe.config in your app directory, the change will mysteriously not apply (the system is still using the saved one from the user directory).