How can I save application settings in a Windows Forms application?

If you work with Visual Studio then it is pretty easy to get persistable settings. Right click on the project in Solution Explorer and choose Properties. Select the Settings tab and click on the hyperlink if settings doesn't exist.

Use the Settings tab to create application settings. Visual Studio creates the files Settings.settings and Settings.Designer.settings that contain the singleton class Settings inherited from ApplicationSettingsBase. You can access this class from your code to read/write application settings:

Properties.Settings.Default["SomeProperty"] = "Some Value";
Properties.Settings.Default.Save(); // Saves settings in application configuration file

This technique is applicable both for console, Windows Forms, and other project types.

Note that you need to set the scope property of your settings. If you select Application scope then Settings.Default. will be read-only.

Reference: How To: Write User Settings at Run Time with C# - Microsoft Docs

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If you are planning on saving to a file within the same directory as your executable, here's a nice solution that uses the JSON format:

using System;
using System.IO;
using System.Web.Script.Serialization;

namespace MiscConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            MySettings settings = MySettings.Load();
            Console.WriteLine("Current value of 'myInteger': " + settings.myInteger);
            Console.WriteLine("Incrementing 'myInteger'...");
            settings.myInteger++;
            Console.WriteLine("Saving settings...");
            settings.Save();
            Console.WriteLine("Done.");
            Console.ReadKey();
        }

        class MySettings : AppSettings<MySettings>
        {
            public string myString = "Hello World";
            public int myInteger = 1;
        }
    }

    public class AppSettings<T> where T : new()
    {
        private const string DEFAULT_FILENAME = "settings.json";

        public void Save(string fileName = DEFAULT_FILENAME)
        {
            File.WriteAllText(fileName, (new JavaScriptSerializer()).Serialize(this));
        }

        public static void Save(T pSettings, string fileName = DEFAULT_FILENAME)
        {
            File.WriteAllText(fileName, (new JavaScriptSerializer()).Serialize(pSettings));
        }

        public static T Load(string fileName = DEFAULT_FILENAME)
        {
            T t = new T();
            if(File.Exists(fileName))
                t = (new JavaScriptSerializer()).Deserialize<T>(File.ReadAllText(fileName));
            return t;
        }
    }
}

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The registry is a no-go. You're not sure whether the user which uses your application, has sufficient rights to write to the registry.

You can use the app.config file to save application-level settings (that are the same for each user who uses your application).

I would store user-specific settings in an XML file, which would be saved in Isolated Storage or in the SpecialFolder.ApplicationData directory.

Next to that, as from .NET 2.0, it is possible to store values back to the app.config file.

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The ApplicationSettings class doesn't support saving settings to the app.config file. That's very much by design; applications that run with a properly secured user account (think Vista UAC) do not have write access to the program's installation folder.

You can fight the system with the ConfigurationManager class. But the trivial workaround is to go into the Settings designer and change the setting's scope to User. If that causes hardships (say, the setting is relevant to every user), you should put your Options feature in a separate program so you can ask for the privilege elevation prompt. Or forego using a setting.

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The registry/configurationSettings/XML argument still seems very active. I've used them all, as the technology has progressed, but my favourite is based on Threed's system combined with Isolated Storage.

The following sample allows storage of an objects named properties to a file in isolated storage. Such as:

AppSettings.Save(myobject, "Prop1,Prop2", "myFile.jsn");

Properties may be recovered using:

AppSettings.Load(myobject, "myFile.jsn");

It is just a sample, not suggestive of best practices.

internal static class AppSettings
{
    internal static void Save(object src, string targ, string fileName)
    {
        Dictionary<string, object> items = new Dictionary<string, object>();
        Type type = src.GetType();

        string[] paramList = targ.Split(new char[] { ',' });
        foreach (string paramName in paramList)
            items.Add(paramName, type.GetProperty(paramName.Trim()).GetValue(src, null));

        try
        {
            // GetUserStoreForApplication doesn't work - can't identify.
            // application unless published by ClickOnce or Silverlight
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForAssembly();
            using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(fileName, FileMode.Create, storage))
            using (StreamWriter writer = new StreamWriter(stream))
            {
                writer.Write((new JavaScriptSerializer()).Serialize(items));
            }

        }
        catch (Exception) { }   // If fails - just don't use preferences
    }

    internal static void Load(object tar, string fileName)
    {
        Dictionary<string, object> items = new Dictionary<string, object>();
        Type type = tar.GetType();

        try
        {
            // GetUserStoreForApplication doesn't work - can't identify
            // application unless published by ClickOnce or Silverlight
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForAssembly();
            using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(fileName, FileMode.Open, storage))
            using (StreamReader reader = new StreamReader(stream))
            {
                items = (new JavaScriptSerializer()).Deserialize<Dictionary<string, object>>(reader.ReadToEnd());
            }
        }
        catch (Exception) { return; }   // If fails - just don't use preferences.

        foreach (KeyValuePair<string, object> obj in items)
        {
            try
            {
                tar.GetType().GetProperty(obj.Key).SetValue(tar, obj.Value, null);
            }
            catch (Exception) { }
        }
    }
}

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I wanted to share a library I've built for this. It's a tiny library, but a big improvement (IMHO) over .settings files.

The library is called Jot (GitHub). Here is an old The Code Project article I wrote about it.

Here's how you'd use it to keep track of a window's size and location:

public MainWindow()
{
    InitializeComponent();

    _stateTracker.Configure(this)
        .IdentifyAs("MyMainWindow")
        .AddProperties(nameof(Height), nameof(Width), nameof(Left), nameof(Top), nameof(WindowState))
        .RegisterPersistTrigger(nameof(Closed))
        .Apply();
}

The benefit compared to .settings files: There's considerably less code, and it's a lot less error-prone since you only need to mention each property once.

With a settings files you need to mention each property five times: once when you explicitly create the property and an additional four times in the code that copies the values back and forth.

Storage, serialization, etc. are completely configurable. When the target objects are created by an IoC container, you can [hook it up][] so that it applies tracking automatically to all objects it resolves, so that all you need to do to make a property persistent is slap a [Trackable] attribute on it.

It's highly configurable, and you can configure: - when data is persisted and applied globally or for each tracked object - how it's serialized - where it's stored (e.g. file, database, online, isolated storage, registry) - rules that can cancel applying/persisting data for a property

Trust me, the library is top notch!

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A simple way is to use a configuration data object, save it as an XML file with the name of the application in the local Folder and on startup read it back.

Here is an example to store the position and size of a form.

The configuration dataobject is strongly typed and easy to use:

[Serializable()]
public class CConfigDO
{
    private System.Drawing.Point m_oStartPos;
    private System.Drawing.Size m_oStartSize;

    public System.Drawing.Point StartPos
    {
        get { return m_oStartPos; }
        set { m_oStartPos = value; }
    }

    public System.Drawing.Size StartSize
    {
        get { return m_oStartSize; }
        set { m_oStartSize = value; }
    }
}

A manager class for saving and loading:

public class CConfigMng
{
    private string m_sConfigFileName = System.IO.Path.GetFileNameWithoutExtension(System.Windows.Forms.Application.ExecutablePath) + ".xml";
    private CConfigDO m_oConfig = new CConfigDO();

    public CConfigDO Config
    {
        get { return m_oConfig; }
        set { m_oConfig = value; }
    }

    // Load configuration file
    public void LoadConfig()
    {
        if (System.IO.File.Exists(m_sConfigFileName))
        {
            System.IO.StreamReader srReader = System.IO.File.OpenText(m_sConfigFileName);
            Type tType = m_oConfig.GetType();
            System.Xml.Serialization.XmlSerializer xsSerializer = new System.Xml.Serialization.XmlSerializer(tType);
            object oData = xsSerializer.Deserialize(srReader);
            m_oConfig = (CConfigDO)oData;
            srReader.Close();
        }
    }

    // Save configuration file
    public void SaveConfig()
    {
        System.IO.StreamWriter swWriter = System.IO.File.CreateText(m_sConfigFileName);
        Type tType = m_oConfig.GetType();
        if (tType.IsSerializable)
        {
            System.Xml.Serialization.XmlSerializer xsSerializer = new System.Xml.Serialization.XmlSerializer(tType);
            xsSerializer.Serialize(swWriter, m_oConfig);
            swWriter.Close();
        }
    }
}

Now you can create an instance and use in your form's load and close events:

    private CConfigMng oConfigMng = new CConfigMng();

    private void Form1_Load(object sender, EventArgs e)
    {
        // Load configuration
        oConfigMng.LoadConfig();
        if (oConfigMng.Config.StartPos.X != 0 || oConfigMng.Config.StartPos.Y != 0)
        {
            Location = oConfigMng.Config.StartPos;
            Size = oConfigMng.Config.StartSize;
        }
    }

    private void Form1_FormClosed(object sender, FormClosedEventArgs e)
    {
        // Save configuration
        oConfigMng.Config.StartPos = Location;
        oConfigMng.Config.StartSize = Size;
        oConfigMng.SaveConfig();
    }

And the produced XML file is also readable:

<?xml version="1.0" encoding="utf-8"?>
<CConfigDO xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <StartPos>
    <X>70</X>
    <Y>278</Y>
  </StartPos>
  <StartSize>
    <Width>253</Width>
    <Height>229</Height>
  </StartSize>
</CConfigDO>

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Yes, it is possible to save the configuration - but it pretty much depends on the way you choose to do it. Let me describe the technical differences so you can understand the options you have:

First, you need to distinguish, whether you want to use applicationSettings or AppSettings in your *.exe.config(aka App.config in Visual Studio) file - there are fundamental differences, being described here.

Both provide different ways of saving changes:

The AppSettings allow you to read and write directly into the config file via config.Save(ConfigurationSaveMode.Modified);, where config is defined as: config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

The applicationSettings allow to read, but if you write changes (via Properties.Settings.Default.Save();) it will be written on a per-user basis, stored in a special place (e.g. C:\Documents and Settings\USERID\Local Settings\Application Data\FIRMNAME\WindowsFormsTestApplicati_Url_tdq2oylz33rzq00sxhvxucu5edw2oghw\1.0.0.0). As Hans Passant mentioned in his answer, this is because a user usually has restricted rights to Program Files and cannot write to it without invoking the UAC prompt. A disadvantage is if you're adding configuration keys in the future you need to synchronize them with every user profile.

But there are a couple of other alternative options:

Since .NET Core (and .NET 5 and 6) a 3rd option is the appsettings.json file which uses Microsoft's configuration abstraction (and also the secrets.json file which is stored in your user profile rather than in the assemblies directories). But usually WinForms isn't using it, so I am mentioning it just for completeness. However, here are some references how to read and write the values. Alternatively you can use Newtonsoft JSON to read and write the appsettings.json file, but it is not limited to that: you can also create your own json files with that method.

As mentioned in the question, there is a 4th option: If you treat the configuration file as XML document, you can load, modify and save it by using the System.Xml.Linq.XDocument class. It is not required to use a custom XML file, you can read the existing config file; for querying elements, you can even use Linq queries. I have given an example here, check out the function GetApplicationSetting there in the answer.

A 5th option is to store settings in the registry. How you can do it is described here.

Last not least, there is a 6th option: You can store values in the environment (system environment or environment of your account). In Windows settings (the cogwheel in the Windows menu), type in "environment" in the search bar and add or edit them there. To read them, use var myValue = Environment.GetEnvironmentVariable("MyVariable");. Note that your application usually needs to be restarted to get the updated environment settings.

If you require encryption to protect your values, check out this answer. It describes how to use Microsoft's DPAPI to store values encrypted.

And if you want to support your own files, whether XML or JSON, it might be useful to know the directory of the assembly running:

var assemblyDLL = System.Reflection.Assembly.GetExecutingAssembly();
var assemblyDirectory = System.IO.Path.GetDirectoryName(assemblyDLL.Location);

You can use assemblyDirectory as base directory to store your files.

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I don't like the proposed solution of using web.config or app.config. Try reading your own XML. Have a look at XML Settings Files – No more web.config.

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"Does this mean that I should use a custom XML file to save configuration settings?" No, not necessarily. We use SharpConfig for such operations.

For instance, if a configuration file is like that

[General]
# a comment
SomeString = Hello World!
SomeInteger = 10 # an inline comment

We can retrieve values like this

var config = Configuration.LoadFromFile("sample.cfg");
var section = config["General"];

string someString = section["SomeString"].StringValue;
int someInteger = section["SomeInteger"].IntValue;

It is compatible with .NET 2.0 and higher. We can create configuration files on the fly and we can save it later.

Source: http://sharpconfig.net/
GitHub: https://github.com/cemdervis/SharpConfig

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Other options, instead of using a custom XML file, we can use a more user friendly file format: JSON or YAML file.

If you use .NET 4.0 dynamic, this library is really easy to use (serialize, deserialize, nested objects support and ordering output as you wish + merging multiple settings to one) JsonConfig (usage is equivalent to ApplicationSettingsBase)

For .NET YAML configuration library... I haven't found one that is as easy to use as JsonConfig

You can store your settings file in multiple special folders (for all users and per user) as listed here Environment.SpecialFolder Enumeration and multiple files (default read only, per role, per user, etc.)

Sample for getting path of special folder: C# getting the path of %AppData%

If you choose to use multiple settings, you can merge those settings: For example, merging settings for default + BasicUser + AdminUser. You can use your own rules: the last one overrides the value, etc.

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As far as I can tell, .NET does support persisting settings using the built-in application settings facility:

The Application Settings feature of Windows Forms makes it easy to create, store, and maintain custom application and user preferences on the client computer. With Windows Forms application settings, you can store not only application data such as database connection strings, but also user-specific data, such as user application preferences. Using Visual Studio or custom managed code, you can create new settings, read them from and write them to disk, bind them to properties on your forms, and validate settings data prior to loading and saving. - http://msdn.microsoft.com/en-us/library/k4s6c3a0.aspx

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Sometimes you want to get rid of those settings kept in the traditional web.config or app.config file. You want more fine grained control over the deployment of your settings entries and separated data design. Or the requirement is to enable adding new entries at runtime.

I can imagine two good options:

The strongly typed version and

The object oriented version.

The advantage of the strongly typed version are the strongly typed settings names and values. There is no risk of intermixing names or data types. The disadvantage is that more settings have to be coded, cannot be added at runtime.

With the object oriented version the advantage is that new settings can be added at runtime. But you do not have strongly typed names and values. Must be careful with string identifiers. Must know data type saved earlier when getting a value.

You can find the code of both fully functional implementations HERE.

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public static class SettingsExtensions
{
    public static bool TryGetValue<T>(this Settings settings, string key, out T value)
    {
        if (settings.Properties[key] != null)
        {
            value = (T) settings[key];
            return true;
        }

        value = default(T);
        return false;
    }

    public static bool ContainsKey(this Settings settings, string key)
    {
        return settings.Properties[key] != null;
    }

    public static void SetValue<T>(this Settings settings, string key, T value)
    {
        if (settings.Properties[key] == null)
        {
            var p = new SettingsProperty(key)
            {
                PropertyType = typeof(T),
                Provider = settings.Providers["LocalFileSettingsProvider"],
                SerializeAs = SettingsSerializeAs.Xml
            };
            p.Attributes.Add(typeof(UserScopedSettingAttribute), new UserScopedSettingAttribute());
            var v = new SettingsPropertyValue(p);
            settings.Properties.Add(p);
            settings.Reload();
        }
        settings[key] = value;
        settings.Save();
    }
}

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