Custom path of the user.config

Question

It hasn't been easy to find good info on implementing a custom settings provider so I'm including a complete implementation below (bottom.) The format of the user.config file is retained, as well as the functionality within the .settings designer. I'm certain there are parts that can be cleaned up a bit, so don't hassle me :)

Like others, I wanted to change the location of the user.config file and still get the fun and fanciness of working with the .settings files in the designer, including creating default values for new installations. Importantly, our app also already has other saved settings objects at a path (appData\local\etc) in which we have already decided, and we didn't want artifacts in multiple locations.

The code is much longer than I'd like it to be, but there is no SHORT answer that I could find. Though it seems somewhat painful just to be able to control the path, creating a custom settings provider in itself is still pretty powerful. One could alter the follwing implementation to store the data just about anywhere including a custom encrypted file, database, or interact with a web serivice.

From what I've read, Microsoft does not intend on making the path to the config file configurable. I'll take their word for it when they say allowing that would be scary. See (this) post. Alas, if you want to do it yourself you must implement your own SettingsProvider.

Here goes..

Add a reference in your project to System.Configuration, you'll need it to implement the SettingsProvider.

Easy bit...Create a class which implements SettingsProvider, use ctrl+. to help you out.

class CustomSettingsProvider : SettingsProvider

Another easy bit...Go to the code behind of your .settings file (there is a button in the designer) and decorate the class to point it to your implementation. This must be done to override the built in functionality, but it does not change how the designer works.(sorry the formatting here is weird)

[System.Configuration.SettingsProvider(typeof(YourCompany.YourProduct.CustomSettingsProvider))]

public sealed partial class Settings
{
    //bla bla bla
}

Getting the path: There is a property called "SettingsKey" (e.g. Properties.Settings.Default.SettingsKey) I used this to store the path. I made the following property.

/// <summary>
/// The key this is returning must set before the settings are used.
/// e.g. <c>Properties.Settings.Default.SettingsKey = @"C:\temp\user.config";</c>
/// </summary>
private string UserConfigPath
{
    get
    {
        return Properties.Settings.Default.SettingsKey;
    }

}

Storing the settings values. I chose to use a dictionary. This will get used extensively in a bit. I created a struct as a helper.

/// <summary>
/// In memory storage of the settings values
/// </summary>
private Dictionary<string, SettingStruct> SettingsDictionary { get; set; }

/// <summary>
/// Helper struct.
/// </summary>
internal struct SettingStruct
{
    internal string name;
    internal string serializeAs;
    internal string value;
}

The magic. You must override 2 methods, GetPropertyValues and SetPropertyValues. GetPropertyValues recieves as a parameter what you see in the designer, you have to opportunity to update the values and return a new collection. SetPropertyValues is called when the user saves any changes to the values made at runtime, this is where I update the dictionary and write out the file.

/// <summary>
/// Must override this, this is the bit that matches up the designer properties to the dictionary values
/// </summary>
/// <param name="context"></param>
/// <param name="collection"></param>
/// <returns></returns>
public override SettingsPropertyValueCollection GetPropertyValues(SettingsContext context, SettingsPropertyCollection collection)
{
    //load the file
    if (!_loaded)
    {
         _loaded = true;
         LoadValuesFromFile();
    }

    //collection that will be returned.
    SettingsPropertyValueCollection values = new SettingsPropertyValueCollection();

    //iterate thought the properties we get from the designer, checking to see if the setting is in the dictionary
    foreach (SettingsProperty setting in collection)
    {
        SettingsPropertyValue value = new SettingsPropertyValue(setting);
        value.IsDirty = false;

        //need the type of the value for the strong typing
        var t = Type.GetType(setting.PropertyType.FullName);

        if (SettingsDictionary.ContainsKey(setting.Name))
        {
            value.SerializedValue = SettingsDictionary[setting.Name].value;
            value.PropertyValue = Convert.ChangeType(SettingsDictionary[setting.Name].value, t);
        }
        else //use defaults in the case where there are no settings yet
        {
            value.SerializedValue = setting.DefaultValue;
            value.PropertyValue = Convert.ChangeType(setting.DefaultValue, t);
        }

            values.Add(value);
    }
    return values;
}

/// <summary>
/// Must override this, this is the bit that does the saving to file.  Called when Settings.Save() is called
/// </summary>
/// <param name="context"></param>
/// <param name="collection"></param>
public override void SetPropertyValues(SettingsContext context, SettingsPropertyValueCollection collection)
{
    //grab the values from the collection parameter and update the values in our dictionary.
    foreach (SettingsPropertyValue value in collection)
    {
        var setting = new SettingStruct()
        {
            value = (value.PropertyValue == null ? String.Empty : value.PropertyValue.ToString()),
            name = value.Name,
            serializeAs = value.Property.SerializeAs.ToString()
        };

        if (!SettingsDictionary.ContainsKey(value.Name))
        {
            SettingsDictionary.Add(value.Name, setting);
        }
        else
        {
            SettingsDictionary[value.Name] = setting;
        }
    }

    //now that our local dictionary is up-to-date, save it to disk.
    SaveValuesToFile();
}

Complete solution. So here's the entire class which includes the constructor, Initialize, and helper methods. Feel free to cut/paste slice and dice.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;
using System.Reflection;
using System.Xml.Linq;
using System.IO;

namespace YourCompany.YourProduct
{
    class CustomSettingsProvider : SettingsProvider
    {
        const string NAME = "name";
        const string SERIALIZE_AS = "serializeAs";
        const string CONFIG = "configuration";
        const string USER_SETTINGS = "userSettings";
        const string SETTING = "setting";

        /// <summary>
        /// Loads the file into memory.
        /// </summary>
        public CustomSettingsProvider()
        {
            SettingsDictionary = new Dictionary<string, SettingStruct>();

        }

        /// <summary>
        /// Override.
        /// </summary>
        public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config)
        {
            base.Initialize(ApplicationName, config);
        }

        /// <summary>
        /// Override.
        /// </summary>
        public override string ApplicationName
        {
            get
            {
                return System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.Name;
            }
            set
            {
                //do nothing
            }
        }

        /// <summary>
        /// Must override this, this is the bit that matches up the designer properties to the dictionary values
        /// </summary>
        /// <param name="context"></param>
        /// <param name="collection"></param>
        /// <returns></returns>
        public override SettingsPropertyValueCollection GetPropertyValues(SettingsContext context, SettingsPropertyCollection collection)
        {
            //load the file
            if (!_loaded)
            {
                _loaded = true;
                LoadValuesFromFile();
            }

            //collection that will be returned.
            SettingsPropertyValueCollection values = new SettingsPropertyValueCollection();

            //itterate thought the properties we get from the designer, checking to see if the setting is in the dictionary
            foreach (SettingsProperty setting in collection)
            {
                SettingsPropertyValue value = new SettingsPropertyValue(setting);
                value.IsDirty = false;

                //need the type of the value for the strong typing
                var t = Type.GetType(setting.PropertyType.FullName);

                if (SettingsDictionary.ContainsKey(setting.Name))
                {
                    value.SerializedValue = SettingsDictionary[setting.Name].value;
                    value.PropertyValue = Convert.ChangeType(SettingsDictionary[setting.Name].value, t);
                }
                else //use defaults in the case where there are no settings yet
                {
                    value.SerializedValue = setting.DefaultValue;
                    value.PropertyValue = Convert.ChangeType(setting.DefaultValue, t);
                }

                values.Add(value);
            }
            return values;
        }

        /// <summary>
        /// Must override this, this is the bit that does the saving to file.  Called when Settings.Save() is called
        /// </summary>
        /// <param name="context"></param>
        /// <param name="collection"></param>
        public override void SetPropertyValues(SettingsContext context, SettingsPropertyValueCollection collection)
        {
            //grab the values from the collection parameter and update the values in our dictionary.
            foreach (SettingsPropertyValue value in collection)
            {
                var setting = new SettingStruct()
                {
                    value = (value.PropertyValue == null ? String.Empty : value.PropertyValue.ToString()),
                    name = value.Name,
                    serializeAs = value.Property.SerializeAs.ToString()
                };

                if (!SettingsDictionary.ContainsKey(value.Name))
                {
                    SettingsDictionary.Add(value.Name, setting);
                }
                else
                {
                    SettingsDictionary[value.Name] = setting;
                }
            }

            //now that our local dictionary is up-to-date, save it to disk.
            SaveValuesToFile();
        }

        /// <summary>
        /// Loads the values of the file into memory.
        /// </summary>
        private void LoadValuesFromFile()
        {
            if (!File.Exists(UserConfigPath))
            {
                //if the config file is not where it's supposed to be create a new one.
                CreateEmptyConfig();
            }

            //load the xml
            var configXml = XDocument.Load(UserConfigPath);

            //get all of the <setting name="..." serializeAs="..."> elements.
            var settingElements = configXml.Element(CONFIG).Element(USER_SETTINGS).Element(typeof(Properties.Settings).FullName).Elements(SETTING);

            //iterate through, adding them to the dictionary, (checking for nulls, xml no likey nulls)
            //using "String" as default serializeAs...just in case, no real good reason.
            foreach (var element in settingElements)
            {
                var newSetting = new SettingStruct()
                {
                    name = element.Attribute(NAME) == null ? String.Empty : element.Attribute(NAME).Value,
                    serializeAs = element.Attribute(SERIALIZE_AS) == null ? "String" : element.Attribute(SERIALIZE_AS).Value,
                    value = element.Value ?? String.Empty
                };
                SettingsDictionary.Add(element.Attribute(NAME).Value, newSetting);
            }
        }

        /// <summary>
        /// Creates an empty user.config file...looks like the one MS creates.  
        /// This could be overkill a simple key/value pairing would probably do.
        /// </summary>
        private void CreateEmptyConfig()
        {
            var doc = new XDocument();
            var declaration = new XDeclaration("1.0", "utf-8", "true");
            var config = new XElement(CONFIG);
            var userSettings = new XElement(USER_SETTINGS);
            var group = new XElement(typeof(Properties.Settings).FullName);
            userSettings.Add(group);
            config.Add(userSettings);
            doc.Add(config);
            doc.Declaration = declaration;
            doc.Save(UserConfigPath); 
        }

        /// <summary>
        /// Saves the in memory dictionary to the user config file
        /// </summary>
        private void SaveValuesToFile()
        {
            //load the current xml from the file.
            var import = XDocument.Load(UserConfigPath);

            //get the settings group (e.g. <Company.Project.Desktop.Settings>)
            var settingsSection = import.Element(CONFIG).Element(USER_SETTINGS).Element(typeof(Properties.Settings).FullName);

            //iterate though the dictionary, either updating the value or adding the new setting.
            foreach (var entry in SettingsDictionary)
            {
                var setting = settingsSection.Elements().FirstOrDefault(e => e.Attribute(NAME).Value == entry.Key);
                if (setting == null) //this can happen if a new setting is added via the .settings designer.
                {
                    var newSetting = new XElement(SETTING);
                    newSetting.Add(new XAttribute(NAME, entry.Value.name));
                    newSetting.Add(new XAttribute(SERIALIZE_AS, entry.Value.serializeAs));
                    newSetting.Value = (entry.Value.value ?? String.Empty);
                    settingsSection.Add(newSetting);
                }
                else //update the value if it exists.
                {
                    setting.Value = (entry.Value.value ?? String.Empty);
                }
            }
            import.Save(UserConfigPath);
        }

        /// <summary>
        /// The setting key this is returning must set before the settings are used.
        /// e.g. <c>Properties.Settings.Default.SettingsKey = @"C:\temp\user.config";</c>
        /// </summary>
        private string UserConfigPath
        {
            get
            {
                return Properties.Settings.Default.SettingsKey;
            }

        }

        /// <summary>
        /// In memory storage of the settings values
        /// </summary>
        private Dictionary<string, SettingStruct> SettingsDictionary { get; set; }

        /// <summary>
        /// Helper struct.
        /// </summary>
        internal struct SettingStruct
        {
            internal string name;
            internal string serializeAs;
            internal string value;
        }

        bool _loaded;
    }
}    

You would have to implement your own SettingsProvider to customize the path.

See this Client Settings FAQ

Q: Why is the path so obscure? Is there any way to change/customize it?

A: The path construction algorithm has to meet certain rigorous requirements in terms of security, isolation and robustness. While we tried to make the path as easily discoverable as possible by making use of friendly, application supplied strings, it is not possible to keep the path totally simple without running into issues like collisions with other apps, spoofing etc.

The LocalFileSettingsProvider does not provide a way to change the files in which settings are stored. Note that the provider itself doesn't determine the config file locations in the first place - it is the configuration system. If you need to store the settings in a different location for some reason, the recommended way is to write your own SettingsProvider. This is fairly simple to implement and you can find samples in the .NET 2.0 SDK that show how to do this. Keep in mind however that you may run into the same isolation issues mentioned above .

Here is an easier, briefer alternative to creating a custom settings class: change your app's evidence so that the "url" part is a constant rather than being based on the location of executable. To do this, you need to modify the default AppDomain when the program starts. There are two parts: setting app.config to use your AppDomainManager, and creating an AppDomainManager and HostSecurityManager to customize the Url evidence. Sounds complicated but it's much simpler than creating a custom settings class. This only applies to unsigned assemblies. If you have a signed assembly, it's going to use that evidence instead of the Url. But the good news there is your path will always be constant anyway (as long as the signing key doesn't change).

You can copy the code below and just replace the YourAppName bits.

DefaultAppDomainManager.cs:

using System;
using System.Security;
using System.Security.Policy;

namespace YourAppName
{
    /// <summary>
    /// A least-evil (?) way of customizing the default location of the application's user.config files.
    /// </summary>
    public class CustomEvidenceHostSecurityManager : HostSecurityManager
    {
        public override HostSecurityManagerOptions Flags
        {
            get
            {
                return HostSecurityManagerOptions.HostAssemblyEvidence;
            }
        }

        public override Evidence ProvideAssemblyEvidence(System.Reflection.Assembly loadedAssembly, Evidence inputEvidence)
        {
            if (!loadedAssembly.Location.EndsWith("YourAppName.exe"))
                return base.ProvideAssemblyEvidence(loadedAssembly, inputEvidence);

            // override the full Url used in Evidence to just "YourAppName.exe" so it remains the same no matter where the exe is located
            var zoneEvidence = inputEvidence.GetHostEvidence<Zone>();
            return new Evidence(new EvidenceBase[] { zoneEvidence, new Url("YourAppName.exe") }, null);
        }
    }

    public class DefaultAppDomainManager : AppDomainManager
    {
        private CustomEvidenceHostSecurityManager hostSecurityManager;
        public override void InitializeNewDomain(AppDomainSetup appDomainInfo)
        {
            base.InitializeNewDomain(appDomainInfo);

            hostSecurityManager = new CustomEvidenceHostSecurityManager();
        }

        public override HostSecurityManager HostSecurityManager
        {
            get
            {
                return hostSecurityManager;
            }
        }
    }
}

app.config excerpt:

<runtime>
    <appDomainManagerType value="YourAppName.DefaultAppDomainManager" />
    <appDomainManagerAssembly value="DefaultAppDomainManager, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
</runtime>

Building on Chucks excellent answer:

Implement a new partial class based on Settings.Designer.cs, so the Settings Designer does not wipe out the attribute when changes are made:

namespace Worker.Properties
{
    [System.Configuration.SettingsProvider(
        typeof(SettingsProviders.DllFileSettingsProvider<Settings>))]
    internal sealed partial class Settings
    {

    }
}

I created the following class that can be put in an external project. It allows the config to be project.dll.config. By Inheriting and Overriding ConfigPath allows any path you like. I also added support for reading System.Collections.Specialized.StringCollection. This version is for Application settings.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;
using System.Reflection;
using System.Xml.Linq;
using System.IO;


//http://stackoverflow.com/questions/2265271/custom-path-of-the-user-config
namespace SettingsProviders
{
    public  class DllFileSettingsProvider<Properties_Settings> : SettingsProvider where Properties_Settings : new() 
    {
        const string NAME = "name";
        const string SERIALIZE_AS = "serializeAs";
        const string CONFIG = "configuration";
        const string APPLICATION_SETTINGS = "applicationSettings";
        const string SETTING = "setting";

        /// <summary>
        /// Loads the file into memory.
        /// </summary>
        public DllFileSettingsProvider()
        {
            SettingsDictionary = new Dictionary<string, SettingStruct>();

        }

        /// <summary>
        /// Override.
        /// </summary>
        public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config)
        {
            base.Initialize(ApplicationName, config);
        }

        /// <summary>
        /// Override.
        /// </summary>
        public override string ApplicationName
        {
            get
            {
                return System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.Name;
            }
            set
            {
                //do nothing
            }
        }

        /// <summary>
        /// Must override this, this is the bit that matches up the designer properties to the dictionary values
        /// </summary>
        /// <param name="context"></param>
        /// <param name="collection"></param>
        /// <returns></returns>
        public override SettingsPropertyValueCollection GetPropertyValues(SettingsContext context, SettingsPropertyCollection collection)
        {
            //load the file
            if (!_loaded)
            {
                _loaded = true;
                LoadValuesFromFile();
            }

            //collection that will be returned.
            SettingsPropertyValueCollection values = new SettingsPropertyValueCollection();

            //itterate thought the properties we get from the designer, checking to see if the setting is in the dictionary
            foreach (SettingsProperty setting in collection)
            {
                SettingsPropertyValue value = new SettingsPropertyValue(setting);
                value.IsDirty = false;

                //need the type of the value for the strong typing
                var t = Type.GetType(setting.PropertyType.FullName);

                if (setting.PropertyType == typeof(System.Collections.Specialized.StringCollection))
                {
                    var xml = SettingsDictionary[setting.Name].value;
                    var stringReader = new System.IO.StringReader(xml);
                    var xmlreader = System.Xml.XmlReader.Create(stringReader);
                    var ser = new System.Xml.Serialization.XmlSerializer(typeof(System.Collections.Specialized.StringCollection));
                    var obj = ser.Deserialize(xmlreader);
                    var col = (System.Collections.Specialized.StringCollection)obj;
                    value.PropertyValue = col;
                }
                else if (SettingsDictionary.ContainsKey(setting.Name))
                {
                    value.SerializedValue = SettingsDictionary[setting.Name].value;
                    value.PropertyValue = Convert.ChangeType(SettingsDictionary[setting.Name].value, t);
                }
                else //use defaults in the case where there are no settings yet
                {
                    value.SerializedValue = setting.DefaultValue;
                    value.PropertyValue = Convert.ChangeType(setting.DefaultValue, t);
                }

                values.Add(value);
            }
            return values;
        }

        /// <summary>
        /// Must override this, this is the bit that does the saving to file.  Called when Settings.Save() is called
        /// </summary>
        /// <param name="context"></param>
        /// <param name="collection"></param>
        public override void SetPropertyValues(SettingsContext context, SettingsPropertyValueCollection collection)
        {
            //grab the values from the collection parameter and update the values in our dictionary.
            foreach (SettingsPropertyValue value in collection)
            {
                var setting = new SettingStruct()
                {
                    value = (value.PropertyValue == null ? String.Empty : value.PropertyValue.ToString()),
                    name = value.Name,
                    serializeAs = value.Property.SerializeAs.ToString()
                };

                if (!SettingsDictionary.ContainsKey(value.Name))
                {
                    SettingsDictionary.Add(value.Name, setting);
                }
                else
                {
                    SettingsDictionary[value.Name] = setting;
                }
            }

            //now that our local dictionary is up-to-date, save it to disk.
            SaveValuesToFile();
        }

        /// <summary>
        /// Loads the values of the file into memory.
        /// </summary>
        private void LoadValuesFromFile()
        {
            if (!File.Exists(ConfigPath))
            {
                //if the config file is not where it's supposed to be create a new one.
                throw new Exception("Config file not found: " + ConfigPath);
            }

            //load the xml
            var configXml = XDocument.Load(ConfigPath);

            //get all of the <setting name="..." serializeAs="..."> elements.
            var settingElements = configXml.Element(CONFIG).Element(APPLICATION_SETTINGS).Element(typeof(Properties_Settings).FullName).Elements(SETTING);

            //iterate through, adding them to the dictionary, (checking for nulls, xml no likey nulls)
            //using "String" as default serializeAs...just in case, no real good reason.
            foreach (var element in settingElements)
            {

                var newSetting = new SettingStruct()
                {
                    name = element.Attribute(NAME) == null ? String.Empty : element.Attribute(NAME).Value,
                    serializeAs = element.Attribute(SERIALIZE_AS) == null ? "String" : element.Attribute(SERIALIZE_AS).Value ,
                    value = element.Value ?? String.Empty
                };

                if (newSetting.serializeAs == "Xml")
                {
                    var e = (XElement)element.Nodes().First();
                    newSetting.value = e.LastNode.ToString() ?? String.Empty;
                };

                SettingsDictionary.Add(element.Attribute(NAME).Value, newSetting);
            }
        }

        /// <summary>
        /// Creates an empty user.config file...looks like the one MS creates.  
        /// This could be overkill a simple key/value pairing would probably do.
        /// </summary>
        private void CreateEmptyConfig()
        {
            var doc = new XDocument();
            var declaration = new XDeclaration("1.0", "utf-8", "true");
            var config = new XElement(CONFIG);
            var userSettings = new XElement(APPLICATION_SETTINGS);
            var group = new XElement(typeof(Properties_Settings).FullName);
            userSettings.Add(group);
            config.Add(userSettings);
            doc.Add(config);
            doc.Declaration = declaration;
            doc.Save(ConfigPath);
        }

        /// <summary>
        /// Saves the in memory dictionary to the user config file
        /// </summary>
        private void SaveValuesToFile()
        {
            //load the current xml from the file.
            var import = XDocument.Load(ConfigPath);

            //get the settings group (e.g. <Company.Project.Desktop.Settings>)
            var settingsSection = import.Element(CONFIG).Element(APPLICATION_SETTINGS).Element(typeof(Properties_Settings).FullName);

            //iterate though the dictionary, either updating the value or adding the new setting.
            foreach (var entry in SettingsDictionary)
            {
                var setting = settingsSection.Elements().FirstOrDefault(e => e.Attribute(NAME).Value == entry.Key);
                if (setting == null) //this can happen if a new setting is added via the .settings designer.
                {
                    var newSetting = new XElement(SETTING);
                    newSetting.Add(new XAttribute(NAME, entry.Value.name));
                    newSetting.Add(new XAttribute(SERIALIZE_AS, entry.Value.serializeAs));
                    newSetting.Value = (entry.Value.value ?? String.Empty);
                    settingsSection.Add(newSetting);
                }
                else //update the value if it exists.
                {
                    setting.Value = (entry.Value.value ?? String.Empty);
                }
            }
            import.Save(ConfigPath);
        }

        /// <summary>
        /// The setting key this is returning must set before the settings are used.
        /// e.g. <c>Properties.Settings.Default.SettingsKey = @"C:\temp\user.config";</c>
        /// </summary>
        public virtual string ConfigPath
        {
            get
            {
                var name = new Properties_Settings().GetType().Module.Name + ".config";
                if (System.IO.File.Exists(name)==false)
                {
                    System.Diagnostics.Trace.WriteLine("config file NOT found:" + name);
                }
                System.Diagnostics.Trace.WriteLine("config file found:" + name);

                return name;
               // return Properties.Settings.Default.SettingsKey;
            }

        }

        /// <summary>
        /// In memory storage of the settings values
        /// </summary>
        internal Dictionary<string, SettingStruct> SettingsDictionary { get; set; }

        /// <summary>
        /// Helper struct.
        /// </summary>
        internal struct SettingStruct
        {
            internal string name;
            internal string serializeAs;
            internal string value;
        }

        bool _loaded;
    }
}

Make sure dependent projects include the project.dll.config file by add a post-build event:

copy $(SolutionDir)Worker\$(OutDir)Worker.dll.config $(TargetDir) /y