c# - 当存储的数据类型发生变化时，如何升级 Settings.settings？

Question

我有一个在用户设置中存储对象集合的应用程序，并通过 ClickOnce 进行部署。下一个版本的应用程序对存储的对象进行了修改。例如，以前版本的类型是:

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

新版本的类型是:

public class Person
{
    public string Name { get; set; }
    public DateTime DateOfBirth { get; set; }
}

显然，ApplicationSettingsBase.Upgrade 不知道如何执行升级，因为 Age 需要使用 (age) => DateTime.Now.AddYears(-age)，因此只会升级 Name 属性，而 DateOfBirth 的值将仅为 Default(DateTime)。

所以我想提供一个升级例程，通过覆盖 ApplicationSettingsBase.Upgrade，它会根据需要转换值。但是我遇到了三个问题:

1. 当尝试使用 ApplicationSettingsBase.GetPreviousVersion 访问以前版本的值时，返回值将是当前版本的对象，它没有 Age 属性并且有一个空的 DateOfBirth 属性 (因为它无法将 Age 反序列化为 DateOfBirth)。
2. 我无法找到一种方法来确定我要升级的应用程序版本。如果有一个从v1到v2的升级过程和一个从v2到v3的过程，如果用户是从v1升级到v3，我需要依次运行两个升级过程，但是如果用户是从v2升级，我只需要运行第二个升级程序。
3. 即使我知道应用程序的以前版本是什么，并且我可以在他们以前的结构中访问用户设置(比如通过获取原始 XML 节点)，如果我想链式升级过程(如问题中所述2)，我应该在哪里存储中间值？如果从 v2 升级到 v3，升级过程将从 v2 读取旧值并将它们直接写入 v3 中的强类型设置包装类。但是，如果从 v1 升级，我应该把 v1 到 v2 升级过程的结果放在哪里，因为应用程序只有 v3 的包装类？

我认为如果升级代码直接在 user.config 文件上执行转换，我可以避免所有这些问题，但我发现没有简单的方法来获取以前版本的 user.config 的位置，因为 LocalFileSettingsProvider.GetPreviousConfigFileName(bool) 是私有(private)方法。

有没有人有用于升级在应用程序版本之间更改类型的用户设置的 ClickOnce 兼容解决方案，最好是可以支持跳过版本的解决方案(例如，从 v1 升级到 v3 而无需用户安装 v2)？

Answer 1

我最终使用了一种更复杂的方式来进行升级，即从用户设置文件中读取原始 XML，然后运行一系列升级例程，将数据重构为下一个新版本中的预期方式。此外，由于我在 ClickOnce 的 ApplicationDeployment.CurrentDeployment.IsFirstRun 属性中发现的错误(您可以查看 Microsoft Connect 反馈 here )，我不得不使用自己的 IsFirstRun 设置来了解何时执行升级。整个系统对我来说工作得很好(但由于一些非常顽固的障碍，它是用血和汗水制成的)。忽略注释标记我的应用程序特定的内容，而不是升级系统的一部分。

using System;
using System.Collections.Specialized;
using System.Configuration;
using System.Xml;
using System.IO;
using System.Linq;
using System.Windows.Forms;
using System.Reflection;
using System.Text;
using MyApp.Forms;
using MyApp.Entities;

namespace MyApp.Properties
{
    public sealed partial class Settings
    {
        private static readonly Version CurrentVersion = Assembly.GetExecutingAssembly().GetName().Version;

        private Settings()
        {
            InitCollections();  // ignore
        }

        public override void Upgrade()
        {
            UpgradeFromPreviousVersion();
            BadDataFiles = new StringCollection();  // ignore
            UpgradePerformed = true; // this is a boolean value in the settings file that is initialized to false to indicate that settings file is brand new and requires upgrading
            InitCollections();  // ignore
            Save();
        }

        // ignore
        private void InitCollections()
        {
            if (BadDataFiles == null)
                BadDataFiles = new StringCollection();

            if (UploadedGames == null)
                UploadedGames = new StringDictionary();

            if (SavedSearches == null)
                SavedSearches = SavedSearchesCollection.Default;
        }

        private void UpgradeFromPreviousVersion()
        {
            try
            {
                // This works for both ClickOnce and non-ClickOnce applications, whereas
                // ApplicationDeployment.CurrentDeployment.DataDirectory only works for ClickOnce applications
                DirectoryInfo currentSettingsDir = new FileInfo(ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal).FilePath).Directory;

                if (currentSettingsDir == null)
                    throw new Exception("Failed to determine the location of the settings file.");

                if (!currentSettingsDir.Exists)
                    currentSettingsDir.Create();

                // LINQ to Objects for .NET 2.0 courtesy of LINQBridge (linqbridge.googlecode.com)
                var previousSettings = (from dir in currentSettingsDir.Parent.GetDirectories()
                                        let dirVer = new { Dir = dir, Ver = new Version(dir.Name) }
                                        where dirVer.Ver < CurrentVersion
                                        orderby dirVer.Ver descending
                                        select dirVer).FirstOrDefault();

                if (previousSettings == null)
                    return;

                XmlElement userSettings = ReadUserSettings(previousSettings.Dir.GetFiles("user.config").Single().FullName);
                userSettings = SettingsUpgrader.Upgrade(userSettings, previousSettings.Ver);
                WriteUserSettings(userSettings, currentSettingsDir.FullName + @"\user.config", true);

                Reload();
            }
            catch (Exception ex)
            {
                MessageBoxes.Alert(MessageBoxIcon.Error, "There was an error upgrading the the user settings from the previous version. The user settings will be reset.\n\n" + ex.Message);
                Default.Reset();
            }
        }

        private static XmlElement ReadUserSettings(string configFile)
        {
            // PreserveWhitespace required for unencrypted files due to https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=352591
            var doc = new XmlDocument { PreserveWhitespace = true };
            doc.Load(configFile);
            XmlNode settingsNode = doc.SelectSingleNode("configuration/userSettings/MyApp.Properties.Settings");
            XmlNode encryptedDataNode = settingsNode["EncryptedData"];
            if (encryptedDataNode != null)
            {
                var provider = new RsaProtectedConfigurationProvider();
                provider.Initialize("userSettings", new NameValueCollection());
                return (XmlElement)provider.Decrypt(encryptedDataNode);
            }
            else
            {
                return (XmlElement)settingsNode;
            }
        }

        private static void WriteUserSettings(XmlElement settingsNode, string configFile, bool encrypt)
        {
            XmlDocument doc;
            XmlNode MyAppSettings;

            if (encrypt)
            {
                var provider = new RsaProtectedConfigurationProvider();
                provider.Initialize("userSettings", new NameValueCollection());
                XmlNode encryptedSettings = provider.Encrypt(settingsNode);
                doc = encryptedSettings.OwnerDocument;
                MyAppSettings = doc.CreateElement("MyApp.Properties.Settings").AppendNewAttribute("configProtectionProvider", provider.GetType().Name);
                MyAppSettings.AppendChild(encryptedSettings);
            }
            else
            {
                doc = settingsNode.OwnerDocument;
                MyAppSettings = settingsNode;
            }

            doc.RemoveAll();
            doc.AppendNewElement("configuration")
                .AppendNewElement("userSettings")
                .AppendChild(MyAppSettings);

            using (var writer = new XmlTextWriter(configFile, Encoding.UTF8) { Formatting = Formatting.Indented, Indentation = 4 })
                doc.Save(writer);
        }

        private static class SettingsUpgrader
        {
            private static readonly Version MinimumVersion = new Version(0, 2, 1, 0);

            public static XmlElement Upgrade(XmlElement userSettings, Version oldSettingsVersion)
            {
                if (oldSettingsVersion < MinimumVersion)
                    throw new Exception("The minimum required version for upgrade is " + MinimumVersion);

                var upgradeMethods = from method in typeof(SettingsUpgrader).GetMethods(BindingFlags.Static | BindingFlags.NonPublic)
                                     where method.Name.StartsWith("UpgradeFrom_")
                                     let methodVer = new { Version = new Version(method.Name.Substring(12).Replace('_', '.')), Method = method }
                                     where methodVer.Version >= oldSettingsVersion && methodVer.Version < CurrentVersion
                                     orderby methodVer.Version ascending 
                                     select methodVer;

                foreach (var methodVer in upgradeMethods)
                {
                    try
                    {
                        methodVer.Method.Invoke(null, new object[] { userSettings });
                    }
                    catch (TargetInvocationException ex)
                    {
                        throw new Exception(string.Format("Failed to upgrade user setting from version {0}: {1}",
                                                          methodVer.Version, ex.InnerException.Message), ex.InnerException);
                    }
                }

                return userSettings;
            }

            private static void UpgradeFrom_0_2_1_0(XmlElement userSettings)
            {
                // ignore method body - put your own upgrade code here

                var savedSearches = userSettings.SelectNodes("//SavedSearch");

                foreach (XmlElement savedSearch in savedSearches)
                {
                    string xml = savedSearch.InnerXml;
                    xml = xml.Replace("IRuleOfGame", "RuleOfGame");
                    xml = xml.Replace("Field>", "FieldName>");
                    xml = xml.Replace("Type>", "Comparison>");
                    savedSearch.InnerXml = xml;


                    if (savedSearch["Name"].GetTextValue() == "Tournament")
                        savedSearch.AppendNewElement("ShowTournamentColumn", "true");
                    else
                        savedSearch.AppendNewElement("ShowTournamentColumn", "false");
                }
            }
        }
    }
}

使用了以下自定义扩展方法和辅助类:

using System;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Xml;


namespace MyApp
{
    public static class ExtensionMethods
    {
        public static XmlNode AppendNewElement(this XmlNode element, string name)
        {
            return AppendNewElement(element, name, null);
        }
        public static XmlNode AppendNewElement(this XmlNode element, string name, string value)
        {
            return AppendNewElement(element, name, value, null);
        }
        public static XmlNode AppendNewElement(this XmlNode element, string name, string value, params KeyValuePair<string, string>[] attributes)
        {
            XmlDocument doc = element.OwnerDocument ?? (XmlDocument)element;
            XmlElement addedElement = doc.CreateElement(name);

            if (value != null)
                addedElement.SetTextValue(value);

            if (attributes != null)
                foreach (var attribute in attributes)
                    addedElement.AppendNewAttribute(attribute.Key, attribute.Value);

            element.AppendChild(addedElement);

            return addedElement;
        }
        public static XmlNode AppendNewAttribute(this XmlNode element, string name, string value)
        {
            XmlAttribute attr = element.OwnerDocument.CreateAttribute(name);
            attr.Value = value;
            element.Attributes.Append(attr);
            return element;
        }
    }
}

namespace MyApp.Forms
{
    public static class MessageBoxes
    {
        private static readonly string Caption = "MyApp v" + Application.ProductVersion;

        public static void Alert(MessageBoxIcon icon, params object[] args)
        {
            MessageBox.Show(GetMessage(args), Caption, MessageBoxButtons.OK, icon);
        }
        public static bool YesNo(MessageBoxIcon icon, params object[] args)
        {
            return MessageBox.Show(GetMessage(args), Caption, MessageBoxButtons.YesNo, icon) == DialogResult.Yes;
        }

        private static string GetMessage(object[] args)
        {
            if (args.Length == 1)
            {
                return args[0].ToString();
            }
            else
            {
                var messegeArgs = new object[args.Length - 1];
                Array.Copy(args, 1, messegeArgs, 0, messegeArgs.Length);
                return string.Format(args[0] as string, messegeArgs);
            }

        }
    }
}

下面的Main方法被用来让系统工作:

[STAThread]
static void Main()
{
        // Ensures that the user setting's configuration system starts in an encrypted mode, otherwise an application restart is required to change modes.
        Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
        SectionInformation sectionInfo = config.SectionGroups["userSettings"].Sections["MyApp.Properties.Settings"].SectionInformation;
        if (!sectionInfo.IsProtected)
        {
            sectionInfo.ProtectSection(null);
            config.Save();
        }

        if (Settings.Default.UpgradePerformed == false)
            Settings.Default.Upgrade();

        Application.Run(new frmMain());
}

我欢迎任何意见、批评、建议或改进。我希望这对某个地方的人有所帮助。