如何在运行时更新(添加/修改/删除)web.config的AppSettings部分中的键

Question

我喜欢更新运行时AppSettings部分中定义的键/值Web.config.但是我不想实际将它们保存到Web.config文件中.

我有一个巨大的Web应用程序,包含许多模块,DLL和源代码文件.的关键信息的一束从数据库配置,加密密钥,用户名和范围为web服务的密码保存在AppSettings所述的部分web.config文件.最近的项目要求需要我将这些值移出web.config并保存在安全存储中.

我已经在外部位置保护了这些值,我可以在应用程序启动时读回它们.

这是示例代码.

Global.asax中

public class Global: System.Web.HttpApplication {
    protected void Application_Start(object sender, EventArgs e) {
        Dictionary<string, string> secureConfig = new Dictionary<string,string>{};

        // --------------------------------------------------------------------
        // Here I read and decrypt keys and add them to secureConfig dictionary
        // To test assume the following line is a key stored in secure sotrage.
        //secureConfig = SecureConfig.LoadConfig();
        secureConfig.Add("ACriticalKey","VeryCriticalValue");
        // --------------------------------------------------------------------

        foreach (KeyValuePair<string, string> item in secureConfig) {
            ConfigurationManager.AppSettings.Add(item.Key, item.Value);
        }
    }
}

正如您可能已经注意到,将AppSettings多个编程团队创建的大量代码中的引用更改为从我这里读取其设置是不可行的,secureConfig dictionary另一方面,我不应将这些值保存在web.configWeb管理员和操作员可用的文件中,系统管理员和云管理员.

为了让程序员的生活更轻松,我想让他们将他们的值添加到开发期间的AppSettings部分web.config,但是他们将从那里删除并在部署期间安全存储,但是这些值应该可以透明地编程,因为它们仍在AppSettings部分.

问题:如何AppSettings在运行时添加值,以便程序可以使用它ConfigurationManager.AppSettings["ACriticalKey"]来读取它们"VeryCriticalValue"而不将它们保存在Web.Config中？

请注意:ConfigurationManager.AppSettings.Add(item.Key, item.Value);给我ConfigurationErrorsException留言The configuration is read only.

请注意:最好是某些设置应该AppSettings像以前一样保持不变

Answer 1

我知道这是一个老问题,但我遇到了同样的问题,我发现Set的工作方式与Add相同,并且不会抛出异常,所以只需将Add替换为Set,如下所示:

ConfigurationManager.AppSettings.Set(item.Key, item.Value);

Answer 2

您需要利用 WebConfigurationManager.OpenWebConfiguration()

Configuration config = WebConfigurationManager.OpenWebConfiguration(HttpContext.Current.Request.ApplicationPath);
config.AppSettings.Settings.Remove("Variable");
config.AppSettings.Settings.Add("Variable", "valyue");
config.Save();

Answer 3

感谢 nkvu 将我引导到他的第一个链接，该链接又将我发送到Williarob的帖子“覆盖配置管理器”，我设法找到了我的问题的解决方案。

提到的博客文章介绍了如何从另一个 XML 文件读取设置，它适用于窗口应用程序和 Web 应用程序（对配置文件名和路径进行一些修改）。尽管这篇博客写于 2010 年，但它仍然可以在 .NET4 上正常运行，没有任何问题。

然而，当我要从安全设备读取我的配置时，我简化了该类，以下是如何使用Williarob提供的类

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Configuration.Internal;
using System.Linq;
using System.Reflection;

namespace Williablog.Core.Configuration {

    public sealed class ConfigSystem: IInternalConfigSystem {
        private static IInternalConfigSystem clientConfigSystem;

        private object appsettings;

        private object connectionStrings;

        /// <summary>
        /// Re-initializes the ConfigurationManager, allowing us to merge in the settings from Core.Config
        /// </summary>
        public static void Install() {
            FieldInfo[] fiStateValues = null;
            Type tInitState = typeof(System.Configuration.ConfigurationManager).GetNestedType("InitState", BindingFlags.NonPublic);

            if (null != tInitState) {
                fiStateValues = tInitState.GetFields();
            }

            FieldInfo fiInit = typeof(System.Configuration.ConfigurationManager).GetField("s_initState", BindingFlags.NonPublic | BindingFlags.Static);
            FieldInfo fiSystem = typeof(System.Configuration.ConfigurationManager).GetField("s_configSystem", BindingFlags.NonPublic | BindingFlags.Static);

            if (fiInit != null && fiSystem != null && null != fiStateValues) {
                fiInit.SetValue(null, fiStateValues[1].GetValue(null));
                fiSystem.SetValue(null, null);
            }

            ConfigSystem confSys = new ConfigSystem();
            Type configFactoryType = Type.GetType("System.Configuration.Internal.InternalConfigSettingsFactory, System.Configuration, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", true);
            IInternalConfigSettingsFactory configSettingsFactory = (IInternalConfigSettingsFactory) Activator.CreateInstance(configFactoryType, true);
            configSettingsFactory.SetConfigurationSystem(confSys, false);

            Type clientConfigSystemType = Type.GetType("System.Configuration.ClientConfigurationSystem, System.Configuration, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", true);
            clientConfigSystem = (IInternalConfigSystem) Activator.CreateInstance(clientConfigSystemType, true);
        }

        #region IInternalConfigSystem Members
        public object GetSection(string configKey) {
            // get the section from the default location (web.config or app.config)
            object section = clientConfigSystem.GetSection(configKey);

            switch (configKey) {
                case "appSettings":
                    // Return cached version if exists
                    if (this.appsettings != null) {
                        return this.appsettings;
                    }

                    // create a new collection because the underlying collection is read-only
                    var cfg = new NameValueCollection();

                    // If an AppSettings section exists in Web.config, read and add values from it
                    if (section is NameValueCollection) {
                        NameValueCollection localSettings = (NameValueCollection) section;
                        foreach (string key in localSettings) {
                            cfg.Add(key, localSettings[key]);
                        }
                    }

                    // --------------------------------------------------------------------
                    // Here I read and decrypt keys and add them to secureConfig dictionary
                    // To test assume the following line is a key stored in secure sotrage.
                    //secureConfig = SecureConfig.LoadConfig();
                    secureConfig.Add("ACriticalKey", "VeryCriticalValue");
                    // --------------------------------------------------------------------                        
                    foreach (KeyValuePair<string, string> item in secureConfig) {
                        if (cfg.AllKeys.Contains(item.Key)) {
                            cfg[item.Key] = item.Value;
                        } else {
                            cfg.Add(item.Key, item.Value);
                        }
                    }
                    // --------------------------------------------------------------------                        


                    // Cach the settings for future use
                    this.appsettings = cfg;
                    // return the merged version of the items from secure storage and appsettings
                    section = this.appsettings;
                    break;

                case "connectionStrings":
                    // Return cached version if exists
                    if (this.connectionStrings != null) {
                        return this.connectionStrings;
                    }

                    // create a new collection because the underlying collection is read-only
                    ConnectionStringsSection connectionStringsSection = new ConnectionStringsSection();

                    // copy the existing connection strings into the new collection
                    foreach (ConnectionStringSettings connectionStringSetting in ((ConnectionStringsSection) section).ConnectionStrings) {
                        connectionStringsSection.ConnectionStrings.Add(connectionStringSetting);
                    }

                    // --------------------------------------------------------------------
                    // Again Load connection strings from secure storage and merge like below
                    // connectionStringsSection.ConnectionStrings.Add(connectionStringSetting);
                    // --------------------------------------------------------------------                        

                    // Cach the settings for future use
                    this.connectionStrings = connectionStringsSection;
                    // return the merged version of the items from secure storage and appsettings
                    section = this.connectionStrings;
                    break;
            }

            return section;
        }

        public void RefreshConfig(string sectionName) {
            if (sectionName == "appSettings") {
                this.appsettings = null;
            }

            if (sectionName == "connectionStrings") {
                this.connectionStrings = null;
            }

            clientConfigSystem.RefreshConfig(sectionName);
        }

        public bool SupportsUserConfig { get { return clientConfigSystem.SupportsUserConfig; } }

        #endregion
    }
}

要安装此版本（或配置覆盖的原始版本），请将以下行添加到您的 Global. Application_Start 中的类 (Global.asax.cs)

Williablog.Core.Configuration.ConfigSystem .Install();

像下面这样：

public class Global: System.Web.HttpApplication {

    //...

    #region protected void Application_Start(...)
    protected void Application_Start(object sender, EventArgs e) {
        Williablog.Core.Configuration.ConfigSystem .Install();

        //...

    }
    #endregion

    //...

}