.NET Core 2.0迁移技巧之web.config配置文件

大家都知道.NET Core现在不再支持原来的web.config配置文件了，取而代之的是json或xml配置文件。官方推荐的项目配置方式是使用appsettings.json配置文件，这对现有一些重度使用web.cofig配置的项目迁移可能是不可接受的。

但是好消息是，我们是可以直接在.NET Core 2.0项目种利用上现有的web.config的。

迁移方法

　　　　1.首先在解决方案中引入System.Configuration.ConfigurationManager,只有引入它才可以让我们已有的读取web.config代码起作用.

　　　　2. 导入web.config文件到项目根目录，并将名称修改为app.config. 因为.NET Core的项目本质是控制台应用，所以ConfigurationManager的API会去默认读取app.config配置文件，而不是web.config配置文件。

　　　　3.去除config中和需要的配置无关的内容，主要是<system.web>,<system.webServer>和<system.codedom>等典型asp.net标签。

　　　　移除前：

<?xml version="1.0" encoding="utf-8"?><configuration>

  <configSections>
      <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
      <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-WebApplication24-20170824065102.mdf;Initial Catalog=aspnet-WebApplication24-20170824065102;Integrated Security=True"providerName="System.Data.SqlClient" />
  </connectionStrings>  <appSettings><add key="webpages:Version" value="3.0.0.0" /><add key="webpages:Enabled" value="false" /><add key="ClientValidationEnabled" value="true" /><add key="UnobtrusiveJavaScriptEnabled" value="true" /><add key="MyKey" value="true"/></appSettings><system.web><compilation debug="true" targetFramework="4.7" /><httpRuntime targetFramework="4.7" /><httpModules><add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" /></httpModules></system.web><runtime><assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="Newtonsoft.Json" culture="neutral" publicKeyToken="30ad4fe6b2a6aeed" /><bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" /></dependentAssembly><dependentAssembly><assemblyIdentity name="System.Web.Optimization" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="1.1.0.0" /></dependentAssembly><dependentAssembly><assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234" /></dependentAssembly><dependentAssembly><assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" /></dependentAssembly><dependentAssembly><assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" /></dependentAssembly><dependentAssembly><assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" /></dependentAssembly></assemblyBinding></runtime><system.webServer><validation validateIntegratedModeConfiguration="false" /><modules><remove name="ApplicationInsightsWebTracking" /><add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" preCondition="managedHandler" /></modules></system.webServer><system.codedom><compilers><compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701" /><compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+" /></compilers></system.codedom></configuration>

　　修改后：

<?xml version="1.0" encoding="utf-8"?><configuration><configSections><!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --><section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /></configSections><connectionStrings><add name="DefaultConnection" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-WebApplication24-20170824065102.mdf;Initial Catalog=aspnet-WebApplication24-20170824065102;Integrated Security=True"providerName="System.Data.SqlClient" /></connectionStrings><appSettings><add key="webpages:Version" value="3.0.0.0" /><add key="webpages:Enabled" value="false" /><add key="ClientValidationEnabled" value="true" /><add key="UnobtrusiveJavaScriptEnabled" value="true" /><add key="MyKey" value="true"/></appSettings></configuration>

　　　　4.测试原ASP.NET代码，查看读取配置值

using System.Configuration;namespace WebConfigTest.Configuration
{public class ConfigurationService{public static bool GetConfigValue(string key){var result = false;var val= ConfigurationManager.AppSettings[key];if (val != null){result = bool.Parse(val);}return result;}}
}

打个断点，看下读取配置值是否正确：