我有时或有时没遇到这个错误（有时候app运行正常），但现在它一次又一次地给我错误。 我在本地主机上运行我的应用程序。以下是错误详细信息。 我不确定为什么我会遇到这个错误，我想我做错了什么。由于这个错误，我被困在我的项目的进一步工作。
建立与SQL Server的连接时发生与网络相关或特定于实例的错误。服务器未找到或无法访问。验证实例名称是否正确，以及SQL Server是否配置为允许远程连接。 （提供程序：SQL网络接口，错误：26 - 查找指定的服务器/实例时出错）
的Web.config：
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
<sectionGroup name="dotNetOpenAuth" type="DotNetOpenAuth.Configuration.DotNetOpenAuthSection, DotNetOpenAuth.Core">
<section name="messaging" type="DotNetOpenAuth.Configuration.MessagingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
<section name="reporting" type="DotNetOpenAuth.Configuration.ReportingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
<section name="openid" type="DotNetOpenAuth.Configuration.OpenIdElement, DotNetOpenAuth.OpenId" requirePermission="false" allowLocation="true" /><section name="oauth" type="DotNetOpenAuth.Configuration.OAuthElement, DotNetOpenAuth.OAuth" requirePermission="false" allowLocation="true" /></sectionGroup></configSections>
<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=mydb;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\mydb.mdf" providerName="System.Data.SqlClient" />
</connectionStrings>
<appSettings>
<add key="webpages:Version" value="3.0.0.0" /> <!--i have made new version from 2.0.0.0 to 3-->
<add key="webpages:Enabled" value="false" />
<add key="PreserveLoginUrl" value="true" />
<add key="ClientValidationEnabled" value="true" />
<add key="UnobtrusiveJavaScriptEnabled" value="true" />
</appSettings>
<system.web>
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" />
<authentication mode="Forms">
<forms loginUrl="~/Account/Login" timeout="2880" />
</authentication>
<pages>
<namespaces>
<add namespace="System.Web.Helpers" />
<add namespace="System.Web.Mvc" />
<add namespace="System.Web.Mvc.Ajax" />
<add namespace="System.Web.Mvc.Html" />
<add namespace="System.Web.Optimization" />
<add namespace="System.Web.Routing" />
<add namespace="System.Web.WebPages" />
</namespaces>
</pages>
</system.web>
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<handlers>
<remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
<remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
<remove name="ExtensionlessUrlHandler-Integrated-4.0" />
<add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
<add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
</system.webServer>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.Core" publicKeyToken="2780ccd10d57b246" />
<bindingRedirect oldVersion="0.0.0.0-4.3.0.0" newVersion="4.3.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.AspNet" publicKeyToken="2780ccd10d57b246" />
<bindingRedirect oldVersion="0.0.0.0-4.3.0.0" newVersion="4.3.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="3.0.0.0" /><!--i have made new version from 2.0.0.0 to 3-->
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-5.2.2.0" newVersion="5.2.2.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-1.6.5135.21930" newVersion="1.6.5135.21930" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System" publicKeyToken="b77a5c561934e089" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Antlr3.Runtime" publicKeyToken="eb42632606e9261f" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-3.5.0.2" newVersion="3.5.0.2" />
</dependentAssembly>
</assemblyBinding>
<!--This prevents the Windows Event Log from frequently logging that HMAC1 is being used (when the other party needs it). <legacyHMACWarning enabled="0" /> When targeting ASP.NET MVC 3, this assemblyBinding makes MVC 1 and 2 references relink
to MVC 3 so libraries such as DotNetOpenAuth that compile against MVC 1 will work with it.-->
</runtime>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="v11.0" />
</parameters>
</defaultConnectionFactory>
<providers>
<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
</entityFramework>
<system.net>
<defaultProxy enabled="true" />
<settings>
<!--This setting causes .NET to check certificate revocation lists (CRL)
before trusting HTTPS certificates. But this setting tends to not
be allowed in shared hosting environments.-->
<servicePointManager checkCertificateRevocationList="true" />
</settings>
</system.net><dotNetOpenAuth>
<messaging>
<untrustedWebRequest>
<whitelistHosts>
<!--Uncomment to enable communication with localhost (should generally not activate in production!)-->
<add name="localhost" />
</whitelistHosts>
</untrustedWebRequest>
</messaging>
<!--Allow DotNetOpenAuth to publish usage statistics to library authors to improve the library.-->
<!--<reporting enabled="true" />-->
<!--This is an optional configuration section where aspects of dotnetopenauth can be customized. For a complete set of configuration options see http://www.dotnetopenauth.net/developers/code-snippets/configuration-options/--> <openid>
<relyingParty>
<security requireSsl="false">
Uncomment the trustedProviders tag if your relying party should only accept positive assertions from a closed set of OpenID Providers.
<trustedProviders rejectAssertionsFromUntrustedProviders="true">
<add endpoint="https://www.google.com/accounts/o8/ud" />
</trustedProviders>
</security>
<behaviors>
<!--The following OPTIONAL behavior allows RPs to use SREG only, but be compatible
with OPs that use Attribute Exchange (in various formats).-->
<add type="DotNetOpenAuth.OpenId.RelyingParty.Behaviors.AXFetchAsSregTransform, DotNetOpenAuth.OpenId.RelyingParty" />
</behaviors>
</relyingParty></openid></dotNetOpenAuth><uri>
<!--The uri section is necessary to turn on .NET 3.5 support for IDN (international domain names),
which is necessary for OpenID urls with unicode characters in the domain/host name.
It is also required to put the Uri class into RFC 3986 escaping mode, which OpenID and OAuth require.-->
<idn enabled="All" />
<iriParsing enabled="true" />
</uri></configuration>
答案 0 :(得分：1)
请尝试从以下位置清除日志文件并重新启动sql server： -
C：\ Documents and Settings \您的pc-user \ Local Settings \ Application Data \ Microsoft \ Microsoft SQL Server Data \ SQLEXPRESS