我在用index.aspx作开始页面的时候，之后运行，就出现如下错误：An error has occurred while establishing a connection to the server.&nbsp;&nbsp;When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)，这是怎么回事呢？？<br/><br/><br/>下面是WEB.config的部分代码 <br/>&lt;configuration&gt;<br/> &lt;configSections&gt;<br/>&nbsp;&nbsp;&lt;sectionGroup name=&quot;system.web.extensions&quot; type=&quot;System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot;&gt;<br/>&nbsp;&nbsp; &lt;sectionGroup name=&quot;scripting&quot; type=&quot;System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot;&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp;&lt;section name=&quot;scriptResourceHandler&quot; type=&quot;System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot; requirePermission=&quot;false&quot; allowDefinition=&quot;MachineToApplication&quot;/&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp;&lt;sectionGroup name=&quot;webServices&quot; type=&quot;System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot;&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp; &lt;section name=&quot;jsonSerialization&quot; type=&quot;System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot; requirePermission=&quot;false&quot; allowDefinition=&quot;Everywhere&quot;/&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp; &lt;section name=&quot;profileService&quot; type=&quot;System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot; requirePermission=&quot;false&quot; allowDefinition=&quot;MachineToApplication&quot;/&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp; &lt;section name=&quot;authenticationService&quot; type=&quot;System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot; requirePermission=&quot;false&quot; allowDefinition=&quot;MachineToApplication&quot;/&gt;<br/>&nbsp;&nbsp;&nbsp;&nbsp; &lt;section name=&quot;roleService&quot; type=&quot;System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35&quot; requirePermission=&quot;false&quot; allowDefinition=&quot;MachineToApplication&quot;/&gt;&lt;/sectionGroup&gt;&lt;/sectionGroup&gt;&lt;/sectionGroup&gt;&lt;/configSections&gt;&lt;appSettings&gt;<br/>&nbsp;&nbsp;&lt;add key=&quot;DbConnection&quot; value=&quot;Persist Security Info=False;Data Source=.;Initial Catalog=v_Graduation;User ID=sa;Password=sa;&quot;/&gt;