Server Error in '/' Application.

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Exception: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[Exception: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)]
   DTcms.DBUtility.DbHelperSQL.Query(String SQLString) +302
   DTcms.DAL.channel_site.GetList(Int32 Top, String strWhere, String filedOrder) +407
   DTcms.BLL.channel_site.GetModelList() +48
   DTcms.Web.UI.SiteDomains..ctor() +190
   DTcms.Web.UI.SiteDomains.GetSiteDomains() +253
   DTcms.Web.UI.HttpModule.GetCurrDomainPath(String requestDomain) +14
   DTcms.Web.UI.HttpModule.GetSitePath(String webPath, String requestPath, String requestDomain) +28
   DTcms.Web.UI.HttpModule.ReUrl_BeginRequest(Object sender, EventArgs e) +305
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +266


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1