使用者程式碼未處理 System.Data.SqlClient.SqlException
報以下錯誤，因小弟才開始接觸.net，所以還請各位能幫忙分析下
謝謝！！
----------------------------------報錯部分------------------------------
使用者程式碼未處理 System.Data.SqlClient.SqlException
HResult=-2146232060
Message=建立連接至 SQL Server 時，發生網路相關或執行個體特定的錯誤。找不到或無法存取伺服器。確認執行個名稱是否正確，以及 SQL Server 是否設定為允許遠端連線。 (provider: Named Pipes Provider, error: 40 - 無法開啟至 SQL Server 的連接)
Source=.Net SqlClient Data Provider
ErrorCode=-2146232060
Class=20
LineNumber=0
Number=53
Server=""
State=0
StackTrace:
於 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
於 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
於 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFailover)
於 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
於 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
於 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
於 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions)
於 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
於 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
於 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnectionOptions userOptions)
於 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnectionOptions userOptions)
於 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
於 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
於 System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
於 System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
於 System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
於 System.Data.SqlClient.SqlConnection.Open()
於 ConferenceRoomsBook.Common.TCsLocalSrv.GetDataTable(String SQL, String[] ParamNames, Object[] ParamValues) 於 E:\ConferenceRoomsBook\Common\TCsLocalSrv.cs: 行 78
於 ConferenceRoomsBook.Common.TCsEmpInfo.GetEmpInfoByName(String empUserName) 於 E:\ConferenceRoomsBook\Common\TCsEmpInfo.cs: 行 31
於 ConferenceRoomsBook._Default.DoInit() 於 E:\ConferenceRoomsBook\Default.aspx.cs: 行 25
於 ConferenceRoomsBook._Default.Page_Load(Object sender, EventArgs e) 於 E:\ConferenceRoomsBook\Default.aspx.cs: 行 17
於 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
於 System.Web.UI.Control.OnLoad(EventArgs e)
於 System.Web.UI.Control.LoadRecursive()
於 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException: System.ComponentModel.Win32Exception
HResult=-2147467259
Message=找不到網路路徑。
ErrorCode=-2147467259
NativeErrorCode=53
InnerException: 問題;
[解决办法]
检查sql server是否启用tcp/ip协议，防火墙设置，你的连接字符串中的主机和sql server实例名是否正确。
