显示错误“ConnectionString属性尚未初始化”

Question

我在vb.net和sql server中拥有一个拥有大量用户的网站。问题是，有时在白天，网站会抛出异常而不会显示网页的某些部分。使用会话和cookie执行身份验证。会话ID写在数据库表中，签出后将被删除。我不知道会发生什么，但是当我重新启动IIS时，问题就被消除了，但过了一段时间它又出现了。我的日志文件的堆栈跟踪如下。有什么问题？

UserID:rezagmc3       
SessionID:uup5l0koj3eacxl3pcqdxmbz
Form Data: No Form Data Found1: Error Description:The ConnectionString property has not been initialized.
1: Source:System.Data
1: Stack Trace:   at System.Data.SqlClient.SqlConnection.PermissionDemand()
1:    at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
1:    at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
1:    at System.Data.SqlClient.SqlConnection.Open()
1:    at SoratHesab.SqlHelperParameterCache.DiscoverSpParameterSet(SqlConnection connection, String spName, Boolean includeReturnValueParameter, Object[] parameterValues)
1:    at SoratHesab.SqlHelperParameterCache.GetSpParameterSetInternal(SqlConnection connection, String spName, Boolean includeReturnValueParameter)
1:    at SoratHesab.SqlHelperParameterCache.GetSpParameterSet(SqlConnection connection, String spName, Boolean includeReturnValueParameter)
1:    at SoratHesab.SqlHelperParameterCache.GetSpParameterSet(SqlConnection connection, String spName)
1:    at SoratHesab.mySqlHelperParameterCache.GetSpParameterSet(String SectionName, String spName)
1:    at SoratHesab.clsCAccOp.GetLastUpdatedDate(String SectionName)
1:    at SoratHesab.CAcc.Page_Load(Object sender, EventArgs e)
1: Target Site:Void PermissionDemand()