Asp.net application suddenly stopped responding to requests - vb.net

Question

Good day, I am a newbie in .net programming and also IIS web deployment configuration.
Currently, I have an asp.net application that runs using Framework 4.5 on IIS. For the first month of having the application deployed on the server, it was running fine and smoothly. However, recently the application had issues whereby the login page would actually load but when the users key in their credentials, the page loading timer would show and it disappears, leaving the user stranded, unable to login.
In addition, the server had undergone security procedures as stated below:
Windows Hardening (Using Windows Server 2012)
SQL Server Hardening (SQL Server 2012) and port was changed to 8001
Also, the architecture of the application is that:
The Application is deployed in AMLWEB server
The SQL Server Database is in AMLDB server
So, the connection actually goes across server and the login authentication is actually authenticated against Active Directory.
The screenshot as attached:
Unhandled exception screenshot
When checked on the event viewer, the below warning was seen that may suggest to be contributing to the issue:
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 1/18/2015 5:27:15 PM
Event time (UTC): 1/18/2015 9:27:15 AM
Event ID: 2ac169fff7284e86b7b0844e5d9ccab1
Event sequence: 4
Event occurrence: 1
Event detail code: 0
Application information:
Application domain: /LM/W3SVC/1/ROOT/AML-1-130660468323976167
Trust level: Full
Application Virtual Path: /AML
Application Path: D:\AML\
Machine name: AMLWEB
Process information:
Process ID: 6756
Process name: w3wp.exe
Account name: IIS APPPOOL\.NET v4.5
Exception information:
Exception type: InvalidOperationException
Exception message: The ConnectionString property has not been initialized.
at System.Data.SqlClient.SqlConnection.PermissionDemand()
at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at DBManager.DBManager.OpenConnection(String DBStrConn, Int16 DBType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\DBManager\DBManager.vb:line 50
at DBManager.DBManager.ExecuteSQLQuery_ReturnDS(String& ReturnErrorMsg, String SqlString, String DBConnString, Int16 DBType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\DBManager\DBManager.vb:line 190
at SQLAdminQueryManager.AdminQueryManager.AdminQueryManager_Staff_Login.Staff_Login_Retreive(cor_staff AppEntity, String DbSQLConnString, String DbType, String& ReturnErrorMsg, Object& ReturnObjDataset, String AccessType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\SQLAdminQueryManager\AdminQueryManager.vb:line 65
at Login_page_LDAP_Code.LoginButton_Click(Object sender, EventArgs e)
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
Request information:
Request URL: https://amlweb/AML/Login_page.aspx
Request path: /AML/Login_page.aspx
User host address: 10.1.67.61
User:
Is authenticated: False
Authentication Type:
Thread account name: IIS APPPOOL\.NET v4.5
Thread information:
Thread ID: 10
Thread account name: IIS APPPOOL\.NET v4.5
Is impersonating: False
Stack trace: at System.Data.SqlClient.SqlConnection.PermissionDemand()
at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at DBManager.DBManager.OpenConnection(String DBStrConn, Int16 DBType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\DBManager\DBManager.vb:line 50
at DBManager.DBManager.ExecuteSQLQuery_ReturnDS(String& ReturnErrorMsg, String SqlString, String DBConnString, Int16 DBType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\DBManager\DBManager.vb:line 190
at SQLAdminQueryManager.AdminQueryManager.AdminQueryManager_Staff_Login.Staff_Login_Retreive(cor_staff AppEntity, String DbSQLConnString, String DbType, String& ReturnErrorMsg, Object& ReturnObjDataset, String AccessType) in C:\Users\TESS-HP003\Desktop\AML\ES_Library\SQLAdminQueryManager\AdminQueryManager.vb:line 65
at Login_page_LDAP_Code.LoginButton_Click(Object sender, EventArgs e)
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
Custom event details:
However, the connection string was indeed had been set up properly as below:
Web.config
<connectionStrings>
<add name="AMLDBConnectionString" connectionString="Data Source=AMLDB01, 8001;Initial Catalog=AML_DB;integrated security=true; uid=sa; pwd=p#ssw0rd"/>
</connectionStrings>
And it was set up as a global variable as so:
GlobalSQLConnString = ConfigurationManager.ConnectionStrings("AMLDBConnectionString").ToString
GlobalDBType As Int16 = 1
The line which actually executed to connect to the DB:
blnReturnValue = objSqlQuery.Staff_Login_Retreive(objBE, GlobalSQLConnString, GlobalDBType, strErrorMsgReturn, returnDS, "S")
The method invoked:
Public Function Staff_Login_Retreive(ByVal AppEntity As BusinessEntities.cor_staff, _
ByVal DbSQLConnString As String, ByVal DbType As String, _
ByRef ReturnErrorMsg As String, ByRef ReturnObjDataset As Object, _
Optional ByVal AccessType As String = "S") As Boolean
With AppEntity
SQlQuery = "SELECT * "
SQlQuery += " FROM cor_staff "
SQlQuery += " WHERE cor_staff.cor_userid =N'" & AppEntity.cor_userid & "'"
End With
'
If AccessType.ToUpper = "R" Then
ReturnObjDataset = ExecuteSQLQuery_ReturnIDR(ReturnErrorMsg, SQlQuery, DbSQLConnString, DbType)
Else
ReturnObjDataset = ExecuteSQLQuery_ReturnDS(ReturnErrorMsg, SQlQuery, DbSQLConnString, DbType)
End If
'
If ReturnErrorMsg.Trim.Length = 0 Then
Return True
Else
Return False
End If
'
End Function
Edited
Since the above code would actually run through and would actually be invoked on this line:
ReturnObjDataset = ExecuteSQLQuery_ReturnDS(ReturnErrorMsg, SQlQuery, DbSQLConnString, DbType)
The connection would only be opened here:
Public Function ExecuteSQLQuery_ReturnDS(ByRef ReturnErrorMsg As String, ByVal SqlString As String, ByVal DBConnString As String, ByVal DBType As Int16) As DataSet
ReturnErrorMsg = ""
Dim DS As New DataSet
'
If DBType = 1 Then
Try
OpenConnection(DBConnString, DBType)
Dim sqlCmd As New SqlCommand(SqlString, sqlConn)
sqlCmd.CommandTimeout = 0
Dim sqlDaAdp As New SqlDataAdapter(sqlCmd)
sqlDaAdp.Fill(DS)
sqlCmd = Nothing
sqlDaAdp = Nothing
CloseConnection(DBType)
Return DS
Catch ex As SqlException
If ex.Number = 18456 Or ex.Number = 4060 Then
ReturnErrorMsg = "Database Connection Error >> Error No : " & ex.Number
Else
ReturnErrorMsg = "SQL Statement Error >> Error No : " & ex.Number
End If
CloseConnection(DBType)
Return Nothing
End Try
ElseIf DBType = 3 Then
Try
OpenConnection(DBConnString, DBType)
Dim oledbCmd As New OleDbCommand(SqlString, oleDbconn)
Dim oledbDaAdp As New OleDbDataAdapter(oledbCmd)
oledbDaAdp.Fill(DS)
oledbDaAdp = Nothing
oledbDaAdp = Nothing
CloseConnection(DBType)
Return DS
Catch ex As OleDbException
If ex.ErrorCode = -2147217887 Then
ReturnErrorMsg = "Database Connection Error >> Error Code : " & ex.ErrorCode
Else
ReturnErrorMsg = "SQL Statement Error >> Error Code : " & ex.ErrorCode
End If
CloseConnection(DBType)
Return Nothing
End Try
End If
'
Return Nothing
'
End Function
Open connection method:
Public Sub OpenConnection(ByVal DBStrConn As String, ByVal DBType As Int16)
Try
If DBType = 1 Then
sqlConn = New SqlConnection(DBStrConn)
If sqlConn.State = ConnectionState.Closed Then
sqlConn.Open()
Else
sqlConn.Close()
sqlConn.Open()
End If
ElseIf DBType = 3 Then
oleDbconn = New OleDbConnection(DBStrConn)
If oleDbconn.State = ConnectionState.Closed Then
oleDbconn.Open()
Else
oleDbconn.Close()
oleDbconn.Open()
End If
End If
'
Catch ex As Exception
Throw
End Try
End Sub
End of edited part
Does anyone have any idea why does such exception would occur?
So far, I've done the following to actually try to debug this issue:
Restart IIS
Restart Application Pool
Recycle Application Pool (every 12 hours, 8 a.m. and 8 p.m. specifically)
Restart SQL Server Service
None of the above worked. But when I actually tried accessing the application from a specific floor in which is the Security Team floor, the application actually starts functioning as usual, and others could actually access the application as well.
Please help, I'm totally going out of my mind about this issue.
Does it have anything to do with my deployment method, iis configuration or programming, I'm willing to listen to suggestions.
Thanks for your time.