Writing to the Event Log

In ASP.NET, error can be handled programmatically by writing appropriate code in the page-level error event, for errors on an individual page or in the application-level error event for handling errors that may occur in any page of the application.

Therefore, code for writing in the Event Log should be written in either of the events, depending on the requirement of the application. To illustrate this example, I have written the code in the application-level event with the error mode set to "RemoteOnly" and the defaultRedirect attribute to error.htm. The application-level error event should be included in the global file global.asax within the same application folder.

The contents of the global file can be given as follows:

Writing Log Entry in the Event Log

Imports System.Web
Imports System.Web.SessionState
Imports System.Diagnostics

Public Class Global
    Inherits System.Web.HttpApplication

     Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)

        Dim ErrorDescription As String = Server.GetLastError.ToString

        'Creation of event log if it does not exist  
        Dim EventLogName As String = "ErrorSample"
        If (Not EventLog.SourceExists(EventLogName)) Then
            EventLog.CreateEventSource(EventLogName, EventLogName)
        End If

        ' Inserting into event log
        Dim Log As New EventLog()
        Log.Source = EventLogName
        Log.WriteEntry(ErrorDescription, EventLogEntryType.Error)

    End Sub

End Class

Custom Error Pages and Sending Email to Admin

Imports System.Web
Imports System.Web.SessionState
Imports System.Web.Mail

Public Class Global
    Inherits System.Web.HttpApplication
 
    Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)

        Dim mail As New MailMessage()
        Dim ErrorMessage = "The error description is as follows : " &_
            Server.GetLastError.ToString
        mail.To = "administrator@domain.com"
        mail.Subject = "Error in the Site"
        mail.Priority = MailPriority.High
        mail.BodyFormat = MailFormat.Text
        mail.Body = ErrorMessage
        SmtpMail.Send(mail)

    End Sub

End Class

Deleting Record fron DataBase

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
-- =============================================
-- Author:
-- Create date: <28-06-2007>
-- Description:
-- =============================================
ALTER Procedure [dbo]. [spDeleteRows]
/*
Recursive row delete procedure.
It deletes all rows in the table specified that conform to the criteria selected,
while also deleting any child/grandchild records and so on. This is designed to do the
same sort of thing as Access's cascade delete function. It first reads the sysforeignkeys
table to find any child tables, then deletes the soon-to-be orphan records from them using
recursive calls to this procedure. Once all child records are gone, the rows are deleted
from the selected table. It is designed at this time to be run at the command line. It could
also be used in code, but the printed output will not be available.
*/
(
@cTableName varchar(250 ), /* name of the table where rows are to be deleted */
@cCriteria nvarchar(1000), /* criteria used to delete the rows required */
@iRowsAffected int OUTPUT /* number of records affected by the delete */
)
As
set nocount on
declare @cTab varchar(1000 ), /* name of the child table */
@cCol varchar (1000), /* name of the linking field on the child table */
@cRefTab varchar(1000), /* name of the parent table */
@cRefCol varchar(1000), /* name of the linking field in the parent table */
@cFKName varchar (1000), /* name of the foreign key */
@cSQL nvarchar(4000), /* query string passed to the sp_ExecuteSQL procedure */
@cChildCriteria nvarchar(4000), /* criteria to be used to delete
records from the child table */
@iChildRows int /* number of rows deleted from the child table */
/* declare the cursor containing the foreign key constraint information */
DECLARE cFKey CURSOR LOCAL FOR
SELECT SO1.name AS Tab,
SC1.name AS Col,
SO2.name AS RefTab,
SC2.name AS RefCol,
FO.name AS FKName
FROM dbo.sysforeignkeys FK
INNER JOIN dbo. syscolumns SC1 ON FK.fkeyid = SC1.id
AND FK .fkey = SC1.colid
INNER JOIN dbo.syscolumns SC2 ON FK.rkeyid = SC2 .id
AND FK.rkey = SC2.colid
INNER JOIN dbo.sysobjects SO1 ON FK .fkeyid = SO1. id
INNER JOIN dbo. sysobjects SO2 ON FK.rkeyid = SO2.id
INNER JOIN dbo.sysobjects FO ON FK.constid = FO .id
WHERE SO2.Name = @cTableName
OPEN cFKey
FETCH NEXT FROM cFKey INTO @cTab, @cCol, @cRefTab , @cRefCol, @cFKName
WHILE @@FETCH_STATUS = 0
BEGIN
/* build the criteria to delete rows from the child table. As it uses the
criteria passed to this procedure, it gets progressively larger with
recursive calls */
SET @cChildCriteria = @cCol + ' in (SELECT [' + @cRefCol + '] FROM [' +
@cRefTab + '] WHERE ' + @cCriteria + ')'
--print 'Deleting records from table ' + @cTab
/* call this procedure to delete the child rows */
EXEC spDeleteRows @cTab, @cChildCriteria , @iChildRows OUTPUT
FETCH NEXT FROM cFKey INTO @cTab, @cCol, @cRefTab , @cRefCol, @cFKName
END
Close cFKey
DeAllocate cFKey
/* finally delete the rows from this table and display the rows affected */
SET @cSQL = 'DELETE FROM [' + @cTableName + '] WHERE ' + @cCriteria
--print @cSQL
EXEC sp_ExecuteSQL @cSQL
print 'Deleted ' + CONVERT(varchar, @@ROWCOUNT) + ' records from table ' + @cTableName

Split Function In sql server

CREATE FUNCTION dbo.Split(@String nvarchar(4000), @Delimiter char(1))
RETURNS @Results TABLE (Items nvarchar(4000))
AS
BEGIN
DECLARE @INDEX INT
DECLARE @SLICE nvarchar(4000)
-- HAVE TO SET TO 1 SO IT DOESNT EQUAL Z
-- ERO FIRST TIME IN LOOP
SELECT @INDEX = 1
-- following line added 10/06/04 as null
-- values cause issues
IF @String IS NULL RETURN
WHILE @INDEX !=0
BEGIN
-- GET THE INDEX OF THE FIRST OCCURENCE OF THE SPLIT CHARACTER
SELECT @INDEX = CHARINDEX(@Delimiter,@STRING)
-- NOW PUSH EVERYTHING TO THE LEFT OF IT INTO THE SLICE VARIABLE
IF @INDEX !=0
SELECT @SLICE = LEFT(@STRING,@INDEX - 1)
ELSE
SELECT @SLICE = @STRING
-- PUT THE ITEM INTO THE RESULTS SET
INSERT INTO @Results(Items) VALUES(@SLICE)
-- CHOP THE ITEM REMOVED OFF THE MAIN STRING
SELECT @STRING = RIGHT(@STRING,LEN(@STRING) - @INDEX)
-- BREAK OUT IF WE ARE DONE
IF LEN(@STRING) = 0 BREAK
END
RETURN
END