Dynamic Column Creation Problem with Telerik RadGrid

by demtron on Monday, February 02, 2009 10:04 AM

As part of a large eCommerce project, I needed to be able to extend a grid control into a custom control and dynamically add columns.  I needed to change the order of events that determined when and how columns would be added.  After a rather large modification of several hundred lines of code, I found that the grid would throw  errors such as "Cannot create column with the specified type name".  AJAX sorting, filtering, and refreshes threw this error every time after the initial grid display.  This vexed me for over two days until I found the Telerik forums post at http://www.telerik.com/community/forums/aspnet-ajax/grid/dynamic-creation-of-columns.aspx.  The solution was to set the EnableColumnsViewState property of the MasterTableView to false and create the columns on Page.Init or on each Page.Load.

Sometimes, the easiest changes fix the most hair-pulling problems.  :-)


VB.Net Converting Number to Words

by demtron on Monday, February 02, 2009 09:30 AM

I found some example code on the Microsoft site at http://support.microsoft.com/kb/213360 that shows how to convert a decimal number to words using VBA.  This type of code is specially useful for tranforming currency amounts into words for printing on a check.  I needed to have this code converted to VB.Net, so here it is:


'Main Function
Function SpellNumber(ByVal MyNumber As String) As String
Dim Dollars As String = ""
Dim Cents As String = ""
Dim Temp As String = ""
Dim DecimalPlace, Count As Integer
Dim Place(9) As String
Place(2) = " Thousand "
Place(3) = " Million "
Place(4) = " Billion "
Place(5) = " Trillion "
' String representation of amount.
MyNumber = Trim(Str(MyNumber))
' Position of decimal place 0 if none.
DecimalPlace = InStr(MyNumber, ".")
' Convert cents and set MyNumber to dollar amount.
If DecimalPlace > 0 Then
Cents = GetTens(Left(Mid(MyNumber, DecimalPlace + 1) & _
"00", 2))
MyNumber = Trim(Left(MyNumber, DecimalPlace - 1))
End If
Count = 1
Do While MyNumber <> ""
Temp = GetHundreds(Right(MyNumber, 3))
If Temp <> "" Then Dollars = Temp & Place(Count) & Dollars
If Len(MyNumber) > 3 Then
MyNumber = Left(MyNumber, Len(MyNumber) - 3)
Else
MyNumber = ""
End If
Count = Count + 1
Loop
Select Case Dollars
Case ""
Dollars = "No Dollars"
Case "One"
Dollars = "One Dollar"
Case Else
Dollars = Dollars & " Dollars"
End Select
Select Case Cents
Case ""
Cents = " and No Cents"
Case "One"
Cents = " and One Cent"
Case Else
Cents = " and " & Cents & " Cents"
End Select
SpellNumber = Dollars & Cents
End Function
' Converts a number from 100-999 into text 
Function GetHundreds(ByVal MyNumber As String) As String
Dim Result As String
If Val(MyNumber) = 0 Then : Return "" : Exit Function : End If
MyNumber = Right("000" & MyNumber, 3)
' Convert the hundreds place.
If Mid(MyNumber, 1, 1) <> "0" Then
Result = GetDigit(Mid(MyNumber, 1, 1)) & " Hundred "
End If
' Convert the tens and ones place.
If Mid(MyNumber, 2, 1) <> "0" Then
Result = Result & GetTens(Mid(MyNumber, 2))
Else
Result = Result & GetDigit(Mid(MyNumber, 3))
End If
GetHundreds = Result
End Function
' Converts a number from 10 to 99 into text. 
Function GetTens(ByVal TensText As String) As String
Dim Result As String
Result = ""           ' Null out the temporary function value.
If Val(Left(TensText, 1)) = 1 Then   ' If value between 10-19...
Select Case Val(TensText)
Case 10 : Result = "Ten"
Case 11 : Result = "Eleven"
Case 12 : Result = "Twelve"
Case 13 : Result = "Thirteen"
Case 14 : Result = "Fourteen"
Case 15 : Result = "Fifteen"
Case 16 : Result = "Sixteen"
Case 17 : Result = "Seventeen"
Case 18 : Result = "Eighteen"
Case 19 : Result = "Nineteen"
Case Else
End Select
Else                                 ' If value between 20-99...
Select Case Val(Left(TensText, 1))
Case 2 : Result = "Twenty "
Case 3 : Result = "Thirty "
Case 4 : Result = "Forty "
Case 5 : Result = "Fifty "
Case 6 : Result = "Sixty "
Case 7 : Result = "Seventy "
Case 8 : Result = "Eighty "
Case 9 : Result = "Ninety "
Case Else
End Select
Result = Result & GetDigit _
(Right(TensText, 1))  ' Retrieve ones place.
End If
GetTens = Result
End Function
' Converts a number from 1 to 9 into text. 
Function GetDigit(ByVal Digit As String) As String
Select Case Val(Digit)
Case 1 : GetDigit = "One"
Case 2 : GetDigit = "Two"
Case 3 : GetDigit = "Three"
Case 4 : GetDigit = "Four"
Case 5 : GetDigit = "Five"
Case 6 : GetDigit = "Six"
Case 7 : GetDigit = "Seven"
Case 8 : GetDigit = "Eight"
Case 9 : GetDigit = "Nine"
Case Else : GetDigit = ""
End Select
End Function


Reading User Agents to Identify Bot Traffic

by demtron on Monday, February 02, 2009 08:41 AM

Sometimes, it's a real pain to tell the difference between a human visitor and a bot when reviewing a Web server traffic log.  I recently had an acquiantance ask me for information on this topic.  I found a great resource at http://www.botsvsbrowsers.com/category/1/index.html that catalogs nearly 3000 known user agents that are associated with bots.

In many cases, there are identifiers such as GoogleBot, msnbot and Slurp that are easy to spot as these are common bot user agent signatures.  Unfortunately, there's no common identifier among all of them.  I figure that this list could be pulled into a lookup table and used for matching against a server log.  What I wan't able to identify is how frequently this list is updated for new signatures.


Thread aborted using Response.Redirect in ASP.Net

by demtron on Monday, February 02, 2009 08:13 AM

I added a Response.Redirect to a .Net Web page and began receiving a "Thread was being aborted" error on a line of code that executed Response.Redirect.  Without really considering it, this error made sense based on the place where I added the code.

Response.Redirect will call Response.End by design.  However, this will also raise a ThreadAbortException.  In my case, it was because the redirect line was within a try...catch block.  I found two ways to handle this:

  1. Change Response.Redirect(<URL>) to Response.Redirect(<URL>, false)
  2. Move the line to outside the try...catch block
I ended up using method #2, but both options worked for me.

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