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Remove Letters from String to convert into integer

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Join Date: Sep 2007

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Remove Letters from String to convert into integer

Oct 11th, 2007

Hello, I need to remove letters and characters from a request.querystring in order to convert it into an integer. This is only extra precaution from people screwing around in the address bar directly. I have enough protection in place to protect errors. Let's say that I want to retrieve a current location that is kept by an integer from the querystring.

http.//www.mydomain.com/direction.aspx?loc=2

This works great, but then if someone does this:

http.//www.mydomain.com/direction.aspx?loc=2sdf;DROP

or something like it, it just automatically redirects to loc=1. I was hoping that someone could help me figure out how to request.querystring("loc") then pull out the invalid characters to keep it a string. Thinking off the top of my head, this is all I can think of which is FAR too lengthy. I know there is a shorter way:

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
Function MakeInteger()
Dim i As Integer
Dim loc As String = request.QueryString("loc")
 
Do While Not IsNumeric(loc)
  loc = Replace(loc, "a", "")
  loc = Replace(loc, "b", "")
  ...
  ...
loop
Return (loc)
End Function
Function MakeInteger()
Dim i As Integer
Dim loc As String = request.QueryString("loc")

Do While Not IsNumeric(loc)
  loc = Replace(loc, "a", "")
  loc = Replace(loc, "b", "")
  ...
  ...
loop
Return (loc)
End Function

Is there a way to do something like: loc = Replace(loc, [A-z], "") ?

I found this in C# I believe. Maybe someone who knows how to validly convert it to VB? Thanks

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
StringBuilder sb = new StringBuilder ();
for (int i=0; i< string.Length; i++)
if (char.IsLetterOrDigit(string[i])
sb.Append(string[i]);
StringBuilder sb = new StringBuilder ();
for (int i=0; i< string.Length; i++)
if (char.IsLetterOrDigit(string[i])
sb.Append(string[i]);

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Join Date: Oct 2007

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Re: Remove Letters from String to convert into integer

Oct 11th, 2007

h well i can only tell u as much as to use split functions , u can serch net for details , they split string into array of strings as needed, use the needed array member , more i can telll if u explain the problem in detail

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Re: Remove Letters from String to convert into integer

Oct 11th, 2007

I looked up the (char.IsLetterOrDigit) function. It seems like it would be best for me and I will probably do that later. I am pulling information from a database via integers found on the querystring. But I want extra protection that doesn't require redundant code. I know I can pull the information from the querystring and do a replace function for every character in the aplhabet, but that is 26 lines of code executed repeatedly whereas I should be able to search all A-z letters and remove them with a couple lines of code. I guess this is something I can do:

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
Function Public ConvertInt(ByVal stringtoint As String) As Integer
Dim i As Integer
'for this case, stringtoint will be equal to request.querystring("id") or something similiar
 
Do While Not IsNumeric(stringtoint)
  for i=0 to Len(stringtoint)
    If (char.IsLetterOrDigit(i)) = False then
      stringtoint = Replace(stringtoint, (char.IsLetterOrDigit(i)), "")
    End if
  next
loop
Return (stringtoint)
End Function
 
Function Public ConvertInt(ByVal stringtoint As String) As Integer
Dim i As Integer
'for this case, stringtoint will be equal to request.querystring("id") or something similiar

Do While Not IsNumeric(stringtoint)
  for i=0 to Len(stringtoint)
    If (char.IsLetterOrDigit(i)) = False then
      stringtoint = Replace(stringtoint, (char.IsLetterOrDigit(i)), "")
    End if
  next
loop
Return (stringtoint)
End Function

understand what I am after? I need to retrieve the querystring from the url. The querystring must be integer to proceed so I need to remove all letters and special chars.

Last edited by SheSaidImaPregy; Oct 11th, 2007 at 1:37 pm.

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Join Date: Oct 2007

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Re: Remove Letters from String to convert into integer

Oct 12th, 2007

yep dear , i got what u said , u want numerics and only numerics in querystring , and u are protecting against directly jotted querystring values in url..... thats right
well i have been taught to use query string in the least secure pages, well there are no of options like viewstate, session or application , u can use global vars too, but still if u r bent upon using query string than i might find out something about it, u'll have to do something like picking up each char and check for int. and ignore the whole if anything else... like that na
wel,, m from india , where r u from

---------------------------------------------------------------------------------------------------

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Originally Posted by SheSaidImaPregy

I looked up the (char.IsLetterOrDigit) function. It seems like it would be best for me and I will probably do that later. I am pulling information from a database via integers found on the querystring. But I want extra protection that doesn't require redundant code. I know I can pull the information from the querystring and do a replace function for every character in the aplhabet, but that is 26 lines of code executed repeatedly whereas I should be able to search all A-z letters and remove them with a couple lines of code. I guess this is something I can do:
Help with Code Tags

ASP.NET Syntax (Toggle Plain Text)
Function Public ConvertInt(ByVal stringtoint As String) As Integer
Dim i As Integer
'for this case, stringtoint will be equal to request.querystring("id") or something similiar
 
Do While Not IsNumeric(stringtoint)
  for i=0 to Len(stringtoint)
    If (char.IsLetterOrDigit(i)) = False then
      stringtoint = Replace(stringtoint, (char.IsLetterOrDigit(i)), "")
    End if
  next
loop
Return (stringtoint)
End Function
 
Function Public ConvertInt(ByVal stringtoint As String) As Integer Dim i As Integer 'for this case, stringtoint will be equal to request.querystring("id") or something similiar Do While Not IsNumeric(stringtoint) for i=0 to Len(stringtoint) If (char.IsLetterOrDigit(i)) = False then stringtoint = Replace(stringtoint, (char.IsLetterOrDigit(i)), "") End if next loop Return (stringtoint) End Function
understand what I am after? I need to retrieve the querystring from the url. The querystring must be integer to proceed so I need to remove all letters and special chars.

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Re: Remove Letters from String to convert into integer

Oct 12th, 2007

I'm from the US. Yeah, I have been working on a function that checks whether or not EACH digit in the string is a digit or not. The problem I am receiving from this is that if the querystring says "3serd", it says that there are invalid characters in the string. Can't seem to work around that. It's a unrequired extra protection and to keep functionality the best it can be. The only reason you should use querystrings is if you want the page to be bookmarked and that the information pulled is in no way required for any vital information via database. Like, if you have your url at mydomain.com/tutorial.aspx?id=209882, you can save it as a bookmark. But if you send your id's via textboxes or sessions, if someone bookmarks your page and comes back to it later, it will fail. As the only thing they see and your server see's is: mydomain.com/tutorial.aspx And I am sure you have some kind of coding that if there is no id specified, you redirect to another page which allows the user to pick or specify an id. You know what I mean? It's for bookmarking and favorites the use of querystrings. I also use UserID's in querystrings but only for the user's view as there requires serverside and session variables for that. I get picked on here and there for that, but I like seeing userid's, always have!

Anyway, this is what I have so far for my function above that fails if there are anything besides digits:

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
'Public Function MakeInt(ByVal stringint As String) As String
'Dim i As Integer
'
'if Len(stringint) > 0 then
'	Do While Not IsNumeric(stringint)
'		for i=0 to Len(stringint)
'			if (Char.IsDigit(stringint, (i))) = False then
'				stringint = Replace(stringint, (Mid(stringint, (i), 1)), "")
'			end if
'		next
'	loop
'	Return (stringint)
'end if
'End Function
'Public Function MakeInt(ByVal stringint As String) As String
'Dim i As Integer
'
'if Len(stringint) > 0 then
'	Do While Not IsNumeric(stringint)
'		for i=0 to Len(stringint)
'			if (Char.IsDigit(stringint, (i))) = False then
'				stringint = Replace(stringint, (Mid(stringint, (i), 1)), "")
'			end if
'		next
'	loop
'	Return (stringint)
'end if
'End Function

I am also working on this one below but haven't tested it yet. It should work..

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
'Public Function MakeInt(ByVal stringint As String) As String
'Dim lngCount As Long
'Dim strOut As String
'if not isnull(stringint) then
'	for lngCount = 1 to len(stringint)
'		if isnumeric(mid$(stringint, lngCount, 1)) then
'			strOut = strOut & mid$(stringint, lngCount, 1)
'		end if
'	next lngCount
'end if
'MakeInt = strOut
'end function
'Public Function MakeInt(ByVal stringint As String) As String
'Dim lngCount As Long
'Dim strOut As String
'if not isnull(stringint) then
'	for lngCount = 1 to len(stringint)
'		if isnumeric(mid$(stringint, lngCount, 1)) then
'			strOut = strOut & mid$(stringint, lngCount, 1)
'		end if
'	next lngCount
'end if
'MakeInt = strOut
'end function

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Re: Remove Letters from String to convert into integer

Oct 12th, 2007

Solved it. This works. Drops everything besides the digits.

 Help with Code Tags 
 ASP.NET Syntax (Toggle Plain Text) 
Public Function MakeInt(ByVal stringint As String) As String
Dim lngCount As Long
Dim strOut As String
if Len(stringint) > 0 then
  for lngCount = 1 to len(stringint)
    if isnumeric(mid$(stringint, lngCount, 1)) then
      strOut = strOut & mid$(stringint, lngCount, 1)
    end if
  next lngCount
end if
MakeInt = strOut
End Function
Public Function MakeInt(ByVal stringint As String) As String
Dim lngCount As Long
Dim strOut As String
if Len(stringint) > 0 then
  for lngCount = 1 to len(stringint)
    if isnumeric(mid$(stringint, lngCount, 1)) then
      strOut = strOut & mid$(stringint, lngCount, 1)
    end if
  next lngCount
end if
MakeInt = strOut
End Function

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Join Date: Oct 2007

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sauru_garg sauru_garg is offline

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Re: Remove Letters from String to convert into integer

Oct 13th, 2007

well thats good, now i understood , why u wanted to do querystrings ...
keep in touch

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Originally Posted by SheSaidImaPregy

Solved it. This works. Drops everything besides the digits.
Help with Code Tags

ASP.NET Syntax (Toggle Plain Text)
Public Function MakeInt(ByVal stringint As String) As String
Dim lngCount As Long
Dim strOut As String
if Len(stringint) > 0 then
  for lngCount = 1 to len(stringint)
    if isnumeric(mid$(stringint, lngCount, 1)) then
      strOut = strOut & mid$(stringint, lngCount, 1)
    end if
  next lngCount
end if
MakeInt = strOut
End Function
Public Function MakeInt(ByVal stringint As String) As String Dim lngCount As Long Dim strOut As String if Len(stringint) > 0 then for lngCount = 1 to len(stringint) if isnumeric(mid$(stringint, lngCount, 1)) then strOut = strOut & mid$(stringint, lngCount, 1) end if next lngCount end if MakeInt = strOut End Function