VB.Net concatenating strings, adding strange spaces

Question

I'm sending a function a structure property that's a string (that's been already processed). It's an IP addr. Specifically:

 Dim ipaddr As String = "192.168.2.112"

At least, this is the value that we get after I do some processing. It looks like this in my local variable window mid build, so I know that it's looking ok. I'm trying to make a request string for the HTTP command. So I concatenate like so:

 Dim ReqStr As String = "http://" & ipaddr & "/cgi-bin/cmd/"

BUT doing so makes these strange spaces! As in the resulting string is

"http://192.168.2.112   /cgi-bin/cmd"

I thought the resulting code was maybe getting non ASCII character values, so I put it though a "\S+" regular expression, or I did ipaddr.trimend() or .trim, etc. ALL of these add the spaces. When I look at ipaddr in the locals when building, it ends at the proper end of the ipaddr value.

Yet, when I just put a hard coded string ("192.168.2.112") into the ipaddr's place in the string concatenation, no spaces. How do I get rid of the "secret" ascii characters I can't see?

Edit

Here is a sample of code which reproduces the problem:

Dim bytes() As Byte = {49, 57, 50, 46, 49, 54, 56, 46, 50, 46, 49, 49, 50, 0, 0, 0}
Dim ipaddr As String = Encoding.ASCII.GetString(bytes)
Dim ReqStr As String = "http://" & ipaddr.TrimEnd() & "/cgi-bin/cmd/"

The code above works as expected, no strange chars in the resulting string. If you get that result then something else is at work here — Steve
– Steve, Commented Mar 26, 2014 at 13:59
@Neel while it is a good site, it is hardly the reference for VB.NET — Steve
– Steve, Commented Mar 26, 2014 at 14:00
@neel - you should use MSDN as the official source. Have a look at this: msdn.microsoft.com/en-us/library/te2585xw.aspx — Matt Wilko
– Matt Wilko, Commented Mar 26, 2014 at 14:01
While debugging, please open your Immediate Window and type ?System.Text.Encoding.Unicode.GetBytes(ReqStr) and press enter. Then copy and paste the output of that command into your question. That will help us to reproduce and better understand your problem. — Steven Doggart
– Steven Doggart, Commented Mar 26, 2014 at 14:01

Matt Wilko · Accepted Answer · 2014-03-26 15:56:42Z

2

The byte array that you posted shows that you have NUL characters in your string so the standard Trim won't work as this only removes spaces.

Try using the overloaded Trim which accepts characters to Remove the null characters:

Dim ReqStr As String = "http://" & ipaddr.Trim(Convert.ToChar(0)) & "/cgi-bin/cmd/"

A better solution might be to use the IPAddress Type (from the System.Net namespace) to hold your IP address. This won't solve your problem but it will throw a runtime error converting your rogue array into an address:

Dim ip As IPAddress = Nothing
If Not IPAddress.TryParse(Encoding.ASCII.GetString(bytes), ip) Then
    'ip address is not valid
End If
Dim ReqStr As String = "http://" & ip.ToString & "/cgi-bin/cmd/"

edited Mar 26, 2014 at 15:56

answered Mar 26, 2014 at 14:14

Matt Wilko

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