For Each...Next Help VB.NET

Lets analyse what is happening here:

For Each num As Char In rtb 

Since rtb is a String, and String implements IEnumerable<Char>, the above is essentially you saying - for each character in the string - which is not what you want.

You need to first split the string into groups that each represents a number - for example:

Dim numbers As String() = rtb.Split(" ") 

Then, you could iterate over the list and convert each of the strings (these are still strings) to a actual number, which you will need to convert to a character:

For Each num As String In numbers ' num can be "82", for instance Next num 

Do something like this:

Dim rtb As String = Nothing rtb = "82 40 30" For Each num As var In rtb.Split(" "C) Next 

Of course if you would like to split numbers using other char just replace " "C with what you need

You’re not iterating over numbers, you’re iterating over individual characters. You didn’t tell us how the numbers are separated in the input but for the sake of discussion let’s assume that you are using spaces. We can use String.Split to get individual numbers from the stream:

Dim rtb As String = "82 23 47 123" Dim Ascii = System.Text.Encoding.ASCII For each numToken As String In rtb.Split(" "c) Dim num As Byte If Not Byte.TryParse(numToken, num) ' Signal error Exit For End If Dim buffer As Char() = Ascii.GetChars(New Byte() { num }) Dim result As Char = buffer(0) ' Do something with `result` Next 

One important bit: I’ve used the System.Text.Encoding class to do the mapping between ASCII codes and characters. This may seem unnecessarily complex but do want to do this. Encodings unfortunately are complex and it’s counter-productive to pretend otherwise and use homegrown ad-hoc conversions. In particular, using Chr is not appropriate since that doesn’t actually handle ASCII, it handles Unicode code points (with some restrictions) which are similar, but not the same. Using Chr in the above code would be misleading and thus a surefire way to introduce bugs further down the road. It’s important to document your assumptions, and if your assumption is that the input consists of ASCII, then the conversion code should reflect that.

Use three digits for each character. Most lower-case letters are three digits anyway.