Resolved return all letters left of number in string

[Fedaykin]

I'm trying to return only the first letters before the first number in as string. I tried several iterations of Regex and gave up on that.

I want to do something like:

Dim source as String = "CP1,CP3-CP5,CP8"
Dim rc As String = Left(source, "[0-9]"))

[\CODE]

In this instance I just want to return "CP".

 

[Solitaire]

Test each character with Char.IsLetter

 Dim str, newstr As String, ch As Char, N As Integer
        newstr = ""
        str = "CP1,CP3-CP5,CP8"
        N = str.Length
        For x As Integer = 0 To N - 1
            ch = str.Chars(x)
            If Char.IsLetter(ch) Then
                newstr &= ch
            Else
                Exit For
            End If
        Next
        MessageBox.Show(newstr)

 

[Fedaykin]

Works perfectly, thank you!

I really thought there was a simple one-liner for this particular function, but your solution works great.

 

[jmcilhinney]

I really thought there was a simple one-liner for this particular function

There is:

Dim substr = New String(str.TakeWhile(Function (ch) Not Char.IsDigit(ch)).ToArray())

Any time you use a loop, there's most likely a way to collapse the code using a LINQ query. It's not always the best idea, because it can make the code hard to read. Not so much in this case though, I think.

 

[Fedaykin]

Yes, in my search for this solution I read a few times about LINQ in place of loops. I'm going to pop this one in there too to see how it works. Thank you.

 

[jmcilhinney]

There is:

Dim substr = New String(str.TakeWhile(Function (ch) Not Char.IsDigit(ch)).ToArray())

Any time you use a loop, there's most likely a way to collapse the code using a LINQ query. It's not always the best idea, because it can make the code hard to read. Not so much in this case though, I think.

Note that that code will get all characters before the first digit. If you want all the leading letters then you should use this:

Dim substr = New String(str.TakeWhile(Function (ch) Char.IsLetter(ch)).ToArray())

The result will be the same for your example data but, if you had something that was neither a letter nor a digit in between then the results would differ.