Remove punctuation

In programs, strings often contain unneeded characters. In VB.NET there are many ways to remove punctuation characters from strings.

IsPunctuation

Here we use the Char.IsPunctuation function. It handles all punctuation characters. It is built into .NET and returns a Boolean telling us whether the char is punctuation.

Example

We introduce TrimPunctuation. This counts punctuation characters at the start and the end. We use 2 for-loops and call Char.IsPunctuation to check each character.

Module Module1

    Sub Main()
        Dim values() As String = {"One?", "--two--", "...three!",
                                  "four", "", "five*"}

        ' Loop over strings and call TrimPunctuation.
        For Each value As String In values
            Console.WriteLine(TrimPunctuation(value))
        Next

    End Sub

    Function TrimPunctuation(ByVal value As String)

        ' Count leading punctuation.
        Dim removeFromStart As Integer = 0
        For i As Integer = 0 To value.Length - 1 Step 1
            If Char.IsPunctuation(value(i)) Then
                removeFromStart += 1
            Else
                Exit For
            End If
        Next

        ' Count trailing punctuation.
        Dim removeFromEnd As Integer = 0
        For i As Integer = value.Length - 1 To 0 Step -1
            If Char.IsPunctuation(value(i)) Then
                removeFromEnd += 1
            Else
                Exit For
            End If
        Next

        ' Remove leading and trailing punctuation.
        Return value.Substring(removeFromStart,
                               value.Length - removeFromEnd - removeFromStart)

    End Function

End Module
One
two
three
four

five

Discussion

There are other ways to remove punctuation—Trim() can remove a set of characters. You can call Trim with an array of punctuation characters and it will work in the same way.

Performance note

An iterative method that tests characters individually is often the fastest one. Regex has overhead. The downside to using For-loops is that it involves more lines of code.

Summary

This function removes punctuation and is efficient. Some ways to remove punctuation are better than others—and testing for correctness is important.