Check if string contains non-ASCII

Question

Hello

To check if inside a string, there are any non-ASCII characters, is this code snippet ok?

Encoding.UTF8.GetByteCount(inString) <> inString.Length = True/False
False: full ANSI string
True: string contains Non-ANSI characters

Not sure what are possible exceptions, and is it the safe way to do such check?

Thanks :)

Answer 1

The code snippet you provided checks if a string contains non-ASCII characters by comparing the byte count of the UTF-8 encoding with the string length. While this approach can work, there are a few things to consider and potential issues:

1. Character Encoding: UTF-8 encoding can represent characters with more than one byte, so Encoding.UTF8.GetByteCount counts all bytes (including those for characters that require more than one byte). If the string contains characters that require multiple bytes (such as accented characters, emojis, or other non-ASCII characters), the byte count will differ from the length of the string.
2. Comparison Logic: The logic you're using compares Encoding.UTF8.GetByteCount(inString) with inString.Length. The result of this comparison gives True when there are non-ASCII characters because UTF-8 characters that require more than 1 byte will cause the byte count to exceed the string length.
3. Potential Exceptions: In general, the GetByteCount method won't throw exceptions unless the string is null. If inString is null, it will throw an ArgumentNullException.

To safely check if a string contains non-ASCII characters and handle potential exceptions, consider this approach:

Dim containsNonASCII As Boolean = False

Try
    containsNonASCII = Encoding.UTF8.GetByteCount(inString) <> inString.Length
Catch ex As ArgumentNullException
    ' Handle the case where inString is null
    containsNonASCII = False
End Try

If containsNonASCII Then
    ' String contains non-ASCII characters
Else
    ' String is ASCII (ANSI) only
End If

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hth

Marcin