C# Remove special characters

Question

I want to remove all special characters from a string. Allowed characters are A-Z (uppercase or lowercase), numbers (0-9), underscore (_), white space ( ), pecentage(%) or the d

Answer 1

You can simplify the first method to

StringBuilder sb = new StringBuilder();
foreach (char c in input)
{
    if (Char.IsLetterOrDigit(c) || c == '.' || c == '_' || c == ' ' || c == '%')
    { sb.Append(c); }
}
return sb.ToString();

which seems to pass simple tests. You can shorten it using LINQ

return new string(
    input.Where(
        c => Char.IsLetterOrDigit(c) || 
            c == '.' || c == '_' || c == ' ' || c == '%')
    .ToArray());