Check for special characters (/*-+_@&$#%) in a string?

The easiest way it to use a regular expression:

Regular Expression for alphanumeric and underscores

Using regular expressions in .net:

http://www.regular-expressions.info/dotnet.html

MSDN Regular Expression

Regex.IsMatch

var regexItem = new Regex("^[a-zA-Z0-9 ]*$");

if(regexItem.IsMatch(YOUR_STRING)){..}

Try this way.

public static bool hasSpecialChar(string input)
    {
        string specialChar = @"\|!#$%&/()=?»«@£§€{}.-;'<>_,";
        foreach (var item in specialChar)
        {
            if (input.Contains(item)) return true;
        }

        return false;
    }

string s = @"$KUH% I*$)OFNlkfn$";
var withoutSpecial = new string(s.Where(c => Char.IsLetterOrDigit(c) 
                                            || Char.IsWhiteSpace(c)).ToArray());

if (s != withoutSpecial)
{
    Console.WriteLine("String contains special chars");
}

Simple:

function HasSpecialChars(string yourString)
{
    return yourString.Any( ch => ! Char.IsLetterOrDigit( ch ) )
}