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

Cast each char to an int, then compare its ascii code to the ascii table, which you can find all over the internet: http://www.asciitable.com/

    {
        char[] input = txtInput.Text.ToCharArray();
        StringBuilder sbResult = new StringBuilder();

        foreach (char c in input)
        {
            int asciiCode = (int)c;
            if (
                //Space
                asciiCode == 32
                ||
                // Period (.)
                asciiCode == 46
                ||
                // Percentage Sign (%)
                asciiCode == 37
                ||
                // Underscore
                asciiCode == 95
                ||
                ( //0-9, 
                    asciiCode >= 48
                    && asciiCode <= 57
                )
                ||
                ( //A-Z
                    asciiCode >= 65
                    && asciiCode <= 90
                )
                ||
                ( //a-z
                    asciiCode >= 97
                    && asciiCode <= 122
                )
            )
            {
                sbResult.Append(c);
            }
        }

        txtResult.Text = sbResult.ToString();
    }