C#十六进制转ascii

Question

I'm trying to convert a String of hex to ASCII, using this:

public void ConvertHex(String hexString)
{
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < hexString.Length; i += 2)
    {
        String hs = hexString.Substring(i, i + 2);
        System.Convert.ToChar(System.Convert.ToUInt32(hexString.Substring(0, 2), 16)).ToString();
    }
    String ascii = sb.ToString();
    MessageBox.Show(ascii);
}

but I get an out or bounds exception, I'm sure its a glaring error but other code I have tried does not work either. What am I doing wrong?

Answer 1

This code will convert the hex string into ASCII, you can copy paste this into a class and use it without instancing

public static string ConvertHex(String hexString)
{
    try
    {
        string ascii = string.Empty;

        for (int i = 0; i < hexString.Length; i += 2)
        {
            String hs = string.Empty;

            hs   = hexString.Substring(i,2);
            uint decval =   System.Convert.ToUInt32(hs, 16);
            char character = System.Convert.ToChar(decval);
            ascii += character;

        }

        return ascii;
    }
    catch (Exception ex) { Console.WriteLine(ex.Message); }

    return string.Empty;
}

Notes

2 = the no. of hexString chars used to represent an ASCII character.

System.Convert.ToUInt32(hs, 16) = "convert the base 16 hex substrings to an unsigned 32 bit int"

Answer 2

There arefourthree problems here:

1. Since you're incrementing i by 2 on each iteration, you need to terminate at hexString.Length - 1 . This doesn't actually matter; incrementing by two after the final iteration will bring the counter above the checked length regardless.
2. You're taking the wrong number of characters from hexString .
3. hs is never used.
4. You're not appending anything to sb .

Try this:

for (int i = 0; i < hexString.Length; i += 2)
{
    string hs = hexString.Substring(i, 2);
    sb.Append(Convert.ToChar(Convert.ToUInt32(hs, 16)));
}

Note that there's no need to qualify the types with their namespace, System (assuming you've referenced it at the top of the file with a using statement).

Answer 3

String hs = hexString.Substring(i, i + 2);
System.Convert.ToChar(System.Convert.ToUInt32(hexString.Substring(0, 2), 16)).ToString();

Do you notice you're never using hs ??

And that you're converting the first 2 chars over and over?

Answer 4

Since you are incrementing your index by 2, you need to stop your loop one-before-the-end of the length of the string. Otherwise your last iteration of the loop will try to read characters past the end of the string.

for (int i = 0; i < hexString.Length - 1, i += 2)