How to parse hex values into a uint?

Question

uint color; 
bool parsedhex = uint.TryParse(TextBox1.Text, out color); 
//where Text is of the form 0xFF0000
if(parsedhex)
   //...

doesn't work. What am i doing wrong?

Nescio · Accepted Answer · 2008-09-19T01:20:31.113

138

Try

Convert.ToUInt32(hex, 16)  //Using ToUInt32 not ToUInt64, as per OP comment

edited Sep 19 '08 at 01:20

answered Sep 19 '08 at 01:14

Nescio

27,645
10
53
72

5

Something to keep in mind (although it may not apply to this particular integer conversion)... if the input is bad, Convert.ToUInt32 could be orders of magnitude slower than UInt32.TryParse, like Convert.ToDouble vs Double.TryParse: http://stackoverflow.com/questions/586436/double-tryparse-or-double-convert-what-is-faster-and-more-safe/586539#586539 Also, it's not always clear what it's converting: http://stackoverflow.com/questions/586436/double-tryparse-or-double-convert-what-is-faster-and-more-safe/586460#586460 – Triynko Oct 26 '11 at 16:43
1

As @Triynko said, this is a faulty process, as it is liable to throw exceptions. uint.TryParse would be preferable, since it returns a Boolean value indicating success or failure, rather than throwing an exception. – Zenexer Oct 27 '12 at 16:57
1

This approach with `Convert.ToUInt32` will handle the '0x' prefix as part of the input. – Derek W Sep 22 '15 at 17:05

score 54 · Answer 2 · edited May 22 '21 at 18:10

54

You can use an overloaded TryParse() which adds a NumberStyle parameter to the TryParse call which provides parsing of Hexadecimal values. Use NumberStyles.HexNumber which allows you to pass the string as a hex number.

Note: The problem with NumberStyles.HexNumber is that it doesn't support parsing values with a prefix (ie. 0x, &H, or #), so you have to strip it off before trying to parse the value.

Basically you'd do this:

uint color;
var hex = TextBox1.Text;

if (hex.StartsWith("0x", StringComparison.CurrentCultureIgnoreCase) ||
    hex.StartsWith("&H", StringComparison.CurrentCultureIgnoreCase)) 
{
    hex = hex.Substring(2);
}

bool parsedSuccessfully = uint.TryParse(hex, 
        NumberStyles.HexNumber, 
        CultureInfo.CurrentCulture, 
        out color);

See the documentation for TryParse(String, NumberStyles, IFormatProvider, Int32) for an example of how to use the NumberStyles enumeration.

edited May 22 '21 at 18:10

Peter Duniho

68,759
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answered Sep 19 '08 at 01:19

Jeremy Wiebe

3,894
22
31

22

Personally, I'd call this behavior a bug. Why on earth would they call the flag **Allow**HexSpecifier if it doesn't actually allow any hex specifier? – Tom Lint Oct 08 '14 at 08:21
Keep in mind that there are at least two common hex specifiers out there: 0x and &H – Haymo Kutschbach Apr 06 '16 at 13:24
just found another potential representation: '#0000103A3C..' – Haymo Kutschbach Jun 15 '16 at 16:54

score 16 · Answer 3 · answered Sep 19 '08 at 01:18

16

Or like

string hexNum = "0xFFFF";
string hexNumWithoutPrefix = hexNum.Substring(2);

uint i;
bool success = uint.TryParse(hexNumWithoutPrefix, System.Globalization.NumberStyles.HexNumber, null, out i);

answered Sep 19 '08 at 01:18

Corey Ross

1,995
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16

score 6 · Answer 4 · answered Oct 10 '13 at 17:06

Here is a try-parse style function:

    private static bool TryParseHex(string hex, out UInt32 result)
    {
        result = 0;

        if (hex == null)
        {
            return false;
        }

        try
        {
            result = Convert.ToUInt32(hex, 16);

            return true;
        }
        catch (Exception exception)
        {
            return false;
        }
    }

How to parse hex values into a uint?

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