c# - Test if string is a guid without throwing exceptions? -

i want try convert string guid, don't want rely on catching exceptions (

• for performance reasons - exceptions expensive
• for usability reasons - debugger pops
• for design reasons - expected not exceptional

in other words code:

public static boolean trystrtoguid(string s, out guid value) {     try     {         value = new guid(s);         return true;     }     catch (formatexception)     {         value = guid.empty;         return false;     } } 

is not suitable.

i try using regex, since guid can parenthesis wrapped, brace wrapped, none wrapped, makes hard.

additionally, thought guid values invalid(?)

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update 1

christiank had idea catch formatexception, rather all. changed question's code sample include suggestion.

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update 2

why worry thrown exceptions? expecting invalid guids often?

the answer yes. why using trystrtoguid - am expecting bad data.

example 1 namespace extensions can specified appending guid folder name. might parsing folder names, checking see if text after final . guid.

c:\program files c:\program files.old c:\users c:\users.old c:\usermanager.{ce7f5aa5-6832-43fe-bae1-80d14cd8f666} c:\windows c:\windows.old 

example 2 might running heavily used web-server wants check validity of posted data. don't want invalid data tying resources 2-3 orders of magnitude higher needs be.

example 3 might parsing search expression entered user.

if enter guid's want process them specially (such searching object, or highlight , format specific search term in response text.)

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update 3 - performance benchmarks

test converting 10,000 guids, , 10,000 bad guids.

catch formatexception:    10,000 good:     63,668 ticks    10,000 bad:   6,435,609 ticks  regex pre-screen try-catch:    10,000 good:    637,633 ticks    10,000 bad:     717,894 ticks  com interop clsidfromstring    10,000 good:    126,120 ticks    10,000 bad:      23,134 ticks 

p.s. shouldn't have justify question.

performance benchmarks

catch exception:    10,000 good:    63,668 ticks    10,000 bad:  6,435,609 ticks  regex pre-screen:    10,000 good:   637,633 ticks    10,000 bad:    717,894 ticks  com interop clsidfromstring    10,000 good:   126,120 ticks    10,000 bad:     23,134 ticks 

com intertop (fastest) answer:

/// <summary> /// attempts convert string guid. /// </summary> /// <param name="s">the string try convert</param> /// <param name="value">upon return contain guid</param> /// <returns>returns true if successful, otherwise false</returns> public static boolean trystrtoguid(string s, out guid value) {    //clsidfromstring returns empty guid null strings       if ((s == null) || (s == ""))       {             value = guid.empty;             return false;       }     int hresult = pinvoke.objbase.clsidfromstring(s, out value);    if (hresult >= 0)    {       return true;    }    else    {       value = guid.empty;       return false;    } }   namespace pinvoke {     class objbase     {         /// <summary>         /// function converts string generated stringfromclsid function original class identifier.         /// </summary>         /// <param name="sz">string represents class identifier</param>         /// <param name="clsid">on return contain class identifier</param>         /// <returns>         /// positive or 0 if class identifier obtained         /// negative if call failed         /// </returns>         [dllimport("ole32.dll", charset = charset.unicode, exactspelling = true, preservesig = true)]         public static extern int clsidfromstring(string sz, out guid clsid);     } } 

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bottom line: if need check if string guid, , care performance, use com interop.

if need convert guid in string representation guid, use

new guid(somestring);