Asp.net c matches the image format of the absolute address

Asp tutorial. net c match the image format of an absolute address
Regex reg = new regex ("img [^>] *? Src \ s * = \ s *(? :"(? <1> [^ "] *)" | & apos ;(? <1> [^ & apos;] *) & apos;) ", regexoptions. ignorecase );
/*
// You can match an absolute address image, such as src = "c:/img/test.gif"
// And relative address src = "img/test.gif"

I want to use an expression to match only the absolute address.
Only src = "c:/img/test.gif" is matched, but src = "img/test.gif" is not matched"
*/

// Match the absolute address
Regex reg = new regex (@ " ", Regexoptions. ignorecase );