string toBeSearched = "code : ";
string code = myString.Substring(myString.IndexOf(toBeSearched) + toBeSearched.Length);
Something like this?
Perhaps you should handle the case of missing code :
…
string toBeSearched = "code : ";
int ix = myString.IndexOf(toBeSearched);
if (ix != -1)
{
string code = myString.Substring(ix + toBeSearched.Length);
// do something here
}