private string GetPrefixFromQName(string value) {
int colonOffset;
int len = ValidateNames.ParseQName(value, 0, out colonOffset);
if (len == 0 || len != value.Length) {
return null;
}
if (colonOffset != 0) {
return value.Substring(0, colonOffset);
}
else {
return string.Empty;
}
}
}