Better way to detect XML?

Question

Currently, I have the following c# code to extract a value out of text. If its XML, I want the value within it - otherwise, if its not XML, it can just return the text itself.

String data = "..." try {     return XElement.Parse(data).Value; } catch (System.Xml.XmlException) {     return data; } 

I know exceptions are expensive in C#, so I was wondering if there was a better way to determine if the text I'm dealing with is xml or not?

I thought of regex testing, but I dont' see that as a cheaper alternative. Note, I'm asking for a less expensive method of doing this.

Answer 1

You could do a preliminary check for a < since all XML has to start with one and the bulk of all non-XML will not start with one.

(Free-hand written.)

// Has to have length to be XML if (!string.IsNullOrEmpty(data)) {     // If it starts with a < after trimming then it probably is XML     // Need to do an empty check again in case the string is all white space.     var trimmedData = data.TrimStart();     if (string.IsNullOrEmpty(trimmedData))     {        return data;     }      if (trimmedData[0] == '<')     {         try         {             return XElement.Parse(data).Value;         }         catch (System.Xml.XmlException)         {             return data;         }     } } else {     return data; } 

I originally had the use of a regex but Trim()[0] is identical to what that regex would do.