How to validate that a string doesn't contain HTML using C#

Question

Does anyone have a simple, efficient way of checking that a string doesn't contain HTML? Basically, I want to check that certain fields only contain plain text. I thought about looking for the < character, but that can easily be used in plain text. Another way might be to create a new System.Xml.Linq.XElement using:

XElement.Parse("<wrapper>" + MyString + "</wrapper>") 

and check that the XElement contains no child elements, but this seems a little heavyweight for what I need.

Answer 1

The following will match any matching set of tags. i.e. <b>this</b>

Regex tagRegex = new Regex(@"<\s*([^ >]+)[^>]*>.*?<\s*/\s*\1\s*>"); 

The following will match any single tag. i.e. <b> (it doesn't have to be closed).

Regex tagRegex = new Regex(@"<[^>]+>"); 

You can then use it like so

bool hasTags = tagRegex.IsMatch(myString);