What is the use of XML comments in C#

Question

What is the use of XML comments in C# than signal line and multiple line comments.

i.Single line
Eg:
//This is a Single line comment

ii. Multiple line (/* */)
Eg:
 /*This is a multiple line comment
We are in line 2
Last line of comment*/

iii. XML Comments (///).
Eg:
/// summary;
///  Set error message for multilingual language.
/// summary

Answer 1

From XML Documentation Comments (C# Programming Guide):

When you compile with the /doc option, the compiler will search for all XML tags in the source code and create an XML documentation file.

Also XML comments used by Visual Studio for IntelliSense:

/// <summary>
///  This class performs an important function.
/// </summary>
public class MyClass{}

Will give you nice hints when you are typing code or hovering cursor over member which has xml comments:

NOTE: Usually you should add xml comments only to publicly visible types or members. If member is internal or private, then it's good, but not necessary. There is nice tool GhostDoc (available as extension to Visual Studio) which can generate XML comments from type or member name. It's nice to check if you have good naming - if generated comment is not clear, then you should improve name of member.

I also suggest use simple (non-xml) comments as little, as possible. Because comment is a form of code duplication - it duplicates information which you already have in your code. And here is two problems:

• Your code is not clear enough and you should improve it (renaming, extracting classes or members) instead of adding comments
• When code changes, comments often stay unchanged (programmers are lazy). So when time passes comments become obsolete and confusing.

Good comments should describe why you writing code instead of duplicating what code is doing.