Why does ReSharper suggest I convert a for loop into a LINQ expression?

Question

In Visual Studio Re-Sharper keeps recommending I convert a for loop to a linq expression but what is the reason for this?

Which is faster?

Here are some example loops where resharper suggests a linq conversion:

foreach (XmlNode legendEntryNode in _legendEntryNodes) {     var xmlElement = legendEntryNode["FeatureType"];      if (xmlElement == null || !xmlElement.InnerText.Equals(featuretype)) continue;      var xmlNodeList = legendEntryNode.SelectNodes("Themes/Theme");      if (xmlNodeList != null)      foreach (XmlNode themeNode in xmlNodeList)     {         var element = themeNode["Value"];          if (element == null || !element.InnerText.Equals(v)) continue;          var xmlElement1 = themeNode["Icon"];          if (xmlElement1 != null)         {             string iconname = "<ms:ICON>" + xmlElement1.InnerText + "</ms:ICON>";              var element1 = themeNode["Highlight"];              if (element1 != null)             {                 string highlightname = "<ms:HIGHLIGHT>" + element1.InnerText + "</ms:HIGHLIGHT>";                 gml = gml.Insert(c, iconname + highlightname);                  c += (iconname.Length + highlightname.Length);             }         }         break;     } } 

And this simpler example:

for (int i = 0; i < getPointsRequest.Attribs.Length; i++) {     string attribName = getPointsRequest.Attribs[i].AttributeName;      if (!String.IsNullOrEmpty(attribName))     {         sqlQuery += "<ms:" + attribName + ">||\"" + attribName + "\"||</ms:" + attribName + ">";     } } 

Answer 1

Speed is very often irrelevant in large portions of your code - you should write code the simplest way, and then measure it to make sure it's fast enough.

If your for loop is really just querying, then LINQ is absolutely a great way to end up with more readable code. It's not universally applicable, but it's something you should at least bear in mind frequently.

Quite often a for loop can be converted into a query to be evaluated lazily, and then a foreach loop which performs some action on each value returned by the query. That can help separate the two aspects, letting you focus on one at a time when reading the code. It's important to keep LINQ queries as queries though, rather than using side-effects within them - it's designed to have a functional approach, which really doesn't mix pleasantly with side-effects.

If you have some concrete examples, we could give more opinions about which loops would make sense to convert to use LINQ, and which wouldn't.

Answer 2

No performance gain as such, but some benefits

• Makes code more readable.
• Reduces the number of lines.
• Easy to maintain.
• In some cases you don't require temporary variables, which you might require in for loop. Using Linq you can chain queries.

For more details you can refer:

• LINQ query operators: lose that foreach already
• The “Anti-For” Campaign
• Life After Loops

Hope this helps you.