How to get first object out from List<Object> using Linq

Question

I have below code in c# 4.0.

//Dictionary object with Key as string and Value as List of Component type object Dictionary<String, List<Component>> dic = new Dictionary<String, List<Component>>();  //Here I am trying to do the loping for List<Component> foreach (List<Component> lstComp in dic.Values.ToList()) {     // Below I am trying to get first component from the lstComp object.     // Can we achieve same thing using LINQ?     // Which one will give more performance as well as good object handling?     Component depCountry = lstComp[0].ComponentValue("Dep"); } 

Answer 1

Try:

var firstElement = lstComp.First(); 

You can also use FirstOrDefault() just in case lstComp does not contain any items.

http://msdn.microsoft.com/en-gb/library/bb340482(v=vs.100).aspx

Edit:

To get the Component Value:

var firstElement = lstComp.First().ComponentValue("Dep"); 

This would assume there is an element in lstComp. An alternative and safer way would be...

var firstOrDefault = lstComp.FirstOrDefault(); if (firstOrDefault != null)  {     var firstComponentValue = firstOrDefault.ComponentValue("Dep"); } 

Answer 2

[0] or .First() will give you the same performance whatever happens.
But your Dictionary could contains IEnumerable<Component> instead of List<Component>, and then you cant use the [] operator. That is where the difference is huge.

So for your example, it doesn't really matters, but for this code, you have no choice to use First():

var dic = new Dictionary<String, IEnumerable<Component>>(); foreach (var components in dic.Values) {     // you can't use [0] because components is an IEnumerable<Component>     var firstComponent = components.First(); // be aware that it will throw an exception if components is empty.     var depCountry = firstComponent.ComponentValue("Dep"); }