When we working with Linq queries it’s important to know that  query doesn’t get executed when we define it. Rather it’s get executed we actually use it or enumerated it.

Possible Multiple Enumeration

//Avoid Reevaluating of Linq Queries
Console.WriteLine("First Enumeration");
var nums = new List<int> {1,2,3,4};
var result = from n in nums select new {Number=n,ExecutionTime=DateTime.Now.ToString("mm:ss:fff")};
foreach (var item in result)
{
Console.WriteLine(item);
}
foreach (var item in result)
{
Console.WriteLine(item);
}
Console.WriteLine(“Second Enumeration”);

Avoid Multiple enumeration Of IEnumerable

Console.WriteLine(“Second Enumeration”);
//You can avoid the multiple enumeration possible by converting the results to List,Dictionary,Array..
var goodresult = (from n in nums select new { Number = n, ExecutionTime = DateTime.Now.ToString("mm:ss:fff") }).ToList();
foreach (var item in goodresult)
{
Console.WriteLine(item);
}
foreach (var item in goodresult)
{
Console.WriteLine(item);
}
Enjoy..Coding…