Standard Query Operators

The LINQ standard query operators can be applied to any .NET array or collection that implements the IEnumerable or IEnumerable<T> interfaces


These operators are method that provide querying capabilities.
There are two sets of query operators:
IEnumerable<T>
IQueryable<T>


These extension methods can be called by using either static method syntax or instance method syntax


Aggregate 
All 
Any 
AsEnumerableConverting
Average 
Cast 
Concat 
Contains 
Count 
DefaultIfEmpty 
Distinct 
ElementAt 
ElementAtOrDefault 
Empty 
Except 
First 
FirstOrDefault 
GroupBy 
GroupJoin 
Intersect 
Join 
Last 
LastOrDefault 
LogCount 
LongCount 
Max 
Min 
OfTypeConverting
OrderBy 
OrderByDescending 
Range 
Repeat 
Reverse 
Select 
SelectMany 
SequenceEqual 
Single 
SingleOrDefault 
Skip 
SkipWhile 
Sum 
Take 
TakeWhile 
ThenBy 
ThenByDescending 
ToArray 
ToDictionary 
ToList 
ToLookup 
Union 
Where 


LINQ to Objects


This refers to the use of LINQ queries with any IEnumerable or IEnumerable<T> collection directly.
You can also use LINQ to query any enumerable collections such as List<T>, Array or Dictionary<TKey, TValue>


These queries look similar to SQL queries but they are very different
LINQ brings an element of functional programming into C#
It adds various new keywords for building query expressions
The LINQ query expressions are translated into a chain of extension method calls or standard query operators.


System.Linq 
var linq_query = from x in myobjects
                      where x.Name = "Simon"
                      orderby x.Age
                      select new { Name = x.Name, Age = x.Age }




foreach (var item in linq_query) 
{
   Console.Writeline("{0}. {1}, item.Name, item.Age);
}


Provide a list of standard LINQ query operators
Where - filters the data
OrderBy - sorts the dataset
Select - specific columns in dataset


Where

subset = myobjects.Where(o => o.Value == false) 



OrderBy

subset = myobjects.OrderBy(o => o.Length) 



Select

subset = myobjects.Select(o => new {o.Name, o.Value}; 




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