Basic Query Operations

Obtaing DataSource
From clause is used to include

• Data source 
• Range Variable : which store each element of data source.
• Syntax:  from <rangevariable> in <datasource objcet>

Selection 
Select clause is used to specify type of result  sequence returned after execution of query
Syntax:
select <rangevariable>;
select new { rangevariable1, rangevariable2,..}


Filtering 

• Only those element for which the expression is true is returned by the query.
• Any C# logical and relation operators can be used to specify expression. 
• Syntax: where <condition1 on range variable>  [<logical operator>] <condition2 on rangevariable>

Ordering

• orderby clause cause the data to be returned in sorted order (ascending or descending)
• Default order is ascending.
• Syntax: orderby  rangevariable  [[ascending | descending], ..]

Executing

• foreach loop is used to iterate through each element of range variable returned by LINQ query.
• Syntax: foreach (datatype  loopvariable  in  linqqryvariable)  {  ….    }

Grouping

• Groupby clause is used to group your results based on a key specified by the user
• Grouping refers to the operation of putting data into groups so that the elements in each group share a common attribute. 
• Syntax: group <range variable> by <grouping criteria>

Let clause

• Let clause creates a new range variable and store the result of sub expression.
• Once initialized range variable cannot store another value
• Syntax: let <new range variable> = [LINQ expression | other expression]

Set Operations

Based on the presence or absence of equivalent elements within the same or separate collections. The operations are

• Distinct: Remove duplicate values from the collections
• Except: Elements in first input sequence that are not in second input sequence.
• Intersect: Elements that are common to both input sequence.
• Union: Unique elements from both sequence.