Var vs iEnumerable

1. Difference between Var and IEnumerable
S.No Var IEnumerable
1 When to use ? When to use ?
Use Var type when we want to Use IEnumerable when we already
make a "custom" type on the know the type of query result.
fly.
2 Good for: Good for:
Var is also good for remote IEnumerable is good for in-memory
collection. collection.
IEnumerable Example
MyDataContext dc = new MyDataContext ();
IEnumerable<Employee> list = dc.Employees.Where(p => p.Name.StartsWith("S"));
list = list.Take<Employee>(10);
Generated SQL statements of above query will be :
SELECT
[t0].[EmpID], [t0].[EmpName], [t0].[Salary] FROM [Employee] AS [t0]
WHERE [t0].[EmpName] LIKE @p0
Notice that in this query "top 10" is missing since IEnumerable filters records on client
side
Var Example
MyDataContext dc = new MyDataContext ();
var list = dc.Employees.Where(p => p.Name.StartsWith("S"));
list = list.Take<Employee>(10);
Generated SQL statements of above query will be :
SELECT TOP 10
[t0].[EmpID], [t0].[EmpName], [t0].[Salary] FROM [Employee] AS [t0]
WHERE [t0].[EmpName] LIKE @p0
Notice that in this query "top 10" is exist since var is a IQueryable type that executes
query in SQL server with all filters.
IEnumerable Type
IEnumerable is a forward only collection and is useful when we already know the type of
query result. In below query the result will be a list of employee that can be mapped (type
cast) to employee table.
IEnumerable<tblEmployee> lst =(from e in tblEmployee
where e.City=="Delhi"
select e);

2. Reference:
http://www.dotnet-tricks.com/Tutorial/linq/aPNK140912-Var-VS-IEnumerable.html
And, further updates on difference between questions and answers, please visit my
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