IQueryable and IEnumerable

Question

can anyone please explain this in simple words IQueryable and IEnumerable

scropio gurl · Answer

Ehsan Sajjad and what var when we used this like var query = from table ....

Rajeesh Menoth · Answer

Hi IEnumerable IEnumerable exists in System.Collections Namespace. IEnumerable is best to query data from in-memory collections like List Array etc. While query data from database IEnumerable execute select query on server side load data in-memory on client side and then filter data. IEnumerable is suitable for LINQ to Object and LINQ to XML queries. IEnumerable supports deferred execution. IEnumerable doesn’t supports custom query. IEnumerable doesn’t support lazy loading. Hence not suitable for paging like scenarios. Extension methods supports by IEnumerable takes functional objects. IQueryable IQueryable exists in System.Linq Namespace. IQueryable is best to query data from out-memory (like remote database service) collections. While query data from database IQueryable execute select query on server side with all filters. IQueryable is suitable for LINQ to SQL queries. IQueryable supports deferred execution. IQueryable supports custom query using CreateQuery and Execute methods. IQueryable support lazy loading. Hence it is suitable for paging like scenarios. Extension methods supports by IQueryable takes expression objects means expression tree. Reference : http://www.dotnet-tricks.com/Tutorial/linq/I8SY160612-IEnumerable-VS-IQueryable.html

Ehsan Sajjad · Answer

The major difference between these two is that IEnumerable is in memory collection while IQueryable executes the query on the database server and then fetches records if you don't cast it to IEnumerbale you can futher apply more queries on that IQueryable for example filtering sorting grouping. For IEnumerable these all operation will be done in memory while IQueryable translates it to database query and then executes it on server.

scropio gurl · Answer

??????

scropio gurl · Answer

ok now concept is little bit clear now will you tell me why we var?

scropio gurl · Answer

i also check these links but this is complciated

Vinay Singh · Answer

Hi check the links this will give you clear idea https://blogs.msdn.microsoft.com/erickt/2006/10/23/iqueryablet-vs-ienumerablet/ http://blog.falafel.com/understanding-ienumerable-iqueryable-c/ http://www.codeproject.com/Articles/766541/IEnumerable-vs-IQueryable

scropio gurl · Answer

in this synatax IEnumerable people = GetEnumerablePeople(); Person person = people.Where(x => x.Age > 18).FirstOrDefault(); IQueryable people = GetQueryablePeople(); Person person = people.Where(x => x.Age > 18).FirstOrDefault(); x => x.Age > 18 this is same in both IEnumerable and IQueryable so why we this is different ( Func ) and ( Expression > ) and still not clear :(

Vinay Singh · Answer

Hi have a look of the link IEnumerable represents a forward-only cursor of T . .NET 3.5 added extension methods that included the LINQ standard query operators like Where and First  with any operators that require predicates or anonymous functions taking Func . IQueryable implements the same LINQ standard query operators but accepts Expression > for predicates and anonymous functions. Expression is a compiled expression tree a broken-up version of the method (half-compiled if you will) that can be parsed by the queryable's provider and used accordingly. For example: IEnumerable people = GetEnumerablePeople(); Person person = people.Where(x => x.Age > 18).FirstOrDefault(); IQueryable people = GetQueryablePeople(); Person person = people.Where(x => x.Age > 18).FirstOrDefault(); In the first block x => x.Age > 18 is an anonymous method ( Func ) which can be executed like any other method. Enumerable.Where will execute the method once for each person yield ing values for which the method returned true . In the second block x => x.Age > 18 is an expression tree ( Expression > ) which can be thought of as is the 'Age' property > 18. This allows things like LINQ-to-SQL to exist because they can parse the expression tree and convert it into equivalent SQL. And because the provider doesn't need to execute until the IQueryable is enumerated (it implements IEnumerable  after all) it can combine multiple query operators (in the above example Where and FirstOrDefault ) to make smarter choices on how to execute the entire query against the underlying data source (like using SELECT TOP 1 in SQL). See: The .NET Standard Query Operators For detail check the link http://www.dotnet-tricks.com/Tutorial/linq/I8SY160612-IEnumerable-VS-IQueryable.html http://www.codeproject.com/Articles/732425/IEnumerable-Vs-IQueryable

scropio gurl · Answer

please give examples and how we use ? when i create any linq query i start from var i.e var q=from a in tablename......... when we use these IQueryable and IEnumerable

Vinay Singh · Answer

Hi The main difference between both are IQueryable : 1. It is faster then IEnumerable. 2. In case of this when we apply where clause in linq on that case in sql query will generate with where clause and then query will execute IEnumerable 1. It is less faster then IQurable. 2. In case of this when we apply where clause in linq on that case in sql query first generate the select statement and then apply the where clause.

IQueryable<T> and IEnumerable<T>

IQueryable<T>