Difference B/W IQueryable and IEnumerable

Question

What is the difference between IQueryable and IEnumerable?

Puneet Kankar · Answer

Hi Rehman, If you are use IEnumerable when querying data from in-memory collections like List, Array collection etc And when querying data from out-memory (like remote database, service) collections so you are use IQueryable. ... While querying data from database, IQueryable execute select query on server side with all filters. For better understanding check below links. check video link https://www.youtube.com/watch?v=yfPGFapabAY check link https://www.aspdotnet-suresh.com/2016/09/differences-between-iqueryable-and-ienumerable-in-csharp-with-example.html https://medium.com/@mohamedabdeen/iqueryable-vs-ienumerable-in-net-92a15a803da3

Mageshwaran R · Answer

Hi, Please refer the below link, it might helps you https://www.c-sharpcorner.com/UploadFile/a20beb/ienumerable-vs-iqueryable-in-linq/

Salman Beg · Answer

Hi. You can follow up with this link, https://www.c-sharpcorner.com/UploadFile/a20beb/ienumerable-vs-iqueryable-in-linq/

Rajanikant Hawaldar · Answer

Hi Rehaman, 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, yielding 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). https://docs.microsoft.com/en-us/previous-versions/dotnet/articles/bb394939(v=msdn.10)?redirectedfrom=MSDN