IEnumerable & IQueryable

Question

hi What is IEnumerable & IQueryable type object in Linq ? Please Explain it.

MuthuMari M · Answer

Hi pls refer this url http://stackoverflow.com/questions/252785/what-is-the-difference-between-iqueryablet-and-ienumerablet/252857#252857 thanks. If this post is useful then mark it as  Accepted Answer

Shenishetty Sravani · Answer

To return a collection we use IQueryable.But it differs in many ways from other return types. Using IQueryable  you can save a lot of resources. It is used for filtering the records in extension methods. When we use: public static IQueryable GetEmployeeDetails() { return Employees.Where(e => e.Salary >= 10000); } When the method is executedthe SQL executed will be Select * from Employee where Salary>=10000. It returns only those records in to the collection which satisfy the condition. but when we use IEnumerable the SQL executed will be Select * from Employee and returns every record. IQueryable extends IEnumerable and also stores the Expressions (not just Funcs). Whereas a Func is a delegate and an Expression is well an expression that is able to be traversed at runtime. And that means it can be translated into SQL. The .Where extension method for an IEnumerable takes a Func whereas the .Where extension method for an IQueryable takes an Expression >. What this means is that if we change our filter extension method to take an IEnumerable it will be using the IEnumerable's .Where extension method passing in a compiled delegate instead of a traversable expression (they both can be inferred from the same code in the above case e => e.Salary >= 10000 how it gets compiled depends on which method you call). For more information on Linq follow the link below: new link

Vulpes · Answer

LINQ supports two types of query - local queries for local object collections and interpreted queries for remote data sources. Local queries operate over collections which implement IEnumerable and use the query operators in the Enumerable static class. These emit normal IL at compile time. Interpreted queries operate over collections which implement IQueryable and use the query operators in the Queryable static class. These emit 'expression trees' that are interpreted at runtime - hence the name. It is also possible to query non-generic collections which implement IEnumerable (for local queries) or IQueryable (for interpreted queries) by casting to a specific type.