When to use AsEnumerable() along with EF to fetch data

Question

please see the below code

private IEnumerable<AutoCompleteData> GetAutoCompleteData(string searchTerm)
{
using (var context = new AdventureWorksEntities())
{
var results = context.Products
.Include("ProductSubcategory")
.Where(p => p.Name.Contains(searchTerm)
&& p.DiscontinuedDate == null)
.AsEnumerable()
.Select(p => new AutoCompleteData
{
Id = p.ProductID,
Text = BuildAutoCompleteText(p)
})
.ToArray();
return results;
}
}

please tell me why someone use .AsEnumerable() before select?

i use EF to fetch data but i never use .AsEnumerable() before select but some one used. it means there must be some reason to use there .AsEnumerable().

please discuss the significance of using .AsEnumerable() before select there?

if we remove .AsEnumerable() from EF query then does it execute and return data ?

here is my example for fetching data where i have not used AsEnumerable()

var customer = (from s in db.Customers
// select s;
select new CustomerDTO
{
CustomerID = s.CustomerID,
CompanyName = s.CompanyName,
ContactName = s.ContactName,
ContactTitle = s.ContactTitle,
Address = s.Address
});

thanks

Tridip Bhattacharjee · Answer

@Ramesh tell me when EF will fetch data as per my query above ? when .ToArray(); will be executed then it will fetch data from db? if yes then i can write the same query like this way....then what will be the harm? using (var context = new AdventureWorksEntities()) { var results = context.Products .Include("ProductSubcategory") .Where(p => p.Name.Contains(searchTerm) && p.DiscontinuedDate == null) .Select(p => new AutoCompleteData { Id = p.ProductID, Text = BuildAutoCompleteText(p) }) .ToArray(); return results; just drop .AsEnumerable() from above query. now tell me if possible what would be the difference between two query one with .AsEnumerable() and other without .AsEnumerable()

Ramesh Palanivel · Answer

Hi Tridip, AsEnumerable will not return result set imidiately, it formatting query like, if you are applying filter like where, take, skip , everything will applied first then finally the query will be executed. Tolist imidiately will execute your query

Mangesh G · Answer

Whenever we want to iterate on data or more specifically u want to loop on the data at that time use AsEnumerable