For example, if I had a Linq to SQL data context, or if I had ADO.NET Entity Framework entities that mapped to a database table, and I want to select a single Customer...
What is the difference between:
MyDatabaseContext.Customers.Any(c => c.CustomerId == 3)
and
MyDatabaseContext.Customers.Where(c => c.CustomerId == 3)
Are both even valid?
.Any<> - return type bool
.Where<> - return type IQueryable
EDIT: Corrected question wording after accepting answer from Fredrik Mörk - thanks.
Check the documentation again:
Any<> returns a bool indicating whether at least one item meets the criteriaWhere<> returns an IEnumerable containing the items that meet the criteriaThere may be a performance difference in that Any stops as soon as it can determine the result (when it finds a matching item), while Where will need to always loop over all items before returning the result. So if you only need to check whether there are any matching items, Any will be the method for the job.
Any() returns a bool. I.e. are there any elements matching the condition. Use Any() if you just want to know if you have elements to work with. E.g. prefer Any() over Count() == 0 for instance as the latter will possible enumerate the entire sequence to find out if it is empty or not.
Where() returns a sequence of the elements matching the condition.
Any returns a bool while Where returns an IQueryable. Being lazy, one would expect Any to terminate as soon as one satisfying element is found (returning true) while Where will search them all.
If you want to select a single customer, Single is what you are looking for.
Any<> checks whether any items satisfy the criterion, i.e. returns bool, meaning that it only has to find the first item, which can be very fast. Whereas Where<> enumerates all the items that satisfy the condition, meaning that it has to iterate the whole collection.
Any tests the lambda/predicate and returns true/false
Where returns the set of objects for which lambda/predicate holds true as IQueryable