entity framework: conditional filter

Question

Let\'s say I have Customers table and I want to filter it by the following:

• Country: All, US, UK, Canada
• Income: All, low, high, medium
• Age:A

Answer 1

You can include conditional parameter this way:

return Customers.Where(
                customer =>
                customer.Name == Name &&
                (Age == "All" || customer.Age == Age) &&
                (Income == "All" || customer.Income == Income) &&
                (Country == "All" || customer.Country == Country)
                ).ToList();

If some condition is true (e.g. country is equal to All), then all parameter condition becomes true, and this parameter does not filter result.

Answer 2

LINQ to Entity queries return IQueryable's, so you can build your query this way:

IQueryable<Person> query = context.People;

if (Country != "All")
{
    query = query.Where(p => p.Country == Country);
}

if (Income != "All")
{
    query = query.Where(p => p.Income == Income);
}

if (Age != "All")
{
    query = query.Where(p => p.Age == Age);
}

List<Person> fetchedPeople = query.ToList();

This case is almost too simple, but this is very helpful in more complex situations when you need to add filtering dynamically.