Question

Wondering if it’s possible to create a dynamic linq query using linq to objects.

I have a screen where a user can filter on multiple things.
I Need to build an in memory filtering NOT using a database

So lets suppose I have a list of customers in memory and I would like to filter based on some multiselection.

I thought a method that I could pass a predicate would do the trick ,but obviously not.

How can I do it?

eg

public class Biz
{
    public List<Customer> GetAllByName(string name)
    {
        return Repository.Find(x=> x.Name == name);
    }
}

public class Repository
{
    private List<Customer> internalCustomerList = GetAllCustomers();

    public IEnumerable<Customer> Find(Expression<Func<T, bool>> predicate)
    {
        //How do I make below work in linq to object
        return  internalCustomerList.Where(predicate);//error here
    }
}

Answer 1

You can do:

public class Biz
{
    public List<Customer> GetAllByName(string name)
    {
        return Repository.Find(x=>x.Name == name);
    }
}

public class Repository
{
    private List<Customer> internalCustomerList = GetAllCustomers();

    public static IEnumerable<Customer> Find(Func<T, bool> predicate)
    {
        return internalCustomerList.Where(predicate);
    }
}

Please note that List<T> does not have an overload for Expression<Func<T, bool>>. Only IQueryable<T> has. See more at http://msdn.microsoft.com/en-us/library/bb882637.aspx