Method 'System.Object DynamicInvoke(System.Object[])' has no supported translation to SQL

Question

Let's say that I have a table named Poll and I want to write a LINQ Extension to list all polls that have ID belong to an array. For e.g:

void Main()
{
    long[] ids = new long[]{ 1,2,3,4,5,6,7,8,9 };

    ListFail<Poll>(Poll, p => p.ID, ids); //Failed!
    ListOK<Poll>(Poll, p => p.ID, ids); //OK!
}

public void ListFail<T>(Table<T> obj, Func<T, long> idProperty, long[] ids) where T : class
{
    obj.Where(p => ids.Contains(idProperty(p))).ToList().Dump();
}

public void ListOK<T>(Table<T> obj, Func<T, long> idProperty, long[] ids) where T : class
{
    obj.ToList().Where(p => ids.Contains(idProperty(p))).ToList().Dump();
}

I don't know why I get the error on ListFail

Method 'System.Object DynamicInvoke(System.Object[])' has no supported translation to SQL.

and when I added the ToList() before Where then it run well on ListOK but of course I don't want to get the whole Poll table.

Any idea?

Answer 1

Change Func<T, long> to Expression<Func<T, long>>. Right now, because of this, EF doesn't understand it.