Does using a lambda expression passed into a method slow down an Entity Framework query?

Question

I have a method:

public static void GetObjects()
{
    using(MyContext context = new MyContext())
    {
         var objects = context.Bars.Where(b => b.Prop1         


        

Answer 1

The reason it is running slower is because you are passing in a Func which forces the context to retrive ALL Bars and then run the Func on the returned result set. A way to make this run better is to pass in Expression>

Putting that all together will result in the following:

public static void GetObjectsV2(Expression> whereFunc, Expression> selectPropFunc)
{
    using(MyContext context = new MyContext())
    {
         var objects = context.Bars.Where(whereFunc)
                       .Select(selectPropFunc)
                       .ToList();
         foreach(var object in objects)
         {
             // do something with the object
         }
    }
}