Rewriting a LINQ Expression query to enable caching SQL Execution Plan

Question

While reading an article on Entity Framework performance, I came across this piece of information:

Secondly, the problem [SQL Server won’t reu

Answer 1

Let me recap.

You are building Expression> like this

var item = Expression.Parameter(typeof(T), "item");
var left = Expression.Property(item, idPropertyName);
Expression right = ...;
var body = Expression.Equal(left, right);
var predicate = Expression.Lambda>(body, item);

and the question is what should be used for right in order to make EF not treating it as a constant.

Apparently primitive value like

var right = Expression.Convert(Expression.Constant(convertedId), left.Type);

doesn't work, so the solution is to provide a property of some class instance. You solved it by using anonymous type, but of course there are many other ways to do that.

For instance, using a closure (like it would have been if you were not creating the expression manually)

Expression> closure = () => convertedId;
var right = Expresion.Convert(closure.Body, left.Type);

or Tuple instance (a bit verbose, but eliminates Expression.Convert)

var tuple = Activator.CreateInstance(
    typeof(Tuple<>).MakeGenericType(left.Type), convertedId);
var right = Expression.Property(Expression.Constant(tuple), "Item1");

etc.