Access the value of a member expression

Question

If i have a product.

var p = new Product { Price = 30 };

and i have the following linq query.

var q = repo.Products().Where         


        

Answer 1

The constant expression is going to point to a capture-class generated by the compiler. I've not included the decision points etc, but here's how to get 30 from that:

var p = new Product { Price = 30 };
Expression> predicate = x => x.Price == p.Price;
BinaryExpression eq = (BinaryExpression)predicate.Body;
MemberExpression productToPrice = (MemberExpression)eq.Right;
MemberExpression captureToProduct = (MemberExpression)productToPrice.Expression;
ConstantExpression captureConst = (ConstantExpression)captureToProduct.Expression;
object product = ((FieldInfo)captureToProduct.Member).GetValue(captureConst.Value);
object price = ((PropertyInfo)productToPrice.Member).GetValue(product, null);

price is now 30. Note that I'm assuming that Price is a property, but in reality you would write a GetValue method that handles property / field.