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Tham khảo tài liệu 'accelerated c# 2010 trey nash phần 10', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 15 LAMBDA EXPRESSIONS var expr Expression Func int int .Lambda Func int int Expression.Add n Expression.Constant 1 n Func int int func expr.Compile for int i 0 i 10 i Console.WriteLine func i The bolded lines here replace the single line in the prior example in which the expr variable is assigned the lambda expression n n 1. I think you ll agree that the first example is much easier to read. However this longhand example helps express the true flexibility of expression trees. Let s break down the steps of building the expression. First you need to represent the parameters in the parameter list of the lambda expression. In this case there is only one the variable n. Thus we start with the following var n Expression.Parameter typeof int n Note In these examples I am using implicitly typed variables to save myself a lot of typing and to reduce clutter for readability. Remember the variables are still strongly typed. The compiler simply infers their type at compile time rather than requiring you to provide the type. This line of code says that we need an expression to represent a variable named n that is of type int. Remember that in a plain lambda expression this type can be inferred based upon the delegate type provided. Now we need to construct a BinaryExpression instance that represents the addition operation as shown next Expression.Add n Expression.Constant 1 Here I ve said that my BinaryExpression should consist of adding an expression representing a constant the number 1 to an expression representing the parameter n. You might have already started to notice a pattern. The framework implements a form of the Abstract Factory design pattern for creating instances of expression elements. That is you cannot create a new instance of BinaryExpression or any other building block of expression trees using the new operator along with the constructor of the type. The constructor is not accessible so you must use the static methods on the Expression class to create
