C#3.0和LINQ的新特性.ppt

New Feature of C# 3.0 * Initials Anonymous types new can be used directly with an initializer Compiler synthesizes a type Type properties are accessible as usual Use var to define a variable of any anonymous type New Feature of C# 3.0 * Initials Anonymous types Anonymous types are sealed classes. Anonymous types are visible only in the code block where it is defined. The compiler generates Constructor, GetHashCode()? method and ToString() method automatically for anonymous types. The fields and properties of anonymous types are read-only. Anonymous types are distinguished by the field list, not the signiture. New Feature of C# 3.0 * Initials Lambda expressions Lambda expression is an anonymous function. Lambda functions simplify anonymous methods. Lambda functions declared via new = operator (args) = code block, “=” is read as “goes to” New Feature of C# 3.0 * Initials Two kinds of Lambda expressions Expression Lambdas Returns the result of the expression. (x, y) = x == y; (int x, string s) = s.Length x; Statement Lambdas Resembles an expression lambda. With statement enclosed in braces. Can not be used to create expression trees. New Feature of C# 3.0 * Initials Type Inference in Lambdas The lambda must contain the same number of parameters as the delegate type. Each input parameter in the lambda must be convertible to its corresponding delegate parameter. (The type of parameters can be omitted when the type can be deduced from the context). The return value (if any) must be implicitly convertible to the delegate’s return value. New Feature of C# 3.0 * Initials Other stuff of Lambdas “=” has the same precedence as assignment (=) operator. “=” is right-associative. A return statement in a lambda expression does not cause the enclosing method to return. Lambda expression can not contain a goto statement whose target is outside the body. (same as break and continue) When lambda holds a reference to the outer scope, the reference is not used until the lambda f