using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
namespace NewFeature
{
class Person
{
public int ID;
public int IDRole;
public string FirstName;
public string LastName;
}
static class Extend
{
/// <summary>
/// String Extension Method,transform the white space to underscore.
/// </summary>
/// <param name="s"></param>
/// <param name="isUpper"></param>
/// <returns></returns>
public static string SpaceToUnderscore(this string s, bool isUpper) //Extension Method,Notice [this] position
{
char[] charArray = s.ToCharArray();
string result = null;
foreach (char c in charArray)
{
if (char.IsWhiteSpace(c))
result += "_";
else
result += c;
}
return isUpper ? result.ToUpper() : result;
}
}
class Program
{
static void Main(string[] args)
{
CSharpNewFeatures();
QueryAsMethod();
Console.ReadKey();
}
static void CSharpNewFeatures()
{
//(1),Extension Method
string str = "I'm jerry chou";
Console.WriteLine("Extesion Method for string:\n{0}\n",str.SpaceToUnderscore(true));
//(2),Lambda Expressions
// delegate void Action(void);
Action doAction = delegate() { Console.WriteLine("I'm nothing, just use Anonymous Method"); };
Action doLambdaAtion = () => { Console.WriteLine("I'm anything, just use Lambda Expression\n"); };
doAction();
doLambdaAtion();
//(3),Expression Tree
Expression<Func<Person, bool>> e = p => p.ID == 1;
BinaryExpression body = e.Body as BinaryExpression;
MemberExpression left = body.Left as MemberExpression;
ConstantExpression right = body.Right as ConstantExpression;
Console.WriteLine("Expression Tree:\n{0}",left.ToString());
Console.WriteLine(body.NodeType.ToString());
Console.WriteLine(right.Value.ToString() + "\n");
//(4),Anonymous Types,
//(5),use Object Initializaion Expressions
object obj = new { LastName = "Anderson", FirstName = "Brad" };
object obj2 = new { LastName = "Jerry", Age = 26, IsMale = true };
Console.WriteLine("Type:\t{0}\nToString:\t{1}", obj.GetType(), obj.ToString());
Console.WriteLine("Type:\t{0}\nToString:\t{1}\n", obj2.GetType(), obj2.ToString());
//(6),Implicitly Typed Local Variables
var itlv = new { LastName = "Jerry", Age = 26, IsMale = true };
Console.WriteLine("Implicitly Typed Loca Variables({0}):\nLast Name[{1}]\tAge[{2}]\tIsMale[{3}]\n",itlv.GetType(), itlv.LastName, itlv.Age, itlv.IsMale);
//itlv.Age = 99; //Anonymous Type cannot be assigned to -- it is read only
}
/// <summary>
/// LINQ中SQOs(Standard Query Operators)，最终会在Compile-Time被编译器转换为函数调用
/// </summary>
static void QueryAsMethod()
{
string sentence = "the quick brown fox jumps over the lazy dog";
// Split the string into individual words to create a collection.
string[] words = sentence.Split(' ');
// Using query expression syntax.
var query = from word in words
group word.ToUpper() by word.Length into gr
orderby gr.Key
select new { Length = gr.Key, Words = gr };
// Using method-based query syntax.
var query2 = words.
GroupBy(w => w.Length, w => w.ToUpper()).
Select(g => new { Length = g.Key, Words = g }).
OrderBy(o => o.Length);
foreach (var obj in query)
{
Console.WriteLine("Words of length {0}:", obj.Length);
foreach (string word in obj.Words)
Console.WriteLine(word);
}
// This code example produces the following output:
//
// Words of length 3:
// THE
// FOX
// THE
// DOG
// Words of length 4:
// OVER
// LAZY
// Words of length 5:
// QUICK
// BROWN
// JUMPS
}
}
}
原文：http://blog.chinaunix.net/u/11680/showart_1414688.html