c#3.0新特性

public int ID { get; set; }

// 上面的ID属性（自动属性）等同于下面的ID属性

// private int _id;
// public int ID
// {
//     get { return _id; }
//     set { _id = value; }
// }

/// <summary>
/// ObjectInitializers（对象初始化器）的摘要说明
/// </summary>
public class ObjectInitializers
{
public int ID { get; set; }
public string Name { get; set; }

public void ObjectInitializersTest()
{
ObjectInitializers oi = new ObjectInitializers { ID = 1, Name = "webabcd" };

// 上面的oi对象（对象初始化器）等同于下面的oi对象

// ObjectInitializers oi = new ObjectInitializers();
// oi.ID = 1;
// oi.Name = "webabcd";
}
}

/// <summary>
/// CollectionInitializers（集合初始化器）的摘要说明
/// </summary>
public class CollectionInitializers
{
public int ID { get; set; }
public string Name { get; set; }

public void CollectionInitializersTest()
{
List<CollectionInitializers> list = new List<CollectionInitializers>
{
new CollectionInitializers { ID = 1, Name = "webabcd" },
new CollectionInitializers { ID = 2, Name = "webabcdefg" },
new CollectionInitializers { ID = 3, Name = "webabcdefghijklmn" }
};

// 上面的list集合（集合初始化器）等同于下面的list集合

// List<CollectionInitializers> list = new List<CollectionInitializers>();
// list.Add(new CollectionInitializers { ID = 1, Name = "webabcd" });
// list.Add(new CollectionInitializers { ID = 2, Name = "webabcdefg" });
// list.Add(new CollectionInitializers { ID = 3, Name = "webabcdefghijklmn" });
}
}

/// <summary>
/// 扩展方法（类和方法均为static）
/// 使用的时候要引用该类的命名空间
/// </summary>
public static class MyExtensionMethods
{
// this代表扩展方法应用于string类型上
// ToInt32()是将string类型转换为int类型的扩展方法
public static int ToInt32(this string s)
{
int i;
Int32.TryParse(s, out i);

return i;
}

// this代表扩展方法应用于object类型上
// 该扩展方法需要一个类型为System.Collections.IEnumerable的参数
// In()是判断一个object是否存在于一个System.Collections.IEnumerable中的扩展方法
public static bool In(this object o, System.Collections.IEnumerable e)
{
foreach (object i in e)
{
if (i.Equals(o))
{
return true;
}
}

return false;
}
}

string s = "123";
// 使用string的ToInt32()扩展方法
int i = s.ToInt32();
// i == 123

string[] ary = new string[] { "a", "b", "c" };
// 使用object的In()扩展方法
bool b = "b".In(ary);
// b == true

/// <summary>
/// LambdaExpressions（Lambda表达式）的摘要说明
/// </summary>
public class LambdaExpressions
{
public int ID { get; set; }
public string Name { get; set; }

public void LambdaExpressionsTest()
{
List<LambdaExpressions> list = new List<LambdaExpressions>
{
new LambdaExpressions { ID = 1, Name = "webabcd" },
new LambdaExpressions { ID = 2, Name = "webabcdefg" },
new LambdaExpressions { ID = 3, Name = "webabcdefghijklmn" }
};

IEnumerable<LambdaExpressions> l = list.Where(le => le.Name == "webabcd");

// 上面的（Lambda表达式）等同于下面的（匿名方法）

// IEnumerable<LambdaExpressions> l2 = list.Where(delegate(LambdaExpressions le) { return le.Name == "webabcd"; });

// 相关委托
// public delegate TResult Func<T, TResult>(T arg);

// 相关Where扩展方法
// Func<TSource, bool>：接受一个类型为TSource的参数
// Func<TSource, bool>：某个需要满足的条件，返回bool值
// public static IEnumerable<TSource> Where<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
// {
//     foreach (TSource item in source)
//     {
//         if (predicate(item))
//         {
//             yield return item;
//         }
//     }
// }

}
}

/// <summary>
/// QuerySyntax（查询语法）的摘要说明
/// </summary>
public class QuerySyntax
{
public int ID { get; set; }
public string Name { get; set; }

public void QuerySyntaxTest()
{
List<QuerySyntax> list = new List<QuerySyntax>
{
new QuerySyntax { ID = 1, Name = "webabcd" },
new QuerySyntax { ID = 2, Name = "webabcde" },
new QuerySyntax { ID = 2, Name = "webabcdef" },
new QuerySyntax { ID = 2, Name = "webabcdefg" },
new QuerySyntax { ID = 2, Name = "webabcdefgh" },
new QuerySyntax { ID = 2, Name = "webabcdefghi" },
new QuerySyntax { ID = 2, Name = "webabcdefghij" },
new QuerySyntax { ID = 2, Name = "webabcdefghijk" },
new QuerySyntax { ID = 2, Name = "webabcdefghijkl" },
new QuerySyntax { ID = 2, Name = "webabcdefghijklm" },
new QuerySyntax { ID = 3, Name = "webabcdefghijklmn" }
};

IEnumerable<QuerySyntax> l = from o in list
where o.Name.Length > 10
orderby o.Name.Length descending
select o;

// 上面的（查询语法）等同于下面的（LINQ扩展方法和Lambda表达式）
// 查询语法相对更容易理解

// IEnumerable<QuerySyntax> l = list.Where(o => o.Name.Length > 10).OrderByDescending(o => o.Name.Length);

// Projection（映射）
// 可以返回一个新的类型
IEnumerable<Projection> l2 = from o in list
where o.Name.Length > 10
orderby o.Name.Length descending
select new Projection { Name = o.Name };

var l3 = from o in list
where o.Name.Length > 10
orderby o.Name.Length descending
select new { Name=o.Name};
}
}

/// <summary>
/// 为了演示Projection（映射）而写的实体类
/// </summary>
public class Projection
{
public string Name { get; set; }
}

/// <summary>
/// AnonymousTypes（匿名类型）的摘要说明
/// </summary>
public class AnonymousTypes
{
public int ID { get; set; }
public string Name { get; set; }
public int Age { get; set; }

public void AnonymousTypesTest()
{
List<AnonymousTypes> list = new List<AnonymousTypes>
{
new AnonymousTypes { ID = 1, Name = "webabcd", Age = 10 },
new AnonymousTypes { ID = 2, Name = "webabcdefg", Age = 20 },
new AnonymousTypes { ID = 3, Name = "webabcdefghijklmn", Age = 30 }
};

// listAnonymousTypes - 匿名类型
var listAnonymousTypes = from l in list
where l.Name == "webabcd"
select new { Name = l.Name, Age = l.Age };

foreach (var v in listAnonymousTypes)
{
// v - 匿名类型，可以在Visual Studio中得到编译时检查和完整的intellisense
string name = v.Name;
int age = v.Age;
}

// 声明匿名类型：将new关键词后面的类型名称省略掉
var person = new { Name = "webabcd", Age = 27 };
// person - 匿名类型，可以在Visual Studio中得到编译时检查和完整的intellisense
string myName = person.Name;
int myAge = person.Age;
}
}