VB2010新特性

1.取消了连接符
（1）","之后
（2）"()"前后
（3）"{}"前后
（4）XML
（5）连接字符"&"后
（6）赋值符号"=","&=",":=","+=","-=","*=","/=","=","^=","<<=",">>="后
（7）式内の二項演算子"+","-","/","*","Mod","<>","<",">","<=",">=","^",">>","<<","And","AndAlso","Or","OrElse","Like","Xor",后
（8）Is,IsNot后
（9）成员修饰符"."后
（10）XML的关键字".",".@","...",后
（11）属性标记的前后
（12）查询关键字的前后
（13）For Each的In关键字后
（14）集合的From关键字后

2.自动执行属性 - 为getter和setter省略的属性

Private _name As String
Public Property Name() As String
Get
Return _name
End Get
Set(ByVal value As String)
_name = value
End Set
End Property

Public Property Name As String

3.初始化数组，使用From{元素}方式给集合对象赋初始值

Dim statuses As New Dictionary(Of Integer, String)

statuses.Add(1, "申请")
statuses.Add(2, "科长确认")
statuses.Add(3, "部长确认")
statuses.Add(50, "已确认")
statuses.Add(80, "返回")
statuses.Add(99, "否决")

Dim statuses As New Dictionary(Of Integer, String) From
{
{1, "申请"},
{2, "科长确认"},
{3, "部长确认"},
{50, "已确认"},
{80, "返回"},
{99, "否决"}
}

' 定义
Public Class OS
Public Property Version As Single
Public Property Name As String
End Class

……省略……

' 变量的定义
Dim oses As New List(Of OS) From
{
New OS With {.Name = "Windows XP", .Version = 5.1},
New OS With {.Name = "Windows Vista", .Version = 6},
New OS With {.Name = "Windows 7", .Version = 6.1}
}

4.定义多行Lambda表达式

Dim r = 20.0
Dim pi = Function(birthday As Date)
If birthday.Year > 1990 AndAlso
    birthday.Year < 2000 Then
    Return 3
Else
    Return 3.14
End If
End Function
Console.WriteLine(pi(Date.Today) * r * r)

5.协变性和逆变性
协变性（协方差）意味着你可以为一个参数，一个子类型或继承自已定义类型的某些事物使用更多的派生类型，
逆变性意味着只能使用更少的类型，
因为.NET中的一切都派生自对象，因此你可以使用对象替换一个参数。

' 人
Public Class Person
Public Property Name As String
Public Property Age As Integer
End Class

' 员共 - 继承于人
Public Class Employee
Inherits Person
End Class

' 顾客 - 继承于人
Public Class Customer
Inherits Person
End Class

' 协变性的例子，将员工(Employee)的实例赋值于人(Person)
Dim sato As New Employee With {.Name = "刘英", .Age=32}
Dim man As Person = sato

Class Pet
Public Name As String
End Class

Class NameCompare
Implements IComparer(Of Pet)
' ...
End Class

Class Dog
Inherits Pet
End Class

Class Cat
Inherits Pet
End Class

Module Module1
Sub Main()
Dim DogNames As New SortedList(Of Dog, Object)(New NameCompare)
Dim CatNames As New SortedList(Of Cat, Object)(New NameCompare)
End Sub
End Module

' 逆变性的例子，
'VB2008中，需要传递IComparer(Of Dog)或IComparer(Of Cat)，利用逆变性传递IComparer(Of Pet)就可以

6.动态对象

' 无需定义直接读取MaxRetry属性的值
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="MaxRetry" value ="10" />
</appSettings>
</configuration>

Dim appSettings As Object = New SettingManager()
Console.WriteLine(appSettings.MaxRetry)

' 继承DynamicObject，重写TryGetMember方法
Public Class SettingManager
Inherits DynamicObject

' Get访问属性
Public Overrides Function TryGetMember(ByVal binder As System.Dynamic.GetMemberBinder, ByRef result As Object) As Boolean
result = System.Configuration.ConfigurationManager.AppSettings(binder.Name)
Return True
End Function
End Class


' 可以动态执行属性或方法
Dim user As Object = New ExpandoObject

user.Name = "赵鹏"
user.Show = Sub()
Console.WriteLine(user.Name)
End Sub
user.Show.Invoke()
CType(user, IDictionary(Of String, Object)).Remove("Name")