技术开发 频道

Visual Basic 2008中的隐藏特性


    如果加上类型推断,代码就更简单了。

3) 对象初始化(Object Initializers)

    总的来说,在.net framework里,对象初始化是一种类似于把Dim和statement combined整合在一起的表达式。这样使得参数构造器多少让人容易接受一些:

Dim strm As New StreamWriter( _ 

New FileStream("C:\out.txt",FileMode.OpenOrCreate) _

With {.Position = 10})



 
    对象初始化使得创建一个数组对象更加容易:

Dim Capitals() As City = {New City With {.Name = "Antanarivo", .Country = "Madagascar"}, _ 

New City With {.Name = "Belmopan", .Country = "Belize"}, _

New City With {.Name = "Monaco", .Country = "Monaco"}, _

New City With {.Country = "Palau", .Name = "Koror"}}



 
4) Nullable

      Nullable 是一种特性,可能你知道但没有关注过。它是一个基本的.NET 表达式,专门针对nullable类型,主要用于LINQ。Nullable支持你写一段代码,其中的属性以null值传播。例如下面这点代码,在Country type中有个independence property 是nullable date。

Dim virginIslands As New Country With {.Independence = Nothing} 

Dim palau As New Country With {.Independence = #10/1/1994#}



Dim vILength = #8/24/2005# - virginIslands.Independence ' Nothing

Dim pLength = #8/24/2005# - palau.Independence ' 3980.00:00:00








5) LINQ to DataSet

     它意味着你可以不用调用其他数据访问技术就能收获LINQ的好处。先填充一个DataSet,然后就可以对这个DataSet进行查询。

Me.EmployeesTableAdapter.Fill(Me.NORTHWNDDataSet.Employees) 

Dim query = From emp In Me.NORTHWNDDataSet.Employees _

Where emp.Country = "USA" _

Order By emp.HireDate _

Select emp

Me.EmployeesBindingSource.DataSource = query

 
6) 语法提示(Syntax Tooltips)



看看这个是不是很cool?






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