LINQ转换操作

运算符改变输入对象的类型，并在多种不同的应用范围中使用。

转换例子- 查询表达式

C# 代码示例

using System;
using System.Linq;

namespace Operators
{
  class Cast
  {
     static void Main(string[] args)
     {
        Plant[] plants = new Plant[] {new CarnivorousPlant { Name = "Venus Fly Trap", TrapType = "Snap Trap" },
                                      new CarnivorousPlant { Name = "Pitcher Plant", TrapType = "Pitfall Trap" },
                                      new CarnivorousPlant { Name = "Sundew", TrapType = "Flypaper Trap" },
                                      new CarnivorousPlant { Name = "Waterwheel Plant", TrapType = "Snap Trap" }};

        var query = from CarnivorousPlant cPlant in plants
                    where cPlant.TrapType == "Snap Trap"
                    select cPlant;

        foreach (var e in query)
        {
           Console.WriteLine("Name = {0} , Trap Type = {1}",
                             e.Name, e.TrapType);
        }

        Console.WriteLine("\nPress any key to continue.");
        Console.ReadKey();
     }
  }

  class Plant
  {
     public string Name { get; set; }
  }

  class CarnivorousPlant : Plant
  {
     public string TrapType { get; set; }
  }
}

VB 代码示例

Module Module1
  Sub Main()

     Dim plants() As Plant = {New CarnivorousPlant With {.Name = "Venus Fly Trap", .TrapType = "Snap Trap"},
                              New CarnivorousPlant With {.Name = "Pitcher Plant", .TrapType = "Pitfall Trap"},
                              New CarnivorousPlant With {.Name = "Sundew", .TrapType = "Flypaper Trap"},
                              New CarnivorousPlant With {.Name = "Waterwheel Plant", .TrapType = "Snap Trap"}}

     Dim list = From cPlant As CarnivorousPlant In plants
                Where cPlant.TrapType = "Snap Trap"
                Select cPlant

     For Each e In list
        Console.WriteLine("Name = {0} , Trap Type = {1}", e.Name, e.TrapType)
     Next

     Console.WriteLine(vbLf & "Press any key to continue.")
     Console.ReadKey()
  End Sub

  Class Plant
     Public Property Name As String
  End Class

  Class CarnivorousPlant
     Inherits Plant
     Public Property TrapType As String
  End Class

End Module

当在C#或VB上面的代码被编译和执行时，它产生了以下结果：

Name = Venus Fly Trap, TrapType = Snap Trap
Name = Waterwheel Plant, TrapType = Snap Trap

Press any key to continue.