LINQ 於 VB.NET

有一些讀者問起,[極意之道-.NET Framework 3.5 資料庫開發聖典]是否會有VB.NET版本,

這點要視出版社而定,一般來說,如果該書一刷尚未賣完,出版社不太可能會投入資金來出版

同一主題,但不同語言的書,所以會不會有VB.NET 版本,得看銷量而定.

anywhere,我其實一直都有個計畫,就是將此書中的範例改寫為VB.NET版本,如果VB.NET版能

順利出版的話,那範例可以放在該書中.

如果出版社在一刷賣完後,仍不願讓我出版VB.NET版,那麼屆時我可以將範例放在BLOG中,供

買了此書之VB.NET讀者下載.

其實,就LINQ語法上來說,VB.NET與C#差異並不大,請見以下程式即可明瞭

Imports System.Linq Public Class Program Shared Sub Main() TestJoin() End Sub 'let 運算子 Shared Sub UseLet() Dim list As String() = {"Code6421 Huang", "Tom Do", "Cathy Chang"} Dim result = From s1 In list _ Let words = s1.Split(" ") _ From word In words _ Let w = word.ToLower() _ Where w(0) = "c" _ Select word For Each item In result Console.WriteLine(item) Next Console.ReadLine() End Sub 'lambda expression for vb.net Shared Sub TestLastWithCondition() Dim numbers() = {8, 9, 10, 7} Console.WriteLine(numbers.Last(Function(x) x > 7)) Console.ReadLine() End Sub ' 匿名型別 'join 運算式 Shared Sub TestJoin() Dim p1() = {New With {.Name = "code6421", .Address = "Taipai"}, _ New With {.Name = "tom", .Address = "Taipai"}, _ New With {.Name = "jeffray", .Address = "NY"}} Dim p2() = {New With {.Name = "code6421", .Title = "Manager"}, _ New With {.Name = "tom", .Title = "Director"}, _ New With {.Name = "jeffray", .Title = "Programmer"}} Dim p3() = {New With {.Name = "code6421", .Hand = "Right"}, _ New With {.Name = "tom", .Hand = "Right"}, _ New With {.Name = "jeffray", .Hand = "Left"}} Dim p4 = From s In p1 _ Join s1 In p2 On s.Name Equals s1.Name _ Join s2 In p3 On s.Name Equals s2.Name _ Select New With {.Name = s.Name, .Address = s.Address, .Title = s1.Title, .Hand = s2.Hand} For Each item In p4 Console.WriteLine("Name {0}, Address {1}, Title {2}, Hand {3}", item.Name, item.Address, item.Title, item.Hand) Next Console.ReadLine() End Sub End Class

差別較大的是,TestLastWithCondition程序中的lambda寫法,及TestJoin中的Select new(匿名型別)之寫法.