如何：查找两个列表之间的差集 (LINQ)
此示例演示如何使用 LINQ 对两个字符串列表进行比较，并输出那些位于 names1.txt 中但不在 names2.txt 中的行。
创建数据文件
- 按照如何：组合和比较字符串集合 (LINQ) 中的说明，将 names1.txt 和 names2.txt 复制到解决方案文件夹中。
示例
Class CompareLists
Shared Sub Main()
' Create the IEnumerable data sources.
Dim names1 As String() = System.IO.File.ReadAllLines("../../../names1.txt")
Dim names2 As String() = System.IO.File.ReadAllLines("../../../names2.txt")
' Create the query. Note that method syntax must be used here.
Dim differenceQuery = names1.Except(names2)
Console.WriteLine("The following lines are in names1.txt but not names2.txt")
' Execute the query.
For Each name As String In differenceQuery
Console.WriteLine(name)
Next
' Keep console window open in debug mode.
Console.WriteLine("Press any key to exit.")
Console.ReadKey()
End Sub
End Class
' Output:
' The following lines are in names1.txt but not names2.txt
' Potra, Cristina
' Noriega, Fabricio
' Aw, Kam Foo
' Toyoshima, Tim
' Guy, Wey Yuan
' Garcia, Debra
class CompareLists
{
static void Main()
{
// Create the IEnumerable data sources.
string[] names1 = System.IO.File.ReadAllLines(@"../../../names1.txt");
string[] names2 = System.IO.File.ReadAllLines(@"../../../names2.txt");
// Create the query. Note that method syntax must be used here.
IEnumerable<string> differenceQuery =
names1.Except(names2);
// Execute the query.
Console.WriteLine("The following lines are in names1.txt but not names2.txt");
foreach (string s in differenceQuery)
Console.WriteLine(s);
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
/* Output:
The following lines are in names1.txt but not names2.txt
Potra, Cristina
Noriega, Fabricio
Aw, Kam Foo
Toyoshima, Tim
Guy, Wey Yuan
Garcia, Debra
*/
C# 和 Visual Basic 中的某些类型的查询操作（如 Except、Distinct、Union 和 Concat<TSource>）只能用基于方法的语法表示。
编译代码
创建一个面向 .NET Framework 3.5 版的 Visual Studio 项目。 默认情况下，该项目具有对 System.Core.dll 的引用以及针对 System.Linq 命名空间的 using 指令 (C#) 或 Imports 语句 (Visual Basic)。 在 C# 项目中，添加 System.IO 命名空间的 using 指令。
将此代码复制到您的项目。
按 F5 编译并运行程序。
按任意键退出控制台窗口。