This example shows how to use LINQ to compare two lists of strings and output those lines that are in names1.txt but not in names2.txt.
To create the data files
- Copy names1.txt and names2.txt to your solution folder as shown in How to: Combine and Compare String Collections (LINQ).
Example
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
*/
Some types of query operations in both C# and Visual Basic, such as Except, Distinct, Union, and Concat<TSource>, can only be expressed in method-based syntax.
Compiling the Code
Create a Visual Studio project that targets the .NET Framework version 3.5. By default, the project has a reference to System.Core.dll and a using directive (C#) or Imports statement (Visual Basic) for the System.Linq namespace. In C# projects, add a using directive for the System.IO namespace.
Copy this code into your project.
Press F5 to compile and run the program.
Press any key to exit the console window.