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How to: Sort or Filter Text Data by Any Word or Field (LINQ) (Visual Basic)

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The following example shows how to sort lines of structured text, such as comma-separated values, by any field in the line. The field may be dynamically specified at run time. Assume that the fields in scores.csv represent a student's ID number, followed by a series of four test scores.

To create a file that contains data

Copy the scores.csv data from the topic How to: Join Content from Dissimilar Files (LINQ) (Visual Basic) and save it to your solution folder.

Example

Class SortLines

    Shared Sub Main()
        Dim scores As String() = System.IO.File.ReadAllLines("../../../scores.csv")

        ' Change this to any value from 0 to 4
        Dim sortField As Integer = 1

        Console.WriteLine("Sorted highest to lowest by field " & sortField)

        ' Demonstrates how to return query from a method.
        ' The query is executed here.
        For Each str As String In SortQuery(scores, sortField)
            Console.WriteLine(str)
        Next

        ' Keep console window open in debug mode.
        Console.WriteLine("Press any key to exit.")
        Console.ReadKey()

    End Sub

    Shared Function SortQuery(
        ByVal source As IEnumerable(Of String),
        ByVal num As Integer) As IEnumerable(Of String)

        Dim scoreQuery = From line In source
                         Let fields = line.Split(New Char() {","})
                         Order By fields(num) Descending
                         Select line

        Return scoreQuery
    End Function
End Class
' Output:
' Sorted highest to lowest by field 1
' 116, 99, 86, 90, 94
' 120, 99, 82, 81, 79
' 111, 97, 92, 81, 60
' 114, 97, 89, 85, 82
' 121, 96, 85, 91, 60
' 122, 94, 92, 91, 91
' 117, 93, 92, 80, 87
' 118, 92, 90, 83, 78
' 113, 88, 94, 65, 91
' 112, 75, 84, 91, 39
' 119, 68, 79, 88, 92
' 115, 35, 72, 91, 70

This example also demonstrates how to return a query variable from a Function.

Compile the code

Create a Visual Basic console application project, with an Imports statement for the System.Linq namespace.

See also