Partitioning Data (Visual Basic)

Άρθρο
12/22/2021

Partitioning in LINQ refers to the operation of dividing an input sequence into two sections, without rearranging the elements, and then returning one of the sections.

The following illustration shows the results of three different partitioning operations on a sequence of characters. The first operation returns the first three elements in the sequence. The second operation skips the first three elements and returns the remaining elements. The third operation skips the first two elements in the sequence and returns the next three elements.

Illustration that shows three LINQ partitioning operations.

The standard query operator methods that partition sequences are listed in the following section.

Operators

Operator Name	Description	Visual Basic Query Expression Syntax	More Information
Skip	Skips elements up to a specified position in a sequence.	`Skip`	Enumerable.Skip Queryable.Skip
SkipWhile	Skips elements based on a predicate function until an element does not satisfy the condition.	`Skip While`	Enumerable.SkipWhile Queryable.SkipWhile
Take	Takes elements up to a specified position in a sequence.	`Take`	Enumerable.Take Queryable.Take
TakeWhile	Takes elements based on a predicate function until an element does not satisfy the condition.	`Take While`	Enumerable.TakeWhile Queryable.TakeWhile
Chunk	Splits the elements of a sequence into chunks of a specified maximum size.		Enumerable.Chunk Queryable.Chunk

Query Expression Syntax Examples

Skip

The following code example uses the Skip clause in Visual Basic to skip over the first four strings in an array of strings before returning the remaining strings in the array.


Dim words = {"an", "apple", "a", "day", "keeps", "the", "doctor", "away"}

Dim query = From word In words
            Skip 4

Dim sb As New System.Text.StringBuilder()
For Each str As String In query
    sb.AppendLine(str)
Next

' Display the results.
MsgBox(sb.ToString())

' This code produces the following output:

' keeps
' the
' doctor
' away

SkipWhile

The following code example uses the Skip While clause in Visual Basic to skip over the strings in an array while the first letter of the string is "a". The remaining strings in the array are returned.


Dim words = {"an", "apple", "a", "day", "keeps", "the", "doctor", "away"}

Dim query = From word In words
            Skip While word.Substring(0, 1) = "a"

Dim sb As New System.Text.StringBuilder()
For Each str As String In query
    sb.AppendLine(str)
Next

' Display the results.
MsgBox(sb.ToString())

' This code produces the following output:

' day
' keeps
' the
' doctor
' away

Take

The following code example uses the Take clause in Visual Basic to return the first two strings in an array of strings.


Dim words = {"an", "apple", "a", "day", "keeps", "the", "doctor", "away"}

Dim query = From word In words
            Take 2

Dim sb As New System.Text.StringBuilder()
For Each str As String In query
    sb.AppendLine(str)
Next

' Display the results.
MsgBox(sb.ToString())

' This code produces the following output:

' an
' apple

TakeWhile

The following code example uses the Take While clause in Visual Basic to return strings from an array while the length of the string is five or less.


Dim words = {"an", "apple", "a", "day", "keeps", "the", "doctor", "away"}

Dim query = From word In words
            Take While word.Length < 6

Dim sb As New System.Text.StringBuilder()
For Each str As String In query
    sb.AppendLine(str)
Next

' Display the results.
MsgBox(sb.ToString())

' This code produces the following output:

' an
' apple
' a
' day
' keeps
' the

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