How to check elements from an array in a CheckListBox - vb.net

Question

i have a checklisbox with some value, let's say
"Apple"
"Peach"
"Lemon"
These values came from a dataset.
I have an array with Apple and Lemon: {"Apple", "Lemon"}.
How to check in the checklistbox each value read in this array?
EDIT: In my case, the checklistbox was populate using a dataset provided by a SQL query

Answer 1

In the following code sample, data from SQL-Server (database doesn't matter but this is what I used, what is important is the container the data is loaded into is loaded into a list.
Container to hold data
Public Class Category
Public Property Id() As Integer
Public Property Name() As String
Public Overrides Function ToString() As String
Return Name
End Function
End Class
Class to read data
Imports System.Data.SqlClient
Public Class SqlOperations
Private Shared ConnectionString As String =
"Data Source=.\SQLEXPRESS;Initial Catalog=NorthWind2020;Integrated Security=True"
Public Shared Function Categories() As List(Of Category)
Dim categoriesList = New List(Of Category)
Dim selectStatement = "SELECT CategoryID, CategoryName FROM Categories;"
Using cn As New SqlConnection With {.ConnectionString = ConnectionString}
Using cmd As New SqlCommand With {.Connection = cn}
cmd.CommandText = selectStatement
cn.Open()
Dim reader = cmd.ExecuteReader()
While reader.Read()
categoriesList.Add(New Category() With {.Id = reader.GetInt32(0), .Name = reader.GetString(1)})
End While
End Using
End Using
Return categoriesList
End Function
End Class
Extension method
Which can check or uncheck a value if found in the CheckedListBox and is case insensitive.
Public Module Extensions
<Runtime.CompilerServices.Extension>
Public Function SetCategory(sender As CheckedListBox, text As String, Optional checkedValue As Boolean = True) As Boolean
If String.IsNullOrWhiteSpace(text) Then
Return False
End If
Dim result = CType(sender.DataSource, List(Of Category)).
Select(Function(item, index) New With
{
Key .Column = item,
Key .Index = index
}).FirstOrDefault(Function(this) _
String.Equals(this.Column.Name, text, StringComparison.OrdinalIgnoreCase))
If result IsNot Nothing Then
sender.SetItemChecked(result.Index, checkedValue)
Return True
Else
Return False
End If
End Function
End Module
Form code
Public Class ExampleForm
Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
CheckedListBox1.DataSource = SqlOperations.Categories
End Sub
Private Sub CheckCategoryButton_Click(sender As Object, e As EventArgs) Handles CheckCategoryButton.Click
CheckedListBox1.SetCategory(CategoryToCheckTextBox.Text, StateCheckBox.Checked)
End Sub
End Class
To check all at once
Private Sub CheckAllButton_Click(sender As Object, e As EventArgs) Handles CheckAllButton.Click
CType(CheckedListBox1.DataSource, List(Of Category)).
ForEach(Sub(cat) CheckedListBox1.SetCategory(cat.Name, True))
End Sub

Answer 2

You haven't mentioned exactly how the CheckedListBox gets populated by the DataSet, I've made the assumption that you add Strings directly to the Items collection.
This code will simply loop through the CheckedListBox and compare the values with the array, whatever the match result, the Checkbox is either ticked or cleared.
Dim theArray() As String = {"Apple", "Lemon"}
For counter As Integer = 0 To CheckedListBox1.Items.Count - 1
Dim currentItem As String = CheckedListBox1.Items(counter).ToString
Dim match As Boolean = theArray.Contains(currentItem.ToString)
CheckedListBox1.SetItemChecked(counter, match)
Next

Answer 3

Use the SetItemChecked method like this:
CheckedListBox1.SetItemChecked(CheckedListBox1.Items.IndexOf("your item goes here"), True)
Note that if the item does not exist, an exception will be thrown, so be sure to check for the item before calling the SetItemChecked() method. To do that, you can check for the return value of IndexOf(). It will be -1 if the item does not exist.