Help with Listbox

Question

Can you please tell me how to code for handling the keypress event and capturing when someone
is typing a word in the list (using a listbox)

Thanks

Answer 1

Doing something like the following will allow you to select a particular ListBox item based on the key inputs from the user, supposing the user doesn't stop for 2 seconds before typing another letter. It uses StringBuilder and a Timer to manipulate the values the user types when the ListBox has focus.  It checks the value of the StringBuilder against the items in the ListBox to intelligently select an item.

System.Windows.Forms.Timer timer = new Timer();

private StringBuilder currentSelection = new StringBuilder();

public Form1()

{

InitializeComponent();

timer.Interval = 1000;

timer.Tick += new EventHandler(timer_Tick);

}

void timer_Tick(object sender, EventArgs e)

{

currentSelection.Remove(0, currentSelection.Length);

timer.Stop();

}

private void listBox1_KeyPress(object sender, KeyPressEventArgs e)

{

timer.Stop();

timer.Start();

currentSelection.Append(e.KeyChar);

for (int i = 0; i < listBox1.Items.Count; i++)

{

if (listBox1.Items[i].ToString().ToUpper().StartsWith(currentSelection.ToString().ToUpper()))

{

listBox1.SelectedIndex = i;

break;

}

}

e.Handled = true;

}

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David Morton - http://blog.davemorton.net/

Answer 2

I will try this code in VB 2005, need to first modify to VB 2005

Thanks 

Answer 3

This is the same thing in VB, courtesy of Telerik. (http://converter.telerik.com/)

Private timer As System.Windows.Forms.Timer = New Timer()
Private currentSelection As New StringBuilder()

Public Sub New()
    InitializeComponent()
    timer.Interval = 1000
    AddHandler timer.Tick, AddressOf timer_Tick
End Sub

Sub timer_Tick(ByVal sender As Object, ByVal e As EventArgs)
    currentSelection.Remove(0, currentSelection.Length)
    timer.[Stop]()
End Sub

Private Sub listBox1_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs)
    timer.[Stop]()
    timer.Start()
    currentSelection.Append(e.KeyChar)

    Dim i As Integer = 0
    While i < listBox1.Items.Count
        If listBox1.Items(i).ToString().ToUpper().StartsWith(currentSelection.ToString().ToUpper()) Then
            listBox1.SelectedIndex = i
            Exit While
        End If
        System.Math.Max(System.Threading.Interlocked.Increment(i),i - 1)
    End While
    e.Handled = True
End Sub

---

David Morton - http://blog.davemorton.net/

Answer 4

David;
Using the code you provided works great; but now the user wants to have the ability to type for a particular title and only that title get highlighted (which is what it is doing right now, because the property SelectionMode is set to 'One') and have the ability to use the shift Key and Click to select multiple titles.

When I set the listbox property SelectionMode -> MultiSimple, they can do the shift key and Click for multiple titles without a problem, but when they are typing a title several get highlighted.

Example:
When I click on the listbox and start to type for title 'TRW'  this is what is highlighted:
Apples and Oranges (first in list)
The little Train
Trains
TRW

Is it possible to give them both?

Answer 5

 How can I make this work?
Private Sub listBox1_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs)

If Not e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.ShiftKey) Then

    'e.Handled = True

    listBox1.SelectionMode = SelectionMode.One

    timer.[Stop]()
    timer.Start()
    currentSelection.Append(e.KeyChar)

    Dim i As Integer = 0
    While i < listBox1.Items.Count
        If listBox1.Items(i).ToString().ToUpper().StartsWith(currentSelection.ToString().ToUpper()) Then
            listBox1.SelectedIndex = i
           Exit While
        End If
        System.Math.Max(System.Threading.Interlocked.Increment(i),i - 1)
    End While
    e.Handled = True

Else

    listBox1.SelectionMode = SelectionMode.MultiSimple

End If
End Sub

Answer 6

Set the ListBox's SelectionMode property to SelectionMode.MultiExtended.  This will allow multiple selection of items when the user clicks the control key plus the selected items. 

I'd encourage you to explain to your user that the standard usage of multi-select listboxes is to use the control key, not the shift key.  You can tell them it'll select multiple items just like Windows Explorer.  I don't think they'll have a problem with it.  Using shift+clicking to select multiple items isn't standard UI behavior, using control+clicking is.

---

David Morton - http://blog.davemorton.net/

Answer 7

 Thanks for the help.  I did as you suggested and it works great!!!