When typing into a listbox the listbox scrolls to the next item with first letter matching the input character. I want to disable/change this behavior.
I implemented a handler for the keypress event and implemented my new behavior, but I don't see any way to remove the old behavior.
How can I disable the default behavior?
Here is the event handler for the keypress event:
Private Sub FooListBox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles FooListBox.KeyPress
If SearchResetTimer.Enabled Then
SearchResetTimer.Stop()
SearchTimer.Stop()
Else
BeginUpdate()
SearchedString = ""
End If
SearchedString = SearchedString & e.KeyChar
SearchResetTimer.Start()
SearchTimer.Start()
End Sub
Private Function SearchFor(listbox As ListBox, target As String) As Integer
For i As Integer = listbox.SelectedIndex To listbox.Items.Count - 1
If listbox.Items(i).ToString().ToLower().StartsWith(target) Then
Return i
End If
Next
For i As Integer = 0 To listbox.SelectedIndex - 1
If listbox.Items(i).ToString().ToLower().StartsWith(target) Then
Return i
End If
Next
Return -1
End Function
Private Sub SearchTimer_Tick(sender As Object, e As EventArgs) Handles SearchTimer.Tick
SearchTimer.Stop()
Dim Found As Integer = SearchFor(FooListBox, SearchedString)
If Found <> -1 Then
FooListBox.SelectedIndex = Found
End If
EndUpdate()
End Sub
Private Sub SearchResetTimer_Tick(sender As Object, e As EventArgs) Handles SearchResetTimer.Tick
SearchResetTimer.Stop()
End Sub
Quick overview: there are two timers, searchTimer that when ticked searches for the string and updates the control, searchResetTimer which resets the searched string and marks the beginning of a new user input.
Note that I am not releasing this code under CC, it is for illustration purposes only
Related
I am working with forms in VB.NET
There is a DatagridView table with a checkbox column.
See the picture below:
I am interested in the question: how to add the line index to the list when clicking in the checkbox (when we activate the checked status), and remove it from the list when we uncheck the checkbox?
Tried the following but this is not the correct solution:
If e.ColumnIndex = chk_column.Index Then
If e.RowIndex >= 0 Then
Try
For Each row As DataGridViewRow In dataGridNames.Rows
Dim cell As DataGridViewCheckBoxCell = TryCast(row.Cells(5), DataGridViewCheckBoxCell)
If cell.Value Is cell.FalseValue Then
bList_indexes.Add(DataGridnames.CurrentCell.RowIndex)
Exit For
Else 'If cell.Value Is cell.TrueValue Then
bList_indexes.RemoveAt(DataGridnames.CurrentCell.RowIndex)
End If
Next
Catch ex As Exception
'Show the exception's message.
'MessageBox.Show(ex.Message)
'Throw New Exception("Something happened.")
End try
End If
End If
Using DataSources allows you to take the logic out of mucking around in DataGridView events. You shouldn't perform [much] business logic on the UI anyways.
Here is the class I used to represent your data.
Public Class ClassWithSelect
Public Property [Select] As Boolean
Public Property Name As String
Public Sub New(s As Boolean, n As String)
Me.Select = s
Me.Name = n
End Sub
End Class
And all the code to set DataSources
Private myDataSource As List(Of ClassWithSelect)
Private selectedIndices As List(Of Integer)
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
myDataSource = Enumerable.Range(65, 10).Select(Function(i) New ClassWithSelect(False, Chr(i).ToString())).ToList()
DataGridView1.DataSource = myDataSource
updateSelectedIndices()
End Sub
Private Sub DataGridView1_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellValueChanged
updateSelectedIndices()
End Sub
Private Sub DataGridView1_CellContentClick(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
DataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit)
End Sub
Private Sub updateSelectedIndices()
selectedIndices = New List(Of Integer)()
For i = 0 To myDataSource.Count - 1
If myDataSource(i).Select Then selectedIndices.Add(i)
Next
ListBox1.DataSource = selectedIndices
End Sub
And the end result
Now you don't need to access the UI to get the indices for further processing as they are in the class-level variable selectedIndices. The UI is meant for user I/O, NOT for storing state.
Note: The event handler was taken from this answer but this answer is also linked as an improvement to the check change handler, but I felt the complexity would distract from my answer. If you find you need to click fast, look into the latter.
Also Note: The method updateSelectedIndices() should have inside it an InvokeRequired check if you plan to perform work off the UI thread
The code below is a program to calculate the BMI using text boxes. I am having an issue however that when I clear one of the text boxes it will throw an exception and freeze the program. I was wondering if anyone had an answer on how to prevent this. I already tried setting my variables to 0 and 1 to see if that was the issue but it does not appear to be.
Private Sub tboxWeight_TextChanged(sender As Object, e As EventArgs) Handles tboxWeight.TextChanged
Weight = 0
Weight = Convert.ToInt64(tboxWeight.Text)
End Sub
Private Sub tboxHFeet_TextChanged(sender As Object, e As EventArgs) Handles tboxHFeet.TextChanged
Height_feet = 0
Height_feet = Convert.ToInt64(tboxHFeet.Text)
Get_BMI(1)
End Sub
Private Sub tboxHInch_TextChanged(sender As Object, e As EventArgs) Handles tboxHInch.TextChanged
Height_Inches = 0
Height_Inches = Convert.ToInt64(tboxHInch.Text)
Get_BMI(1)
End Sub
Private Sub tboxAge_TextChanged(sender As Object, e As EventArgs) Handles tboxAge.TextChanged
Age = Convert.ToDouble(tboxAge.Text)
End Sub
Function Get_BMI(ByVal j As Integer) As Double
BMI = (Weight / (Height_Inches + (Height_feet * 12) ^ 2) * 703)
tboxBMI.Text = Convert.ToString(BMI)
Exit Function
End function
It is because you set a textbox into an integer field, so when the textbox is empty it will throw exception because the textbox doesn't contain a number.
Try using If else statement for each textboxes.
String.IsNullOrEmpty function will be sufficient.
Good/Best practice says, you need to validate the data before performing calculation i.e. Get_BMI(). Below code snippet will help you.
Dim textBoxValue As String
If Not String.IsNullOrEmpty(textBoxValue) Then
If IsNumeric(textBoxValue) Then
End If
End If
I'm creating a AddIn for Autodesk Inventor (3D drawing software), and for the moment I am playing with positional constraints.
I created a custom user menu for quick editing certain values, in this case the elevation and orientation value.
First I used the textbox.textchanged event to change my constraint value. But this was working not 100%. Example when pressing elevation 1000 would change the elevation 4 times ( on per digit ).
Now I went to using the validated event. This works better, BUT I would like to have the textbox to initiate validation when the Enter button is pressed. For this I whipped up this, but it's not correct i'm sure of it. How should I write this correctly?
The code below works but, I would like to have a proper way to achieve the result.
Private Sub tbElevationValue_TextChanged(sender As Object, e As EventArgs) _
Handles tbElevation.Validated
' If the elevation parameter and textbox value are the same
' The sub must be aborted
If CDbl(tbElevation.Text) = oElevationParameter.Value * 10 Then Exit Sub
' Check the entered value
Dim oValue As Double
If tbElevation.Text = "" Then
oValue = 0
tbElevation.Text = 0
Else
oValue = tbElevation.Text
End If
' Set the parameter value
oElevationParameter.Value = oValue / 10
' Update the document
EM_AddIn.StandardAddInServer.m_inventorApplication.ActiveDocument.Update()
End Sub
Private Sub tbOrientation_TextChanged(sender As Object, e As EventArgs) _
Handles tbOrientation.Validated
' If the orientation parameter and textbox value are the same
' The sub must be aborted
If CDbl(tbOrientation.Text) = cRandiansToDegrees(oOrientationParameter.Value) Then Exit Sub
' Check the entered value
Dim oValue As Double
If tbOrientation.Text = "" Then
oValue = 0
tbOrientation.Text = 0
Else
oValue = tbOrientation.Text
End If
' Set the parameter value
oOrientationParameter.Value = cDegreesToRandians(oValue)
' Update the document
EM_AddIn.StandardAddInServer.m_inventorApplication.ActiveDocument.Update()
End Sub
Private Sub OrientationElevationEnterKey_Pressed(sender As Object, e As Windows.Forms.KeyEventArgs) Handles tbElevation.KeyUp, tbOrientation.KeyUp
If e.KeyCode = Windows.Forms.Keys.Enter Then
CType(sender, Windows.Forms.TextBox).Parent.Focus()
CType(sender, Windows.Forms.TextBox).Focus()
End If
End Sub
I think you're on the right way. It can be a pain to register a key_down event for each TextBox object, but your idea is good.
You can set a key_down event listener to your form instead.
Try something like this:
Private Sub Main_KeyDown(sender As Object, e As KeyEventArgs) Handles MyBase.KeyDown
If e.KeyCode = Keys.KeyCode.Enter Then
MyBase.Focus() ' this will cause the currently focused control to validate
End If
End Sub
I need to set the text value of a DataGridView.EditingControl. I've tried
myDGV.EditingControl.Text() = "1/1/2001"
and
myDGV.EditingControl.Text = "1/1/2001"
and
myDGV.EditingControl.Text("1/1/2001")
which causes an InvalidCastException (didn't check that could only be an integer).
There is no Value() property for the control, so how do I set the the value?
(Yes, I've verified that the cell is in edit mode)
You need to handle the EditingControlShowing event.
Private Sub HandleDgvEditingControlShowing(sender As Object, e As DataGridViewEditingControlShowingEventArgs) Handles Dgv.EditingControlShowing
If (TypeOf e.Control Is DataGridViewTextBoxEditingControl) Then
With DirectCast(e.Control, DataGridViewTextBoxEditingControl)
.Text = "1/1/2001"
End With
End If
End Sub
Note that this event will be fired for all editable cells. If you only want to manipulate the edit control for a given column you need to add another condition. Something like this:
If (Me.Dgv.CurrentCell.OwningColumn is Me.DgvFooColumn) Then
If you need to revert the edit from the CellValidating event then store the original value when the edit control is shown.
Private Sub HandleDgvEditingControlShowing(sender As Object, e As DataGridViewEditingControlShowingEventArgs) Handles Dgv.EditingControlShowing
'Cache the edit control text
Me.cachedEditText = e.Control.Text
End Sub
Private Sub HandleDgvCellValidating(sender As Object, e As DataGridViewCellValidatingEventArgs) Handles Dgv.CellValidating
'Ensure that the edit control exists
If (Not Me.Dgv.EditingControl Is Nothing) Then
'Validate the edit
If (Not valid) Then
Me.Dgv.EditingControl.Text = Me.cachedEditText
End If
End If
End Sub
Private cachedEditText As String
I'm migrating an application from VB6 to VB.Net and I found a change in the behavior of the ListBox and I'm not sure of how to make it equal to VB6.
The problem is this:
In the VB6 app, when the ListBox is focused and I type into it, the list selects the element that matches what I type. e.g. If the list contains a list of countries and I type "ita", "Italy" will be selected in the listbox.
The problem is that with the .Net version of the control if I type "ita" it will select the first element that starts with i, then the first element that starts with "t" and finally the first element that starts with "a".
So, any idea on how to get the original behavior? (I'm thinking in some property that I'm not seeing by some reason or something like that)
I really don't want to write an event handler for this (which btw, wouldn't be trivial).
Thanks a lot!
I shared willw's frustration. This is what I came up with. Add a class called ListBoxTypeAhead to your project and include this code. Then use this class as a control on your form. It traps keyboard input and moves the selected item they way the old VB6 listbox did. You can take out the timer if you wish. It mimics the behavior of keyboard input in Windows explorer.
Public Class ListBoxTypeAhead
Inherits ListBox
Dim Buffer As String
Dim WithEvents Timer1 As New Timer
Private Sub ListBoxTypeAhead_KeyDown(sender As Object, _
e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
Select Case e.KeyCode
Case Keys.A To Keys.Z, Keys.NumPad0 To Keys.NumPad9
e.SuppressKeyPress = True
Buffer &= Chr(e.KeyValue)
Me.SelectedIndex = Me.FindString(Buffer)
Timer1.Start()
Case Else
Timer1.Stop()
Buffer = ""
End Select
End Sub
Private Sub ListBoxTypeAhead_LostFocus(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles Me.LostFocus
Timer1.Stop()
Buffer = ""
End Sub
Public Sub New()
Timer1.Interval = 2000
End Sub
Private Sub Timer1_Tick(sender As Object, e As System.EventArgs) Handles Timer1.Tick
Timer1.Stop()
Buffer = ""
End Sub
End Class
As you probably know, this feature is called 'type ahead,' and it's not built into the Winform ListBox (so you're not missing a property).
You can get the type-ahead functionality on the ListView control if you set its View property to List.
Public Function CheckIfExistInCombo(ByVal objCombo As Object, ByVal TextToFind As String) As Boolean
Dim NumOfItems As Object 'The Number Of Items In ComboBox
Dim IndexNum As Integer 'Index
NumOfItems = objCombo.ListCount
For IndexNum = 0 To NumOfItems - 1
If objCombo.List(IndexNum) = TextToFind Then
CheckIfExistInCombo = True
Exit Function
End If
Next IndexNum
CheckIfExistInCombo = False
End Function