I have a combo box that has a couple items in them, where they add text to a text box. I want to prevent the same item being selected twice in a row, because the index never changed, but it still runs the code.
Here's what I've done:
Dim intComboIndex As Integer = -1
Dim cboComboBox As ComboBox = CType(sender, ComboBox)
Dim intComboSelIndex As Integer = cboComboBox.SelectedIndex
If intComboSelIndex > -1 And intComboSelIndex <> intComboIndex Then intComboIndex = intComboSelIndex
Is there a more efficient way of doing this, without having to create a different combo box and compare the indexes?
You must store the previously selected index elsewhere, because at the moment you recreate the variable every time the event is raised.
I'd recommend storing the previously selected index at class level, and then compare that to the currently selected index.
Public Class Form1
Dim ComboBoxPrevIndex As Integer = -1 'Declared at class level, outside any Sub or Function.
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
Dim SenderBox As ComboBox = DirectCast(sender, ComboBox) 'Get the control that raised the ever.
'Has the selection changed?
If ComboBoxPrevIndex <> SenderBox.SelectedIndex _
AndAlso SenderBox.SelectedIndex > -1 Then
'Do stuff...
End If
ComboBoxPrevIndex = SenderBox.SelectedIndex 'Set the new, previous index.
End Sub
End Class
You might have noticed that I used AndAlso instead of And. This is because of AndAlso is short-circuited, meaning that it will only check the condition on it's right if the condition on it's left evaluates to True.
Related
I have a CheckedListBox of 10 names A to J (it's a string but here I'm just using abc), and I want to make it so that every time a user check something, the text will be shown in the listbox simultaneously. I have tried this:
For i = 0 To chklistbxDrugAvailableList.Items.Count - 1
Dim drugs As String = CType(chklistbxDrugAvailableList.Items(i), String)
If chklistbxDrugAvailableList.GetItemChecked(i) Then
listbxYourOrder.Items.Add(drugs)
End If
'drugs = nothing
Next
But when I check A,B,C the text in the Listbox got repeated like so:
A
A
B
A
B
C
I don't know why this is happening. I didn't declare drugs as an array. Even when I used the drugs = nothing, it still give repeated values.
What should I do? Sorry if this is a noob question.
Here is how I would do the whole thing:
Private Sub CheckedListBox1_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles CheckedListBox1.ItemCheck
'Clear the current ListBox contents.
ListBox1.Items.Clear()
'Get the indexes of the currently checked items.
Dim checkedIndices = CheckedListBox1.CheckedIndices.Cast(Of Integer)()
'Add the current index to the list if the item is being checked, otherwise remove it.
checkedIndices = If(e.NewValue = CheckState.Checked,
checkedIndices.Append(e.Index),
checkedIndices.Except({e.Index}))
'Get the checked items in order and add them to the ListBox.
ListBox1.Items.AddRange(checkedIndices.OrderBy(Function(n) n).
Select(Function(i) CheckedListBox1.Items(i)).
ToArray())
End Sub
or like this:
Private Sub CheckedListBox1_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles CheckedListBox1.ItemCheck
'Get the indexes of the currently checked items.
Dim checkedIndices = CheckedListBox1.CheckedIndices.Cast(Of Integer)()
'Add the current index to the list if the item is being checked, otherwise remove it.
checkedIndices = If(e.NewValue = CheckState.Checked,
checkedIndices.Append(e.Index),
checkedIndices.Except({e.Index}))
'Get the checked items in order and add them to the ListBox.
ListBox1.DataSource = checkedIndices.OrderBy(Function(n) n).
Select(Function(i) CheckedListBox1.Items(i)).
ToArray()
End Sub
The difference is that, because the second option uses data-binding, the first item in the ListBox will be selected by default.
The reason that it needs to be a bit verbose is that the ItemCheck event is raised before the item is checked or unchecked. For that reason, we need to get the currently checked items first and then either add or remove the current item, depending on whether the current item is being checked or unchecked.
EDIT:
Here's an option that doesn't require clearing the ListBox:
Private Sub CheckedListBox1_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles CheckedListBox1.ItemCheck
Dim item = CheckedListBox1.Items(e.Index)
If e.NewValue = CheckState.Checked Then
ListBox1.Items.Add(item)
Else
ListBox1.Items.Remove(item)
End If
End Sub
The issue with that is that the items will appear in the ListBox in the order you checked them, rather than the order they appear in the CheckedListBox. The other options keep the items in the same order in both lists.
If I understand your question I would this:
lstbxYourOrder.Items.Clear()
For Each l As String In chklistbxDrugAvailableList.CheckedItems
listbxYourOrder.Items.Add(l)
Next
I am building a large data entry form and want to enable or disable groups of comboboxes based on a checkbox ( if the check box gets checked, the collection of combo boxes get enabled for user input and vice versa ). I want to use collection, because the comboboxes are not always going to be in sequential order ( example : Comboboxes 1-7, then Combobox 12, then 16, and 45-57 ). A collection seems ideal.
I've built the collections, added the comboboxes, and added items to the comboboxes. All the items are there in the comboboxes when I run the Application. I can enable or disable them individually, but I can't enable/disable the comboboxes as a collection.. how can I enable or disable them as a group ?
I can get this to work if I select all the combo boxes in my form, and then run the thru list matching the names against a variable ( as an example, for boxes 1 - 56 ), but that makes using a collection redundant. I am also going to want to output the data, in the collection groups, for later use.
I've been beating my head against the wall for a day or so on this..
Declare Collection
Dim CablesCollectionBoxes As New Collection
Add Comboboxes to collection
CablesCollectionBoxes.Add(ComboBox1)
CablesCollectionBoxes.Add(ComboBox2)
CablesCollectionBoxes.Add(ComboBox3)
.
<removed for space and readability>
.
CablesCollectionBoxes.Add(ComboBox56)
I am trying modify the collection of ComboBoxes to a disabled state, but the code below won't work.
for I as integer = 1 to 56
CablesCollectionBoxes.Item(i) = Disabled
next
It DOES work if I use this, but I'm not using the collection, I am running thru ALL the comboboxes and matching names :
For i As Integer = 1 To 56
Dim clsCombo As ComboBox = DirectCast(Me.Controls.Find("ComboBox" & i.ToString(), True)(0), ComboBox)
clsCombo.Enabled = True
Next
or this
ComboBox1.Enabled = True
ComboBox2.Enabled = True
ComboBox3.Enabled = True
ComboBox4.Enabled = True
.
<removed for space and readability>
.
ComboBox56.Enabled = True
How do I access the comboboxes as a group, and change the properties ? Did I declare the collection incorrectly ?
Don't use collection. Collections are soft-deprecated. Use List(Of T)
Dim comboList As New List(Of ComboBox)()
comboList.Add(cbo1)
comboList.Add(cbo2)
comboList.Add(cbo3)
' Imports System.Linq
comboList.ForEach(Sub(cbo) cbo.Enabled = True)
This is as close as you can get.
Now, if you want to have some selective way to enable/disable or whatever, you can use Tag property to mark and then it will look like this
comboList.Where(Function(cbo) cbo.Tag IsNot Nothing AndAlso CBool(cbo.Tag)).ToList().ForEach(Sub(cbo) cbo.Enabled = True)
Be sure that the check box and the enabled property of the combos are in syn when the program starts. Use the designer.
Private ComboCollection As New List(Of ComboBox)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BuildCBCollection()
End Sub
Private Sub BuildCBCollection()
For Each ctrl As Control In Me.Controls
If TypeOf (ctrl) Is ComboBox Then
ComboCollection.Add(CType(ctrl, ComboBox))
End If
Next
End Sub
Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
For Each cb In ComboCollection
cb.Enabled = Not cb.Enabled
Next
End Sub
I am here to find out is it possible to complete my idea to save me time writing long code.
I have 1 main combobox with various items and some other comboboxed. Each combobox of them is called "Combo" + the item from the main combobox.
and I wonder can I, when I click on an item to hide the last used combobox and to show the combobox linked to this item?
1. hide last used combobox
2. show the combobox responding to the selected item from the main combox
Public Sub ComboBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedIndexChanged
Dim SelectedAction As String = "Combo" + ComboBox2.Text
lastcombobox.visible = false
' now to assign to the new combobox
lastcombobox = (SelectedAction as name of combobox) combobox
Lastcombobox.visible = true
End Sub
Strings are not controls. Strings are the data type of Control.Name; that is the Name property of the control object. You cannot cast a string to a control but all is not lost. Create your other Combo Boxes at design time and stack them on top of each other. Notice the Static keyword before lastComboBox. This persists the value between calls to the method. You could accomplish the same thing by making this variable a class level variable. The first time the method is called their will be nothing in lastComboBox therefore the check for IsNothhing. Control.Find returns an array so we must refer to ctl(0) - the first element of the array, since we know it will return only one.
Private Sub Combo2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles Combo2.SelectedIndexChanged
Dim SelectedAction As String = "Combo" & Combo2.Text
Static lastComboBox As ComboBox
If Not IsNothing(lastComboBox) Then
lastComboBox.Visible = False
End If
Dim ctl() As Control = Controls.Find(SelectedAction, True)
lastComboBox = CType(ctl(0), ComboBox)
lastComboBox.BringToFront()
lastComboBox.Visible = True
End Sub
I have a datagridview with two textbox columns and one combobox column. The combobox's DataSource is bound to enums for the values of the dropdown. The datagridview's DataSource is bound to a custom class with datatypes of string, string and enum.
The first two columns are pre-populated with values and in the third column the user must select a value from the dropdown. All this is working excellent so far except....
The combobox field should be a one-to-one kind of mapping, meaning no two comboboxes should have the same value. I am really not sure how to implement this kind of behavior. Should the chosen value be removed from the remaining dropdowns? should the chosen value remain in the dropdown and just give an error when two of the same are selected?
Any ideas and how to implement these ideas will be of great help.
Thanks
note the only acceptable value that can be used more than once is 'None'
I have an idea based off your intent to possibly remove the chosen value from the remaining dropdowns.
I have a class called Runner which has a similar setup to your example.
Public Class Runner
Public Property FirstName As String
Public Property LastName As String
Public Property Placement As Result
Public Sub New(fn As String, ln As String)
FirstName = fn
LastName = ln
Placement = Result.None
End Sub
End Class
I also have an enum called Result which will get populated into the ComboBoxCell:
Public Enum Result
None = 0
Bronze = 1
Silver = 2
Gold = 3
End Enum
When I create data objects and bind them to the DataGridView, I do so like this (note - Placements is a global List(Of Result) and Runners is a global List(Of Runner):
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Placements.Add(Result.None)
Placements.Add(Result.Bronze)
Placements.Add(Result.Silver)
Placements.Add(Result.Gold)
Runners.Add(New Runner("John", "Smith"))
Runners.Add(New Runner("Jane", "Doe"))
Runners.Add(New Runner("Bill", "Jones"))
Column1.DataPropertyName = "FirstName"
Column2.DataPropertyName = "LastName"
Column3.DataPropertyName = "Placement"
Column3.DataSource = Placements
DataGridView1.DataSource = Runners
End Sub
Now, whenever the value of a cell in the ComboBoxColumn changes, you remove the new value from the list that contains the enums:
Private Sub DataGridView1_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellValueChanged
If (e.RowIndex > -1 And e.ColumnIndex = 2) Then
Dim currentvalue As Result = DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value
If currentvalue <> Result.None Then
Placements.Remove(currentvalue)
End If
End If
End Sub
Be careful when changing drop down selections... as per this Discussion, you have to trick the DataGridView into committing values as soon as the ComboBox value changes. I used an answer from that discussion and did something like this:
Private Sub DataGridView1_CurrentCellDirtyStateChanged(sender As Object, e As EventArgs) Handles DataGridView1.CurrentCellDirtyStateChanged
Dim col As DataGridViewColumn = DataGridView1.Columns(DataGridView1.CurrentCell.ColumnIndex)
If col.Name = "Column3" Then
DataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit)
Dim selected As DataGridViewCell = DataGridView1.CurrentCell
DataGridView1.CurrentCell = Nothing //This line and the next one simply hide
DataGridView1.CurrentCell = selected //an odd display effect that occurs
//because we remove a value and change the
//selection at the same time
End If
End Sub
Finally, you want to handle the DataError event for the DataGridView and leave it blank so that you don't get Exceptions thrown at you when removing values from your list of enums.
This gets you about 90% of the way there. It will not re-add items to the list when you change a value. For example if I change from Gold to Silver, Gold should be added back to the list. You can probably figure out what events to handle to get the old value and the new one, and insert the old value back into the list at the correct index based on its enum value.
I decided to use the CellValidating event of the DataGridView to check whether or not the same value is selected more than once. If it is then a error message is displayed in the row header column.
The combobox in error will not lose focus until the error is resolved.
Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
Dim headerText As String = DataGridView1.Columns(e.ColumnIndex).HeaderText
'Abort validation if cell is not in the Mapping column.
If Not headerText.Equals("Column Mapping") Then Return
'Clear error on current row.
DataGridView1.Rows(e.RowIndex).ErrorText = Nothing
e.Cancel = False
Dim newMappingValue As XmlElement = DirectCast([Enum].Parse(GetType(XmlElement), e.FormattedValue), XmlElement)
' Abort validation if cell value equal XmlElement.None
If newMappingValue.Equals(XmlElement.None) Then Return
For Each dgvRow As DataGridViewRow In DataGridView1.Rows
Dim currentMappingValue As XmlElement = dgvRow.Cells.Item(headerText).Value
If dgvRow.Index <> e.RowIndex Then
If currentMappingValue.Equals(newMappingValue) Then
DataGridView1.Rows(e.RowIndex).ErrorText = "Value already selected, please select a different value."
e.Cancel = True
End If
End If
Next
End Sub
How can I select a single cell from selected row in datagridView and after selecting that I want to put simple search functionality (like we have in our windows folders-typing any characters and search should work)?
I do not really understand your question. If you want to select one cell, you can use the celldoubleclick event for exemple. And the to get the selected cell, use e.rowindex and e.columnindex which will give you the row and the column where the cell is located.
You can try this as a possible solution.
Dim nwData as CustomersDataSet = CustomersDataSet.GetCustomers()
m_CustomersGrid.DataSource = m_CustomersBindingSource
m_CustomersBindingSource.DataSource = nwData.Customers
Then you can sort using the BindingSource.
CustomersBindingSource.Sort = "ContactName ASC"
And you can find using the BindingSource.
Dim index as integer = _
CustomersBindingSource.Find("CompanyName", CompanyNameTextBox.Text)
If index <-1 then 'it was found; move to that position
CustomersBindingSource.Position = index
End If
You could then populate:
CustomersBindingSource.Find("CompanyName", CompanyNameTextBox.Text)
with the keys pressed in the cell by capturing them by utilizing:
Private Sub DataGridView1_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles DataGridView1.KeyUp
Dim dgv As DataGridView = TryCast(sender, DataGridView)
If dgv IsNot Nothing Then
'You will need some logic here to determine how long to wait between keyups
'Perhaps a timer that ticks every500 milliseconds and reset on keyup.
e.KeyData
End If
End Sub
I found the original Biding Source Logic at : This Location