I have a CheckedListBox control that I fill with DataGridView Column HeaderText values. If these columns are visible, I would like to set the CheckedListBox Items to "Checked". My code is as follows:
For Each col As DataGridViewColumn In frmTimingP2P.dgvOverview.Columns
If col.Visible = True Then
For Each item In clbOverviewColumnOrder.Items
Dim intItemIndex As Integer = clbOverviewColumnOrder.Items.IndexOf(item)
If col.HeaderText = item.ToString Then
clbOverviewColumnOrder.SetItemCheckState(intItemIndex, CheckState.Checked)
End If
Next
End If
Next
Whenever this code runs, I get the following error:
"List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change."
What causes this? How can I get around this issue?
Thanks
Whenever are doing a for loop through an enumerator, the enumeration can't be modified or it throws this exception.
I'm not certain exactly why the enumeration would be changing here (it could be possible some other parts of your code are reacting to the change in check state) but one way to get around this would be to instantiate an enumerator and then loop through that instead.
I don't know VB, so here's some psuedo code!
e.g.
newEnumerator = ColumnOrder.Items.GetEnumerator()
begin loop through newEnumerator
set checkbox
end loop
So even if the Items list changes, it shouldn't affect this enumerator.
Thanks for the advice. I guess the error was related the the fact that, under some circumstances, you cannot modify a set of controls during a For...Next loop.
I have revised my code and ended up with the following:
Do While intCurrentItemIndex >= 0
Dim strCurrentItem As String = clbOverviewColumnOrder.Items(intCurrentItemIndex)
For Each col As DataGridViewColumn In frmTimingP2P.dgvOverview.Columns
If col.HeaderText = strCurrentItem Then
If col.Visible = True Then
clbOverviewColumnOrder.SetItemCheckState(intCurrentItemIndex, CheckState.Checked)
Else
clbOverviewColumnOrder.SetItemCheckState(intCurrentItemIndex, CheckState.Unchecked)
End If
End If
Next
intCurrentItemIndex -= 1
Loop
Related
Sorry this is weird and silly question but I need a solution of this...
I have 30 textboxes named as Txt1,Txt2,Txt3,...,Txt30
I have to fill textbox as Txt1.text = 0 on button click..
Is there any way like On Button Click
Dim i as Integer
For i = 1 to 30 '----- Possible in string but don't know if possible in textboxes
Txt(i).text = 0
Next
Or I have to write all 30 lines like
Txt1.text = 0
...
Txt30.text = 0
I don't know how this question asked, maybe Question improper.
Thanx in Advance...
If the textboxes are all contained in Controls collection of the Form, then it is really easy to loop over them
For Each(t in Me.Controls.OfType(Of TextBox)())
t.Text = "0"
Of course the advantage of this approach is that you don't have to worry if you add other textboxes to your form. They will be found using the foreach loop without having a fixed top limit.
And, if not all of your textboxes should be included in the loop, then you can simply use the Tag property of the textboxes that you want to use. For example, if you set the Tag property to the string "Y", then you can change the foreach loop to find only the controls with the matching Tag property
For Each t in Me.Controls.OfType(Of TextBox)() _
.Where(Function(x) x.Tag = "Y")
t.Text = "0"
The two solutions above works well if all your textboxes are contained in the same container (Form, GroupBox or Panel), instead, if these textboxes are dispersed in different containers (some in a groupbox, others in a panel etc) then you can build a List(Of TextBox) variable filling it with the textboxes instances and use it when the need arise
Dim myTexts = New List(Of TextBox)() From { Txt1, Txt2, Txt3, ....}
And loop over this variable
You can do as Steve said, but if you have other textboxes that you don't want to edit then there is another way:
For i = 1 to 30
dim found = Me.Controls.Find("Txt" & i, True) '<- the True argument is for recursive search
If Not IsNothing(found) AndAlso found.Length > 0 Then
found(0).Text = "0"
End If
Next
If your textboxes are all in the same control, for example GroupBox, you can do GroupBox.Controls.Find saving CPU resources
I am creating a form in Access which will be used as an order sheet for classroom materials. I have the available resources listed and a text box next to the resource where the user inputs the quantity they desire.
My VBA code checks to see if any entries have been made by using the following. (I am using Nz() to allow for Null results):
QuantCheck = Nz(Box1.Value, 0) + Nz(Box2.Value, 0) + Nz(Box3.Value, 0)
Where "QuantCheck" is the variable I am using in the IF statement which begins the workflow:
If QuantCheck > 0 Then
I would like to clean this up by using some kind of loop statement, however I am not able to extract the .value from a string. I would love something like the following which I could incorporate into a loop:
"Box"&VariableNumber.Value
From what I can tell, I am not able to use a string (concatenated or otherwise) as the base for the .value call.
It is interesting that there is a way to accomplish this when using a SQL statement. I have this elsewhere in the code which works nicely:
SQLStr = "INSERT INTO OrderRequests VALUES (cbSchool, txtName, Title" & x & ".caption, Box" & x & ")"
Here I have a variable "x" which increases with each loop to change the Title line, and the Box line.
Any help is appreciated.
I suggest you use the Tag property of the controls. Put "QuantCheck" in the Tag property of any control you want to include. Then
Function QuantitiesExist(frm As Form) As Boolean
Dim Ctrl As Control
Const sQUANTCHK As String = "QuantCheck"
For Each Ctrl In frm.Controls
If Ctrl.Tag = sQUANTCHK Then
If Nz(Ctrl.Value) > 0 Then
QuantitiesExist = True
Exit For
End If
End If
Next Ctrl
End Function
Now you get self documenting code
If QuantitiesExist(Me) Then
And when you add/delete/change controls, you don't have to edit your code. Just set up new controls with the proper tags.
You could loop through the control on the for checking the names and then if it is the one you wanted take an action on it, is this what you was thinking of?
Dim Ctrl As Control
For Each Ctrl In Me.Controls
If Ctrl.Name = "TxtPath" Then ' "Box" & VariableNumber Then
MsgBox Ctrl.Value
End If
Next
I'm having a really strange issue with the DataGridView control in a VS2008 / .NET 3.5 winforms project. I have a simple form with a grid. In the form constructor I call a function to bind the grind to a DataTable, and then loop through the rows setting the background colour of the last cell to LightGrey and the cell itself to read-only if the column value is true. After the form finishes loading the code didn't work i.e. the cells are not set to LightGrey and are not read-only (even though when I step through the code I can see the properties being set). I then call the function again from a button, but this time the colour is changed to LightGrey and the cell is made read-only i.e. the code works.
CODE:
Dim dgr As DataGridViewRow
For i_DsRow As Integer = 0 To ds.Tables(0).Rows.Count - 1
dr = ds.Tables(0).Rows(i_DsRow)
For i_row As Integer = 0 To DgSearch.Rows.Count - 1
dgr = DgSearch.Rows(i_row)
If dr("DsColoumn1").ToString.ToUpper = dgr.Cells("DgColoumn1").Value.ToString.ToUpper Then
If Val(dr("Coloumn2").ToString) = 3 Then
dgr.Cells("SomeColomname").Value = dr("SomeColoumName2").ToString
If dgr.Cells("SomeColomname3").Value.ToString <> "" Then dgr.Cells("SomeColomname3").Value &= ", "
dgr.Cells("SomeColomname3").Value &= dr("SomeColoumName2").ToString
SetCellColor(dgr.Cells("SomeColomname"), dgr.Cells("SomeColomname3"))
End If
Exit For
End If
Next
Next
Private Sub SetCellColor(ByVal resultCell As DataGridViewCell, ByVal ColorCell As DataGridViewCell)
If resultCell.Value.ToString().ToUpper = "A".ToUpper Or resultCell.Value.ToString().ToUpper = "B".ToUpper Then
ColorCell.Style.BackColor = Color.FromName("Red")
ElseIf resultCell.Value.ToString().ToUpper = "C".ToUpper Or resultCell.Value.ToString().ToUpper = "D".ToUpper Then
ColorCell.Style.BackColor = Color.FromName("MediumSeaGreen")
Else
ColorCell.Style.BackColor = Color.FromName("Yellow")
End If
End Sub
Thanks for adding the code. I would suggest putting all formatting in the CellFormatting event of the DataGridView.
There are a couple of gotchas that you have to watch, which looking at your code shouldn't be a problem but to be aware of:
This runs for each cell in the grid. Therefore Database lookups are a really bad idea.
You do best to get values where possible from the eventargs parameter of the method
If you need a code sample, I believe there are some good c# examples (possibly vb to) this one for example.
I have a winform that has about 6 comboboxes and 3 textboxes. I also have a button that takes the values of aforementioned controls and inserts them into SQL. Is there a better way, than a bunch of nested if/then statements, to verify that the controls all have values before inserting the data? This gets ugly very fast. I have tried googling this answer, but I get too many ASPx answers. I will entertain any ideas you may have. I am just trying to find a better way to do this. Thanks for any help.
I think its not too hard.
This code shows error message about the first empty textbox or combobox. But you can easily modify to show error message for all empty comboboxes and textboxes if required.
Private Function ValidateMyControls() As Boolean
Dim allComboBoxes() As ComboBox = {ComboBox1, ComboBox2, ComboBox3} ' add all your comboboxes here
Dim allTextBoxes() As TextBox = {TextBox1, TextBox2, TextBox3} ' add all your textboxes here
Dim emptyTB As TextBox = allTextBoxes.Where(Function(f) f.Text = "").FirstOrDefault
Dim emptyCB As ComboBox = allComboBoxes.Where(Function(f) f.SelectedIndex = -1).FirstOrDefault
If emptyTB IsNot Nothing Then
MessageBox.Show("Please fill value in " & emptyTB.Name)
Return False
ElseIf emptyCB IsNot Nothing Then
MessageBox.Show("Please select a value in dropdown " & emptyCB.Name)
Return False
Else
' All set to go!
Return True
End If
End Function
I'm using a loop to fill a collection. There are a few properties for each item of the collection, but some of these properties are optional. The user is prompted to choose which properties will be copied to the collection. Is it possible to omit the code for the optional properties if the user has chosen to ignore them?
Sub fillcoll()
Dim coll as Collection
Set coll = New Collection
Dim NewItem as Class1
For each r in Selection.Rows
Set NewItem = New Class1
If Userform1.Checkbox1.Value = True then
NewItem.Property1 = somearray1(r.Row)
End If
If Userform1.Checkbox2.Value = True then
NewItem.Property2 = somearray2(r.Row)
End If
If Userform1.Checkbox3.Value = True then
NewItem.Property3 = somearray3(r.Row)
End If
Next r
End Sub
With this code, the Checkboxes' values are read at each iteration. I fear that this may slow down the program's execution unnecessarily. The checkboxes could be read once and the loop's contents would adapt to the checkboxes' values. Is this possible?
Thanks in advance.
Read the checkboxes at the beginning,out of the loop, and assign their values to three booleans or an array of booleans. then you just read from the boolean variables every time.
this will improve performance since you do not need to access any object variable, but just a boolean that lays inside your class/object.