I have several label boxes on my design form that all share the naming convention lbl_#.text where # ranges from 1 to 60. I want to make a loop that iterates through each lbl_#.text adding some incremental value, let's say multiples of 2 for this question's theoretical purpose.
Something such that the end result would amount to the following:
lbl_1.text = "2"
lbl_2.text = "4"
lbl_3.text = "6"
...
lbl_60.text = "120"
I'm not sure how to access each of these labels through the coding side, I only know how to explicitly mention each label and assign a value :/
There are a few options here.
In this situation the labels will often have a common container, such as panel or groupbox control. In that case:
Dim formLabels = myContainerControl.Controls.OfType(Of Label)()
For Each formLabel As Label In formLabels
'...
Next formLabel
Of course, this mixes logical groups with visual groupings. Those two things don't always align well, so you can also...
Add them all to a Label array (or List(Of Label) or any other enumerable):
Dim formLabels(60) As Label = {lbl_1, lbl_2, lbl_3 .... }
For Each formLabel As Label in formLabels
'...
Next formLabel
But sometimes that's more trouble than it's worth, even if you use a loop to create the collection, and so you can also
Use the .Name property (in conjunction with a naming convention to identify your desired controls):
Dim formLabels = Controls.Where(Function(c) c.Name.StartsWith("lbl_"))
For Each formLabel As Label In formLabels
'...
Next formLabel
Some combination of the above (for example, code in the form load event to create a list based on the name property).
Notice the actual For Each loop is exactly the same in all of those options. No matter what you do, get to the point where you can write a single expression to identify the label control, and then run a simple loop over the expression result.
This points to a final strategy: think in terms of binding to a data source. With a data source, your labels are created as part of a DataGridView, FlowLayoutPanel, or similar control. Then you can iterate the rows in the grid or panel.
Use the Controls collection:
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim i As Integer
For i = 1 To 3
Dim myLabel As Label = CType(Me.Controls("lbl_" & i), Label)
myLabel.Text = ...whatever value you want to put here
Next
End Sub
End Class
If you don't know how many labels there are, one option is to use a Do Loop.
Dim lblTarget As Label = Nothing
Dim intCursor As Integer = 1
Dim bolFirstIteration As Boolean = True
Do Until lblTarget Is Nothing AndAlso Not bolFirstIteration
If bolFirstIteration Then
bolFirstIteration = False
End If
lblTarget = CType(Me.Controls("lbl_" & intCursor.ToString()), Label)
If Not lblTarget Is Nothing Then
lblTarget.Text = (intCursor * 2).ToString()
End If
intCursor += 1
Loop
Related
I am trying to go through un-checked items within a CheckedListBox1 and based on the values returned hide relevant columns within DataGridView1 but the issue is that the values displayed in CheckedListBox1 are the HeaderText property of DGV column and not the Name property which is required for hiding the column within DGV.
See below code:
For Each checked_item As Object In CheckedListBox1.Items
If Not CheckedListBox1.CheckedItems.Contains(checked_item) Then
DataGridView1.Columns("").Visible = False
End If
Next
Is there a way to retrieve "Name" property of DGV column when referencing the column's HeaderText property?
You don't need the column name to hide the column. You need the column. The name is just a means to get the column. The issue is the way you're populating your CheckedListBox. Displaying the HeaderText makes perfect sense, because that's what the user actually sees. What you should be doing is putting the columns themselves into the CheckedListBox and just displaying the HeaderText. That way, the items are the columns, e.g.
Dim columns = DataGridView1.Columns.Cast(Of DataGridViewColumn)().ToArray()
With CheckedListBox1
.DataSource = columns
.DisplayMember = NameOf(DataGridViewColumn.HeaderText)
End With
The code you posted then becomes this:
For i = 0 To CheckedListBox1.Items.Count - 1
Dim column = DirectCast(CheckedListBox1.Items(i), DataGridViewColumn)
column.Visible = CheckedListBox1.GetItemChecked(i)
Next
Note that you should generally set the DataSource last when binding but that doesn't seem to work with a CheckedListBox, which doesn't offically support data-binding. For that reason, the DataSource is set first.
EDIT:
I'm adding this after the comment was added to the question about the ItemCheck event and the checking of the items at startup. The key here is to not actually act on the event until the list has been initialised, i.e. all the items have been initially checked. One way to do that would be like so:
Private isLoaded As Boolean = False
Private Sub Form1_Load(...) Handles MyBase.Load
'Bind the data and check the items in the CheckedListBox here.
isLoaded = True
End Sub
Private Sub CheckedListBox1_ItemCheck(...) CheckedListBox1.ItemCheck
If isLoaded Then
'Act here.
End If
End Sub
The other way to is to prevent event being raised by not handling it while the initialisation is taking place. That can be done in a couple of ways but I'll leave that to you as an exercise if that's what you want to do.
As the ItemCheck event is raised before the state of an item changes, you will need to treat the current item differently to the other items. My loop above would become this:
For i = 0 To CheckedListBox1.Items.Count - 1
Dim column = DirectCast(CheckedListBox1.Items(i), DataGridViewColumn)
'For the item that is being checked/unchecked, use its new state.
'For other items, use their current state.
column.Visible = If(i = e.Index,
e.NewValue = CheckState.Checked,
CheckedListBox1.GetItemChecked(i))
Next
That said, if all items are initially checked and all columns are initially visible, it's only the current item that you need to care about, so there's no need for a loop at all:
Dim column = DirectCast(CheckedListBox1.Items(e.Index), DataGridViewColumn)
column.Visible = (e.NewValue = CheckState.Checked)
Try this:
For Each checked_item As Object In CheckedListBox1.Items
Dim oCol As DataGridViewColumn = DataGridView1.Columns _
.Cast(Of DataGridViewColumn)() _
.Where(Function(x) x.HeaderText = checked_item).SingleOrDefault()
If oCol IsNot Nothing Then oCol.Visible = _
Not CheckedListBox1.CheckedItems.Contains(checked_item)
Next
Note: System.Linq is required!
[EDIT]
this code is executed in the .ItemCheck event. When the form starts up
I loop through all available columns, populate CheckedBoxList1 and as
default they are un-checked but I want them checked as I want the
columns to be visible at start
If you would like to change the visibility of column of currently selected item in CheckListBox (in ItemCheck event), use this:
Dim oCol As DataGridViewColumn = DataGridView1.Columns _
.Cast(Of DataGridViewColumn)() _
.Where(Function(x) x.HeaderText = checked_item).SingleOrDefault()
If oCol IsNot Nothing Then oCol.Visible = _
Not CheckedListBox1.CheckedItems.Contains(CheckedListBox1.SelectedItem)
Do you see the difference?
The main difference is: there's no foreach loop ;)
Right now I have many locations with this structure. At the moment I have: name as string and x,y,z positions as single. So it's a mix of data types and I might want to add both more data in the future and also other data types. I must be able to easily extract any part of this data.
Example of how I'll work with this data is: When I choose South Wales from a combobox then I want to get its properties, x,y,z populated in a textbox. So they need to be "linked". If I choose London then it'll have its x,y,z properties etc.
My initial idea is just to dim every single data such as in the first example below. This should be the easiest way with 100% control of what's what, and I could easily extract any single data but at the same time might get tedious I assume, or am I wrong? Is it a good way to approach this?
Dim SW_FP As String = "South Wales"
Dim SW_FP_X As Single = "489,1154"
Dim SW_FP_Y As Single = "-8836,795"
Dim SW_FP_Z As Single = "109,6124"
The next example below is something i just googled up. Is this a good method?
Dim dt As DataTable = New DataTable
dt.Columns.Add("South Wales", GetType(String))
dt.Columns.Add("489,1154", GetType(Single))
dt.Columns.Add("-8836,795", GetType(Single))
dt.Columns.Add("109,6124", GetType(Single))
OR should I use something else? Arrays, Objects with properties... and this is where my ideas end. Are there other methods? XML?
I want to do it in a smart way from start instead of risking to rewrite/recreate everything in the future. So my main question is: Which method would you suggest to be the smartest to choose? and also if you could provide a super tiny code example.
You mentioned that when you choose an item you want to get it's properties. This shows that you are looking for objects. If not using a database one example could be to make Location objects and have a List of these to be added or removed from. Then you have a lot of different ways to get the data back from the List. For example:
Class:
Public Class Location
Public Property Name As String
Public Property X As Single
Public Property Y As Single
Public Property Z As Single
End Class
List:
Dim locations As New List(Of Location)
Dim location As New Location With {
.Name = "South Wales",
.X = 1.1,
.Y = 1.2,
.Z = 1.3
}
locations.Add(location)
LINQ to get result:
Dim result = locations.SingleOrDefault(Function(i) i.Name = "South Wales")
This is just an example for use within your program, hope it helps.
Disclaimer: Untested code. It's more to guide you than copy-paste into your project.
First, create a Class that will represent the structured data:
Public Class Location
Public Property Name As String
Public Property PositionX As Single
Public Property PositionY As Single
Public Property PositionZ As Single
Public Sub New()
Me.New (String.Empty, 0, 0, 0)
End Sub
Public Sub New(name As String, x As Single, y As Single, z As Single)
Me.Name = name
Me.PositionX = x
Me.PositionY = y
Me.PositionZ = z
End Sub
Now, you can create a List(Of Location) and use that List to bind to a ComboBox, like this:
Dim list As New List(Of Location) = someOtherClass.ReadLocations ' Returns a List(Of Location) from your database, or file, or whatever.
cboLocations.DataSource = list
cboLocations.DisplayMember = "Name" ' The name of the Location class' Property to display.
cboLocations.ValueMember = "Name" ' Use the same Name Property since you have no ID.
You can also forego the list variable declaration like the following, but I wanted to show the declaration of list above:
cboLocations.DataSource = someOtherClass.ReadLocations
Function someOtherClass.ReadLocations() may populate the List(Of Locations) in a way similar to this. Note I'm not including data access code; this is just an example to show how to add Location objects to the List(Of Location):
Dim list As List(Of Location)
' Some loop construct
For each foo in Bar
Dim item As New Location(foo.Name, foo.X, foo.Y, foo.Z)
list.Add(item)
' End loop
Return list
The "magic" happens when you select an option from the ComboBox. I forget the ComboBox event offhand, so that's homework for you :-) You take the selected Object of the ComboBox and cast it back to the native type, in this case Location:
Dim item As Location = DirectCast(cboLocations.SelectedItem, Location)
txtName.Text = item.Name
txtPosX.Text = item.PositionX.ToString
txtPosY.Text = item.PositionY.ToString
txtPosZ.Text = item.PositionZ.ToString
Here is one way, using a DataTable as you mentioned. This is a stand alone example project just to show code used.
This example loads data from file is found and saves data on exit.
Form1 Image
' Stand alone example
' needs DataGridView1, Label1 and
' ComboBox1 on the Designer
' copy/replace this code with default
Option Strict On
Option Explicit On
Public Class Form1
Dim dt As New DataTable("Freddy")
Dim bs As New BindingSource
'edit path/filename to use as test data path
Dim filepath As String = "C:\Users\lesha\Desktop\TestData.xml"
Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
dt.WriteXml(filepath)
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
With dt
dt.Columns.Add("Country", GetType(String))
dt.Columns.Add("x", GetType(String))
dt.Columns.Add("y", GetType(String))
dt.Columns.Add("z", GetType(String))
' add extra column to hold concatenated
' location (could be a hidden column)
dt.Columns.Add("CombLoc", GetType(String), "'x = ' + x + ' y = ' + y + ' z = ' + z")
If IO.File.Exists(filepath) Then
' saved file found so load it
dt.ReadXml(filepath)
Else
' no saved file so make one test row
.Rows.Add("South Wales", 489.1154, -8836.795, 109.6124)
End If
End With
bs.DataSource = dt
DataGridView1.DataSource = bs
' set any properties for DataGridView1
With DataGridView1
' to hide Combined Location column
.Columns("CombLoc").Visible = False
' dontwant row headers
.RowHeadersVisible = False
End With
set up ComboBox
With ComboBox1
.DataSource = bs
' displayed item
.DisplayMember = "Country"
' returned item
.ValueMember = "CombLoc"
If .Items.Count > 0 Then .SelectedIndex = 0
End With
' default Label text
Label1.Text = "No items found"
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
no items in list so exit sub
If ComboBox1.SelectedIndex < 0 Then Exit Sub
send returneditem to Label
Label1.Text = ComboBox1.SelectedValue.ToString
End Sub
End Class
Si I'm working on an assignment where I have 10 RadioButtons indicating how many contesters I have, and depending on what I pick between 1 to 10, I need that many of my corresponding TextBoxes to be enabled so I could fill it with names!
Is there a way for me to make a For loop between 1 and the number I picked from the RadioButton and say something like
For i = 0 to Size
{
TextBox&i.Enabled = True
}
Since my TextBoxs are called TextBox1 to TextBox10
I know you can add strings together using &, but how can I do that for an object name?
As of right now I literally have the dumbest way of doing it, which is a click event inside each RadioButton that manually enables the correct number of TextBoxes...
Thank you in advance!
You can iterate over all controls like this:
For Each ctr In Me.Controls
Dim indx As String = ctr.Name
If TypeOf (ctr) Is Textbox Then
' Now compare the name with TextBox&i and do smth
End If
Next
It's not possible to just concatenate a string and use it as an object variable reference like that, but you can search the form's controls by their name property (which is a string) and do it that way. Here's an example:
Private Sub EnableTextBoxes(ByVal Size As Integer)
For i As Integer = 1 To Size
Dim matches() As Control = Me.Controls.Find("Textbox" & i.ToString, True)
If matches IsNot Nothing AndAlso matches.Length = 1 Then matches(0).Enabled = True
Next
End Sub
I would like to know if you can use one general if statement for the same condition but on multiple controls?
for example, If I have five labels and I want each label to say "hello" when I push a button I would write something like
If Label1.Text = "" Then
Label1.Text = "hello"
End If
But instead of writing an if statement for each label is there a way to apply this one if statement to all five labels?
Yes, you can iterate over all controls in a form, but you'd need to restrict them to Label instances, fortunately LINQ makes this easy:
Dim emptyLabels As IEnumerable(Of Label) = _
Me.Controls.OfType(Of Label)().Where(Function(l) l.Text.Length = 0)
For Each label As Label In emptyLabels
label.Text = "hello"
Next
You could do this:
Dim ifEmptyAssignHello As Action(Of Label) = _
Sub(l)
If l.Text = "" Then
l.Text = "Hello"
End If
End Sub
ifEmptyAssignHello(Label1)
ifEmptyAssignHello(Label2)
ifEmptyAssignHello(Label3)
Well you could
make a method which takes a label,
then pass labels into it.
Public Sub SayHello(l As Label)
If (l is Nothing) Then Return
If (l.Text = "") Then
l.Text = "Hello"
End If
End Sub
...
For Each l As Label in anyLabels
SayHello(l)
End For
The most concise way to do what you describe is to iterate over an explicit array of the labels. VB.Net will notice that they're all Labels and figure out the type for you.
For Each individualLabel In {Label1,
Label2,
Label3,
Label4,
Label5}
If individualLabel.Text = "" Then individualLabel.Text = "hello"
Next
Of course, if you need to do this more than once, you'll want to define a variable to refer to that particular group of five labels.
Dim myFiveLabels As IEnumerable(Of Label) = {Label1, Label2, Label3, Label4, Label5}
(We explicitly define the variable as an IEnumerable because this way it can only be used to iterate over each element of the group. If it were defined as an Array or List, you could e.g. add / remove elements and generally complicate its behaviour.)
I have a problem with the auto-complete behaviour of comboboxes in VB.NET (with the .NET framework 2.0).
I am using a combobox to type in numeric values, and its DropDown list to suggest possible numeric values. This list is sorted in ascending order, for example {"10","92", "9000", "9001"}.
The combobox properties are set as follow:
AutoCompleteMode: SuggestAppend
AutoCompleteSource: ListItems
DropDownStyle: DropDown
Sorted: False
The DropDown list is simply filled like this:
myCombobox.Items.Add("10")
myCombobox.Items.Add("92")
myCombobox.Items.Add("9000")
myCombobox.Items.Add("9001")
When I don't type anything, the order of values of the DropDown list is correct, in original/ascending order. However, when I start typing something, the suggested values in the DropDown list get sorted (alphanumerically): if I type "9", the list of suggestions becomes {"9000", "9001", "92"}.
I would like to prevent this behaviour to get the values of the list in the original/ascending order. I can't figure out how...
A possible work-around would be to pad with zeroes the values in the list, e.g. {"0010", "0092", "9000", "9001"} but I would like to avoid this.
Edit:
As suggested by bendataclear, one can use a list box to display the suggestions.
This will work for small lists but doesn't scale well to large lists. It may be useful for some applications. Based on the code given by bendataclear, I made it work this way:
Private Sub ComboBox1_KeyUp(sender As System.Object, e As System.Windows.Forms.KeyEventArgs) Handles ComboBox1.KeyUp
Dim cursorPos As Integer = ComboBox1.SelectionStart
ListBox1.Items.Clear()
For Each s In ComboBox1.Items
If s.StartsWith(ComboBox1.Text) Then
ListBox1.Items.Add(s)
End If
Next
If ListBox1.Items.Count > 0 And ComboBox1.Text.Length > 0 Then
ComboBox1.Text = ListBox1.Items(0)
ComboBox1.SelectionStart = cursorPos
ComboBox1.SelectionLength = 0
End If
End Sub
The code has not been thoroughly tested and can be improved, but the main idea is there.
Edit 2:
Using DataGridView leads to better performance; it was sufficient for me. Thanks bendataclear.
Just out of curiosity, any other answer is welcomed :)
Seems to be an issue when the combo box displays the data, as even if you set a custom source it re-orders alphabetically:
ComboBox1.Items.Add("10")
ComboBox1.Items.Add("92")
ComboBox1.Items.Add("9000")
ComboBox1.Items.Add("9001")
ComboBox1.AutoCompleteCustomSource.Add("10")
ComboBox1.AutoCompleteCustomSource.Add("92")
ComboBox1.AutoCompleteCustomSource.Add("9000")
ComboBox1.AutoCompleteCustomSource.Add("9001")
ComboBox1.AutoCompleteSource = AutoCompleteSource.CustomSource
I think the only way I can think of is to create your own autocomplete something like (untested):
Dim cbotxt As String = ComboBox1.Text
Dim key As String
key = ChrW(e.KeyCode)
ListBox1.Items.Clear()
For Each i In ComboBox1.Items
Dim s As String = i.ToString()
If s.StartsWith(ComboBox1.Text & key) Then
ListBox1.Items.Add(s)
End If
Next
If ListBox1.Items.Count > 0 Then
ListBox1.Visible = True
ComboBox1.Text = ListBox1.Items(0)
End If
Edit:
A good approach for many items (I'm using for 10000+ in an application):
First change from a list box to a datagridview.
Then declare a list of strings and fill with values you want to autocomplete
Dim Numberlist as List<Of String>
' Fill List using Numberlist.Add("String")
Then in the text change property:
Filter = NumberList.FindAll(AddressOf checkNum)
DataGridView1.DataSource = Filter
And add the function to check the strings.
Function checkNum(ByVal b As String) As Boolean
If b.StartsWith(ComboBox1.Text) Then
Return True
Else
Return False
End If
End Function
This method runs on my machine with 10k items faster than I can type.