Let's say I want to set the property of every item in a list like this:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim test As New List(Of PictureBox)
For q = 1 To 25
Dim picbox As New PictureBox
test.Add(picbox)
Next
timer tick
test.Item(everything in list).Top -= 3
End Sub
Can I do it all at once instead of iterating and setting each value separately?
You should just update the color before adding it to your list:
For q = 1 To 25
picBox.BackColor = Color.AliceBlue
test.Add(picbox)
Next
As an aside, do you realize that you are adding the same item 25 times? If you want different instances you'd need to create a new one in your loop:
For q = 1 To 25
picBox = New PictureBox
picBox.BackColor = Color.AliceBlue
test.Add(picbox)
Next
Just for fun, you could rewrite your entire snippet like so to get a list of 25 PictureBoxes:
Dim test = Enumerable.Range(1,25) _
.Select(Function(i) New PictureBox With {.BackColor = Color.AliceBlue}) _
.ToList
Related
I was trying to remove this "brickn" when ball intersect with this brick
but i am facing problem that "brickn" is not declared any helps?
there is code
Dim brickWidth as Integer = 0
Public Function CreateBrick() As PictureBox
Dim Brickn As New PictureBox
Me.Controls.Add(Brickn)
Brickn.Size = Brick.Size
Brickn.Left = BrickWidth
Brickn.Top = 0
Brickn.Image = Brick.Image
Brickn.SizeMode = PictureBoxSizeMode.StretchImage
Brickn.BackColor = Color.Black
Return Brickn
End Function
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
For i= -75 To Me.Width
CreateBrick()
BrickWidth += 170 ' increasing brick.left on every new brick is created
i += 170 ' increasing looop count according to brick needed
Next
Private Sub Boll_control_Tick(sender As Object, e As EventArgs) Handles Boll_control.Tick
If Ball.Bounds.IntersectsWith(brickn.Bounds) Then
Me.Controls.Remove(brickn)
End If
End Sub
why this "brickn" is not saying not declared in "boll control tick " timer
You are instantiating brickn withing CreateBrick. You are returning it as the result of that function, but not assigning it to anything. So it's scope is limited to the CreateBrick fuction only, which is why it's not accessible from Boll_control_Tick.
Also you are then trying to create multiple instances of it with using a single object.
This code will allow you to create one or more. You will then need to rework your Boll_control_Tick to work out whether it intersects with any. You may want to create a list or array of PictureBox objects as Brickn instead of one.
Dim brickWidth as Integer = 0
Dim Brickn As PictureBox ' This may be better as a list or an array
Public Function CreateBrick() As PictureBox
Dim myBrickn As New PictureBox
'Note - no idea what Brick is here or where it comes from
Brickn.Size = Brick.Size
Brickn.Left = BrickWidth
Brickn.Top = 0
Brickn.Image = Brick.Image
Brickn.SizeMode = PictureBoxSizeMode.StretchImage
Brickn.BackColor = Color.Black
Return myBrickn
End Function
and then in your Form_Load method:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
For i= -75 To Me.Width
Brickn = CreateBrick() ' or add to your List/Array here
Me.Controls.Add(Brickn)
BrickWidth += 170 ' increasing brick.left on every new brick is created
i += 170 ' increasing looop count according to brick needed
Next
That will add multiple picture boxes to your controls and, if you want, create a list or array of them for easy access. You will need to loop through those in Boll_control_Tick to see if ball bounds intersects with any and then remove that specific one only
I am trying to take Items that I have already added to a list.
Dim lista As New List(Of String)
n = 2
i = 0
Do While i < n + 1
Randomize()
a = Int(Rnd() * 4) + 1
If a = 1 Then
lista.Add("1b")
ElseIf a = 2 Then
lista.Add("2b")
ElseIf a = 3 Then
lista.Add("3b")
ElseIf a = 4 Then
lista.Add("4b")
End If
i = i + 1
Loop
Lets imagine that the list i got was {2b,4b,1b}. Now i want to know how to get lets say just 2b from the list as a first Item and then delete it from the list.
This would be a good place to use a Queue(Of ).
Dim item As String
item = queuea.Dequeue
But List(Of ) has an indexer so you can just use it like an array:
Dim item As String
item = lista(0)
' Then remove the first item:
lista.RemoveAt(0)
Use the .net Random class instead of the old VB6 methods. Calling Random.Next(Interger1, Integer2) will return an Integer equal to or greater than Integer1 and less than Integer2. Note that since the values are so limited there is a good chance of having duplicates in the list.
Although multiple ElseIfs will work, a Select Case is easier to read and less typing.
I put the contents of the list in a ListBox so we could see what was going on. I used the Remove method of List(Of T) then rebind the ListBox.
Private lista As New BindingList(Of String)
Private rand As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BuildList()
ListBox1.DataSource = lista
End Sub
Private Sub BuildList()
Dim i = 0
Dim a As Integer
Do While i < 3 'since n never changes just use the literal value
a = rand.Next(1, 5)
Select Case a
Case 1
lista.Add("1b")
Case 2
lista.Add("2b")
Case 3
lista.Add("3b")
Case 4
lista.Add("4b")
End Select
i = i + 1
Loop
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 'Remove from list
lista.Remove(ListBox1.SelectedItem.ToString)
End Sub
I have a program that regularly updates a few datagridviews with new data that is received via TCP. The problem I am having is that the screen refresh is quite slow. Bellow is a stripped back version of my code. This example takes 1.1s to update the screen each time the loop in StartButton_Click is iterated. How can I make this faster without reducing the amount of data that is shown?
I added a stopwatch to try and work out what lines of code were causing the biggest issue. From the tests, it seemed that the main issue was updating the datagridview cells with a new number.
I'm not sure how to make this faster as my program relies on the values being updated regularly. Is a datagridview not the right object for this application? Should i be using something else? Is there a way to get a datagridview to update faster?
Public Class Form1
Public DataTable1 As New DataTable
Private Sub Load_From(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
DataGridView1.DataSource = DataTable1
Me.Height = 700
Me.Width = 1000
DataGridView1.Location = New Point(10, 10)
DataGridView1.Width = Me.Width - 10
DataGridView1.Height = Me.Height - 10
For c As Integer = 0 To 20
DataTable1.Columns.Add("col" & c)
If DataTable1.Rows.Count = 0 Then
DataTable1.Rows.Add()
End If
DataGridView1.Columns(c).AutoSizeMode = DataGridViewAutoSizeColumnMode.None '0%
DataTable1.Rows(0).Item(c) = "col" & c
DataGridView1.Columns(c).Width = 40
'Header
DataGridView1.Rows(0).Cells(c).Style.Alignment = DataGridViewContentAlignment.MiddleCenter
DataGridView1.Rows(0).Cells(c).Style.WrapMode = DataGridViewTriState.True
DataGridView1.Rows(0).Cells(c).Style.Font = New Font("Verdana", 8, FontStyle.Bold)
'Data
DataGridView1.Columns(c).DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight
DataGridView1.Columns(c).DefaultCellStyle.WrapMode = DataGridViewTriState.False
DataGridView1.Columns(c).DefaultCellStyle.Font = New Font("Verdana", 8, FontStyle.Regular)
Next
For r As Integer = 1 To 25
DataTable1.Rows.Add()
Next
End Sub
Private Sub StartButton_Click(sender As Object, e As EventArgs) Handles StartButton.Click
Dim stpw As New Stopwatch
stpw.Reset()
stpw.Start()
For i As Integer = 0 To 10
Dim rand As New Random
Dim randnumber As Double = rand.Next(5, 15) / 10
UpdateDataTable(randnumber)
DataGridView1.Update()
Me.Text = i & "/100"
Next
stpw.Stop()
MsgBox(stpw.Elapsed.TotalMilliseconds)
End Sub
Private Sub UpdateDataTable(ByVal offset As Double)
For r As Integer = 1 To DataTable1.Rows.Count - 1 'loop through rows
For c As Integer = 0 To DataTable1.Columns.Count - 1 '89%
DataTable1.Rows(r).Item(c) = (r / c) * offset
Next
Next
End Sub
End Class
Edit:
I have to admit that I totally botched my original answer by erroneously believing that the call to DataGridView.Update was not needed to emulate the OP conditions. I am leaving my original text as it may be of use for someone in another situation.
A potential solution is to use a DoubleBuffered DataGridView. This can be accomplished by creating a class that inherits from DataGridView and enables DoubleBuffering.
Public Class BufferedDataGridView : Inherits DataGridView
Public Sub New()
MyBase.New()
Me.DoubleBuffered = True
End Sub
Protected Overrides Sub OnPaint(e As PaintEventArgs)
e.Graphics.Clear(Me.BackgroundColor)
MyBase.OnPaint(e)
End Sub
End Class
Doing this yields a change in appearance in that the client area is black until something is drawn on it. To alleviate this, the class overrides the OnPaint method to draw a background.
In my testing this reduced the bench-march time from approximately 2600 ms to approximately 600 ms.
End Edit
In addition to the highly pertinent suggestions of #Visual Vincent in the comments regarding eliminating unnecessary updating, I would recommend that you use a BindingSource to encapsulate the DataTable and use that as the DataGridview.DataSource.
Private bs As New BindingSource
Private Sub Load_From(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
bs.DataSource = DataTable1
DataGridView1.DataSource = bs
This will allow you to temporary suspend change events raised through the DataTable that cause the DataGridView to repaint cells.
Private Sub UpdateDataTable(ByVal offset As Double)
' prevent each item change from raising an event that causes a redraw
bs.RaiseListChangedEvents = False
For r As Integer = 1 To DataTable1.Rows.Count - 1 'loop through rows
For c As Integer = 0 To DataTable1.Columns.Count - 1 '89%
DataTable1.Rows(r).Item(c) = (r / c) * offset
Next
Next
bs.RaiseListChangedEvents = True ' re-enable change events
bs.ResetBindings(False) ' Force bound controls to re-read list
End Sub
This way the will only repaint once to reflect all the changes to the underlying DataTable.
I wan't to create a bunch of variables inside a While, each one with different names.
Here is what i tried:
Dim asd As Integer = 1
While asd < 5
Dim picturebox +asd As New Picturebox
End While
I want that it creates the Picturebox1 Picturebox2 ... and so on, but the "asd" variable won't evaluate and the code won't work. How could you create variables with different names in a loop with Visual Studio?
What I've done in the past is something like:
For i = 0 to 5
Dim t As New PictureBox()
t.Name = "PictureBox" & i
Me.Controls.Add(t)
Next
Dim picToChange = From r in Me.Controls Where Typeof(r) Is PictureBox AndAlso r.Name = "PictureBox1" Select r
If picToChange IsNot Nothing AndAlso picToChange.Any Then
'Do Something
End If
This is a very basic example and your linq would probably be more dynamic than the one I used but you should get the idea. In this case I'm assuming that you are just putting the PictureBoxes on the form, if this isn't the case then you will need to linq through whichever collection you are adding the controls to.
Edit #1:
As far as events are concerned you will need to add the handlers manually. So your code would become:
For i = 0 to 5
Dim t As New PictureBox()
t.Name = "PictureBox" & i
AddHandler t.Click, AddressOf(FunctionToHandleClick)
Me.Controls.Add(t)
Next
Dim picToChange = From r in Me.Controls Where Typeof(r) Is PictureBox AndAlso r.Name = "PictureBox1" Select r
If picToChange IsNot Nothing AndAlso picToChange.Any Then
'Do Something
End If
And the FunctionToHandleClick would look like this:
Private Sub FunctionToHandleClick(ByVal sender As Object, ByVal e As ClickEventArgs)
End Sub
Why don't you use an Array?
Dim pictureboxes(5) As PictureBox
For i As Integer = 0 To 5
pictureboxes(i) = New PictureBox()
Next
I have 2 text files named sQue.txt containing single words in each lines (each word in each line) and sObj.txt also containing single word in each line (but no. of entries are more in this file than in sQue.txt).
Now, I have a blank form in which I want to read both the above files & display them in a manner such that:
Each entry from sQue.txt file gets displayed in separate labels in the form
All the entries of file sObj.txt are put in a CheckedListBox & this CheckedListBox appears for each label displayed in point 1. above.
Example:
sObj.txt contains 3 entries aaa, bbb & ccc (vertically i.e each in new line).
sQue.txt contains 5 entries p,q,r,s & t (vertically i.e each in new line).
Now, when the form loads, 3 labels are seen with texts aaa, bbb & ccc. Also 3 CheckedListBoxes are seen containg p,q,r,s & t in each box.
Can it be done? I'm trying to find a solution with no luck yet.
Please help.
Till now all I have is
Private Sub Form7_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim queue As String() = IO.File.ReadAllLines("C:\temp\sQue.txt")
Dim objects As String() = IO.File.ReadAllLines("C:\temp\sObj.txt")
For i = 0 To queue.Count - 1
'create labels here
For j=0 to objects.Count - 1
'create CheckedListBoxes
Next
Next
End Sub
If you use a groupbox you can use the text property as your label, and add a checkedlistbox to the groupbox with the items you want. This code will do that:
Imports System.IO
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Dim NewForm2 As New Form2
NewForm2.Show()
Dim sObj() As String = File.ReadAllLines("sobj.txt")
Dim sQue() As String = File.ReadAllLines("sQue.txt")
For Each s As String In sObj
Me.Controls.Add(MakeNewGB(s, sQue))
Next
End Sub
End Class
Public Module Module1
Friend WithEvents NewGB As System.Windows.Forms.GroupBox
Friend WithEvents NewCLB As System.Windows.Forms.CheckedListBox
Public NextColumn As Integer = 0
Public Function MakeNewGB(lbl As String, clbItems() As String) As GroupBox
NewGB = New System.Windows.Forms.GroupBox()
NewCLB = New System.Windows.Forms.CheckedListBox()
NewGB.SuspendLayout()
'GroupBox1
'
NewGB.Controls.Add(NewCLB)
NewGB.Location = New System.Drawing.Point(NextColumn, 0)
NewGB.Name = lbl
NewGB.Size = New System.Drawing.Size(126, 210)
NewGB.TabIndex = 0
NewGB.TabStop = False
NewGB.Text = lbl
'
'CheckedListBox1
'
NewCLB.FormattingEnabled = True
NewCLB.Location = New System.Drawing.Point(6, 19)
NewCLB.Name = "clb" + lbl
NewCLB.Size = New System.Drawing.Size(103, 184)
NewCLB.TabIndex = 0
NewCLB.Items.AddRange(clbItems)
NextColumn += NewGB.Size.Width + 10
Return NewGB
End Function
End Module
I think your code should look like this. But i am not sure what the purpose of it is.
Private Sub Form7_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim queue As String() = IO.File.ReadAllLines("C:\temp\sQue.txt")
Dim objects As String() = IO.File.ReadAllLines("C:\temp\sObj.txt")
For i = 0 To queue.Count - 1
'create labels here
Dim label as new Label
label.Text = queue(i)
Dim chklst as new CheckedListBox
For j=0 to objects.Count - 1
'create CheckedListBoxes
chklst.Items.Add(object(j))
Next
Me.Controls.Add(label)
Me.Controls.Add(chklst)
Next
End Sub