I created a registration form and added a form with features "Update, Delete, Refresh," along with a DataGridView to show data from the registration form.
Here's my form:
Since I inserted a TreeView, when I click the Update button as in the picture, I get the error:
Object Reference Not set to an instance of an object
I think my code in the TreeView form is wrong.
This is what I entered:
Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterSelect
If e.Node.Text = "Update/Delete Student" Then
Dim regstu As New Registered_Students
regstu.MdiParent = Me
regstu.Show()
End If
End Sub
Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterSelect
If e.Node.Text = "Update/Delete Student" Then
Dim regstu As New Registered_Students
Form_father.IsMdiContainer = True
Form_father.TopLevel = False
regstu.MdiParent = New Form_father
Form_father.Panel1_Container.Controls.Add(regstu)
regstu.Show()
End If
End Sub
Related
Here is my code, everytime I click the Button1, instead of refreshing the Datagridview, it only adds another entry that is a duplicate of the previous one. I know I'm missing something in my code that will clear the data in Datagrid before loading it again. Please help..
Private Function LoadData_UnitProcess()
Dim UP_SQL As String = "SELECT LotNum FROM Transactions WHERE StatusID=3 ORDER BY Process_EntryDate DESC"
Dim UP_Ad As OleDbDataAdapter = New OleDbDataAdapter(UP_SQL, strCon)
UP_Ad.Fill(UP_Ds, "Transactions")
UnitOnProcess_DG.DataSource = UP_Ds.Tables(0)
With UnitOnProcess_DG
.RowHeadersVisible = False
.Columns(0).HeaderCell.Value = "Lot #"
.Columns(0).Width = "363"
.AllowUserToAddRows = False
End With
LoadData_UnitProcess = ""
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
LoadData_UnitProcess()
End Sub
Private Sub Displayer_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
LoadData_UnitProcess()
End Sub
You dataset UP_Ds is probably a property or field. You need to reset the dataset before filling it again, otherwise the content is appended to the previous.
UP_Ds.Reset()
UP_Ad.Fill(UP_Ds, "Transactions")
UnitOnProcess_DG.DataSource = UP_Ds.Tables(0)
I need to write this small program in visual basic, but i face a problem which is i can't change the color or add list form text file during runtime.
this is picture of what i wont to do
http://i62.tinypic.com/30tghh0.png
And this is the code i wrote so far,,
Public Class Form1
Private Sub NewToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewToolStripMenuItem.Click
Dim listBox1 As New System.Windows.Forms.ListBox
listBox1.Text = "New List"
listBox1.Location = New Point(25, 25)
listBox1.Size = New Size(380, 280)
Me.Controls.Add(listBox1)
OpenToolStripMenuItem.Enabled = True
SaveToolStripMenuItem.Enabled = True
SaveAsToolStripMenuItem.Enabled = True
CloseToolStripMenuItem.Enabled = True
EditToolStripMenuItem.Enabled = True
End Sub
Private Sub ExirToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExirToolStripMenuItem.Click
End
End Sub
Private Sub OpenToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OpenToolStripMenuItem.Click
If (OpenFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK) Then
Dim myfile As String = OpenFileDialog1.FileName
Dim allLines As String() = File.ReadAllLines(myfile)
For Each line As String In allLines
ListBox1.Items.Add(line)
Next
End If
End Sub
End Class
The problem as you see is in OpenToolStripMenuItem sub with line ListBox1.Items.Add(line)
is there is no listbox1 because is not created yet.the same with color, save and the rest.
so, please help me to solve it.
Move the declaration of ListBox1 out to the Class level:
Public Class Form1
Private ListBox1 As System.Windows.Forms.ListBox
Private Sub NewToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewToolStripMenuItem.Click
ListBox1 = New System.Windows.Forms.ListBox
...
End Sub
...
End Class
*But why create it at run-time like this? You could add it at design-time and set the Visible() property to False. When the New button is clicked, you change Visible() to True. Unless you need a new ListBox to be created each time so you have more than one? If so, how will they be laid out?...
I am working on windows form application and I have two forms. 1 is visitorinfo 2 is vistorexitsign.
In the visitorinfo I have save button, while cliking save button I want to get textboxvalue from vistirexitsign form.
Both forms are running at the same time, I have given code like this in save button of visitor info form:
Private Sub BtnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSave.Click
Dim obj As New VisitorExitsign
Dim vs As String = obj.txtvisitoridExit.Text
Dim Visitorid As String = My.Forms.VisitorExitsign.txtvisitoridExit.Text
But I am always getting here txtvisitoridexit.text value null. Not getting the text value.
What is wrong with my code?
You are creating new instance in every click event.
Dim obj As New VisitorExitsign
So the values are set in the new objects but not in existing object.
So actually you have to refer to existing object of VisitorExitsign.
EDIT:
For example:
You are creating form VisitorExitsign in some method.
So whenever you are creating store its reference in some global variable.
VisitorExitsign obj = new VisitorExitsign
at the place where you are creating form
then in click event use obj and assign text.
When you refer to My.Forms.VisitorExitSign.txtvisitoridExit.Text you are referencing the form itself rather than an instance of the form, if that makes sense. So, you are trying to access the default form rather than one which the user has entered text into.
What you probably want to do is to change
Dim Visitorid As String = My.Forms.VisitorExitsign.txtvisitoridExit.Text`
into
Dim Visitorid As String = obj.txtvisitoridExit.Text
What that will do is make sure that the Visitorid is getting it's value from an instance of VisitorExitSign.
Try Like This
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Handles Button1.Click
Dim forms As FormCollection = Application.OpenForms
For Each form As Form In forms
If form.Name = "VisitorExitsign" Then
Dim vs As String = CType(form, VisitorExitsign).txtvisitoridExit.Text
End If
Next
End Sub
Suggesstion:
frmVX = New VisitorExitsign
frmVX.Location = New Point(781, 0)
frmVX.MdiParent = Me
frmVX.Show()
frmVE = New VisitorInfo()
frmVE.Location = New Point(0, 0)
frmVE.MdiParent = Me
frmVE.Tag=frmVX
frmVE.Show()
Button_Click Event
Dim vs As String = CType(me.Tag, VisitorExitsign).txtvisitoridExit.Text
Hope this will works
create a module
Module modTextValue
Public _textVal As String
End Module
then goto txtvisitoridexit's LostFocus event on your form vistirexitsign
Private Sub txtvisitoridexit_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.LostFocus
_textVal = txtvisitoridexit.Text
End Sub
on btnSave'click
Private Sub BtnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSave.Click
Dim str As String
str = _textVal
End Sub
Try this :
in button save update your code to :
Private Sub BtnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSave.Click
Dim obj As New VisitorExitsign
obj.ShowDialog()
Dim vs As String = obj.txtvisitoridExit.Text
End sub
when you close VisitorExitsign, the variable vs will take the value of obj.txtvisitoridExit
I have a ListBox (LB) with a DataTable (DT) DataSource in the Form Class globally populated in the Form_Load event.
Private Sub frmEditPresets_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
DT.Columns.Add("DisplayText")
DT.Columns.Add("PresetID")
For Each TSI As ToolStripItem In Presets.DropDownItems
If TSI.Name.IndexOf("preset_") > -1 Then
DT.Rows.Add(TSI.Text, TSI.Name)
End If
Next
LB.DataSource = DT
LB.DisplayMember = "DisplayText"
End Sub
When I use my Rename button. It updates the menu item and the Data Source but the Listbox doesn't refresh until I click another item in the listbox.
Rename code:
Private Sub btnRename_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRename.Click
Dim R As DataRowView = LB.SelectedItem
Dim S As String = InputBox("Preset Name", "Rename", R("DisplayText"))
If S.Trim.Length = 0 Then Exit Sub
If Presets.DropDownItems.ContainsKey(R("PresetID").ToString) Then
Presets.DropDownItems(R("PresetID").ToString).Text = S
End If
R("DisplayText") = S
End Sub
I'm sure this is a simple question with a simple answer but I can't seem to figure it out. I've tried Refresh(). I've tried setting the DataSource again. I read this StackOverflow question Winforms listbox not updating when bound data changes but ResetBindings() doesn't seem to be an available method in this context.
*Edit. I gave Steve credit for the answer as he mentioned BindingContext. Although, that led me to find BindingContext(DT).EndCurrentEdit() which updated my LB display and maintained the selection.
Tried with this, and it works.....
Private Sub btnRename_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRename.Click
Dim R As DataRowView = LB.SelectedItem
Dim S As String = InputBox("Preset Name", "Rename", R("DisplayText"))
If S.Trim.Length = 0 Then Exit Sub
If Presets.DropDownItems.ContainsKey(R("PresetID").ToString) Then
Presets.DropDownItems(R("PresetID").ToString).Text = S
End If
R("DisplayText") = S
BindingContext(DT).EndCurrentEdit()
End Sub
Using VB.Net (Windows Application)
In the form (called as FirstForm), i am using textbox, add-form Button, search button.
When i click the add-form button, it will give the new form (same as FirstForm)
Code for adding new form
Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click
Dim SecondForm As New FirstForm
SecondForm.Show()
End Sub
Search Button Code
Private Sub Search_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Search.Click
If FirstForm.Focus = True Then
FirstForm.textbox1.Text = gridview1.Rows(crRow).Cells("code").Value.ToString().Trim()
Else
Dim SecondForm As New FirstForm
SecondForm.textbox1.Text = gridview1.Rows(crRow).Cells("code").Value.ToString().Trim()
End If
End Sub
The above code is working, but If i am in second Form when i click the search button and selected the value, then the value is appearing in the FirstForm textbox, it is not appearing in the SecondForm textbox.
If SecondForm is showing, the selected Value should appear in the SecondForm textbox not in the FirstForm Textbox.
How to solve this issue.
Need Vb.net code Help
Use Me - Reference variable which hold ref. of current form.
Dim frm As FirstForm
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
If IsNothing(frm) OrElse frm.IsDisposed Then
frm = New FirstForm
End If
frm.Show()
End Sub
Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
Me.textbox1.Text = gridview1.Rows(crRow).Cells("code").Value.ToString().Trim()
End Sub
Using "me" will not solve the problem?? why are you referring to the form in a static way?
Private Sub Search_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Search.Click
textbox1.Text = gridview1.Rows(crRow).Cells("code").Value.ToString().Trim()
End Sub