Public Class Form1
Private Sub btnAddCat_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAddCat.Click
If txtAdd.Text <> "" Then
comboBox1.Items.Add(txtAdd.Text)
txtAdd.Clear()
Else
MessageBox.Show("Fill the blanket")
End If
End Sub
End Class
If user close application should see the items but there is no items
Can anyone help?
thanks
If you want the application to remember the value the next time it is run, you will need to save the value to disk. There are many different options for how to do that (e.g. text file, XML, database, registry), but for simple tasks, I'd recommend just using the built-in Settings feature.
To use the Settings feature, first you need to open your project properties screen. Then select the Settings tab. Add a new setting by typing in the name and selecting a data type. For instance, you could type MyItems for the name, and then select System.Collections.Specialized.StringCollection as the data type. Then, in your code, you can read the current value of the setting like this (perhaps in your form's Load event handler):
For Each i As String In My.Settings.MyItems
ComboBox1.Items.Add(i)
Next
And then you could save the list to the setting, like this (perhaps in your form's FormClosed event handler):
My.Settings.MyItems.Clear()
For Each i As String In ComboBox1.Items
My.Settings.MyItems.Add(i)
Next
You need to persist the data to a data store (either the database or the file system) so that the next time the application runs, then it can check the data store and display the items to the user.
Related
I don't normally post on forums because I try to find information for myself, and ask as an absolute last resort. I've tried scouring the net for answers, but I'm only receiving about half of the answer I'm looking for.
I'm currently building an application that deals with state law. There's one combo box and one text box. One for the offense title, and one for the numerical code for that particular code section. So say if I select "Kidnapping", it prepopulates the text box below it with "11-5-77", for example.
The method I've been using for, oh, about the last hour now, is:
If AWOffenseTitle.Text = "Kidnapping" Then
AWCN.Text = "11-5-77"
ElseIf AWOffenseTitle.Text = "False Imprisonment" Then
AWCN.Text = "11-5-78"
With AWOffenseTitle being the combo box name, and AWCN being the text box name. While this has proved to work perfectly well so far, I'm sure you can imagine with hundreds of offense titles, this is going to take a ridiculously long time. Well, I finally found a spreadsheet with offense titles and their respective title codes. What I'm looking to do is create two text files within a folder in the local directory "Offenses". One with a vertical list of offenses, and one with a vertical list of offense code numbers that populate the same lines in each. What I'm looking to do is populate the combo box with the contents of text file one (which I can do already), but then selecting an offense title will read the second text file and display it's proper title code. That's what has me at a loss. I'm relatively well-versed with vb.NET, but I'm not an expert by any means.
I'm hoping someone here will be able to provide a code example and explain it to me line-by-line so I can gain a better understanding. I want to get more proficient with VB although it's not so popular anymore. I've been using VB since 6.0, but not on a regular basis. More on a sporadic project kind of basis.
I really appreciate any assistance anyone might be able to provide, and if you need more information, I'd be glad to answer any questions. I tried to be as thorough as I could.
Thank you in advance!
First, you need to retrieve your data. I demonstrated using an Sql Server database containing a table named Offenses with columns named OffenseTitle and OffenseCode. You will have to change this code to match your situation.
Private Function GetOffenseData() As DataTable
Dim dt As New DataTable
Using cn As New SqlConnection("Your connection string"),
cmd As New SqlCommand("Select OffenseTitle, OffenseCode From Offenses;")
cn.Open()
dt.Load(cmd.ExecuteReader)
End Using
Return dt
End Function
As the Form loads, set the properties of the ComboBox. DisplayMember matches the name of the title column and ValueMember is the name of the code column.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim dt = GetOffenseData()
ComboBox1.DisplayMember = "OffenseTitle"
ComboBox1.ValueMember = "OffenseCode"
ComboBox1.DataSource = dt
End Sub
Then when the selected item in the combo changes, just set the .Text property of TextBox to the SelectedValue in the combo and your code appears.
Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
TextBox1.Text = ComboBox1.SelectedValue.ToString
End Sub
There are other ways to do this if your data source is other than a database. Please advise if you need additional help.
In addition to HardCode's comment and Mary's detailed answer, I can only add an answer that's somewhere in between them.
It might be the case, that the information is not taken from a database, but from another source, like a text/data file or a web service. So it might be useful to create an abstraction for the data source you actually use.
First, I create a class or struct that will hold the data for each combo box item.
Class Offense
Public ReadOnly Property Title As String
Public ReadOnly Property Code As String
Public Sub New(title As String, code As String)
Me.Title = title
Me.Code = code
End Sub
End Class
Next, you need a method that retrieves a list of offenses that you can bind to your combo box. It's entirely up to you how you fill/fetch the offenses list. I have simply hard coded your two values here.
Private Function GetOffenseData() As List(Of Offense)
Dim offenses As New List(Of Offense)
offenses.Add(New Offense("Kidnapping", "11-5-77"))
offenses.Add(New Offense("False Imprisonment", "11-5-78"))
Return offenses
End Function
At a certain moment (probably in your form's Load event handler), you need to initialize your combo box. Just like Mary did, I use data binding.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
AWOffenseTitle.DropDownStyle = ComboBoxStyle.DropDownList
AWCN.ReadOnly = True
AWOffenseTitle.DisplayMember = NameOf(Offense.Title)
AWOffenseTitle.ValueMember = NameOf(Offense.Code)
AWOffenseTitle.DataSource = GetOffenseData()
End Sub
Note that I use the NameOf operator to get the desired property names of the Offense class. If you ever decide to rename the properties of your Offense class, you will be able to easily detect where they are used, since the compiler will complain if your code still uses the wrong property names somewhere.
Finally, the app needs to react to combo box value changes, so that the text box will show the corresponding offense code. Mary used an event handler for the SelectionChangeCommitted event, but I use a handler for the SelectedIndexChanged event instead:
Private Sub AWOffenseTitle_SelectedIndexChanged(sender As Object, e As EventArgs) Handles AWOffenseTitle.SelectedIndexChanged
AWCN.Text = AWOffenseTitle.SelectedValue
End Sub
(Up to now, I was not aware of the SelectionChangeCommitted event of the ComboBox control. I will need to look into this event to see if it is actually a better choice for this scenario, but I found that the SelectedIndexChanged event does the job just fine, so for now I sticked with that event, since I am more familiar with it.)
Hi i'm new in programming world and I've started my programming by Visual BASIC. I'm trying to set a value of a variable through the program closing event and load the same value in program load event. As example:
At first I tried:
Dim Age as Integer
Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
Age = 50
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Textbox1.text = Age
End Sub
But when I close the program and restart it, it resets to zero.
Next I tried "Settings" from properties but if I move my program from one location to another then it also resets everything.
Finally I tried Stream readers and writers to catch the final value but for this I had to attach some text files to the programs which I don't want. Can anyone help me how to solve the following problem with custom class libraries or by something else?
All the variables that you have are run time variables. What that means is it will only have value till your program is running.
If you want to store the data taken from user, you store it in database. You can use any kind of database and connect it to your program, store everything in there. You can also retrieve the values from database to use in system when you restart your program.
If you are new to programming and trying to learn visual basic, start with basic concepts or pick up a book that start with basics. Once you know the basics of programming, you can read about connecting program to database.
The value of age is never going to remain static when the application is shut down unless you keep it in the application settings or some sort of flat file, database etc. The initial value could be set in the application when the form opens or from at static value in application settings, but unless you store the value somewhere other than memory, it will not persist.
What you can do is create a form called module1.vb . in this form declare and set your variables . . .
Example
Public Age As Integer = 50
On my form I have a menu with "file-save". When I click save I want to save particular settings to restore when the form is closed and re-opened. I've done this successfully for text in text-boxes and the checked states of check-boxes, but I'm failing when trying to loop through the items in a list-box. Please see below for what I've tried...
When I click save:
Private Sub SaveToolStripMenuItem_Click(sender As Object, e As EventArgs)
Handles SaveToolStripMenuItem.Click
For Each i In ListBox1.Items()
My.Settings.ListBox1.Add(i)
Next
My.Settings.Save()
End Sub
When my form loads:
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Handles Me.Load
For Each i In My.Settings.ListBox1()
ListBox1.Items.Add(i)
Next
End Sub
I've only been using VB for three days, so apologies if I am missing something simple ha! Thanks for any help!!!
There is one small glitch with the StringCollection in settings. If you do not seed it with a fake variable then it starts out as Nothing and you cannot add to Nothing. in your form load add this:
' if the collection has not been initialized, do so
If My.Settings.ListBox1 Is Nothing Then
My.Settings.ListBox1= New System.Collections.Specialized.StringCollection
End If
' now it is safe to use: load strings from Setting -> form listbox
For Each s As String In My.Settings.ListBox1()
ListBox1.Items.Add(s)
Next
The very first time it runs, there are likely no saved settings, so we have to create the container for them, basically.
Option Strict can be implemented by file, by adding this at the top:
Option Strict On
Or for the project: Project => Properties => Compile: Option Strict is likely to the right (I have 2012). You can also set it as a permanent option (recommended).
Among other things, this will prevent you from plucking variables out of the air and use them without declaring a type (which will lead to errors). For instance:
For Each i In My.Settings.ListBox1()
becomes
For Each s As String In My.Settings.ListBox1() ' tell the compiler the Type
I need a little advice in manipulating DataGridView in Visual Basic .Net. This is my first time playing with DataGridView. My program is to load a .txt file containing data of every room in a building and display them in the DataGridView.
Here is a portion of the file showing 2 rooms:
1;1812;1812;F18;T1;26808.16;.00;.00;.00;.00;.00;.00;
1;1813;1813;F18;T1;24000.00;3500.00;.00;300.00;.00;.00;.00
A room is a one-line string that ends with an endline character.
I have no problem with loading the file and getting all these information. I store data of each room into an object of class Room, and put them in a list.
Right now, I put all of the properties of the room into the data grid's columns like this:
Now, how can I put all these rooms' data into the grid? I tried follow http://www.dotnetperls.com/datagridview-vbnet at first, but setting DataSource to a list of class Room imitating from the given link doesn't show anything in the grid view. How can we tell the program to link rows of the grid to a list of objects? Or am I doing it wrong?
So any advise is appreciated. How do we do this?
I think you'll be pleasantly surprised at how easy this is to do with BindingSources and Visual Studio.
Create your Room Class (already done I presume)
Build your project
Set your Class as your DGV's DataSource:
Click the DGV's smart tag (or the DataSource field in the DGV's property sheet) and on the 'Choose Data Source' pulldown select 'Add Project Data Source...'
On the 'Data Source Config Wizard' select Object and click Next
Navigate your assembly's class structure to select the Class you created in step 1 and click Next
Click Finish to close the Wizard
You'll notice that a new BindingSource has been added to your project. You'll use this BindingSource to bind your List of Room objects to your DGV. Your code will look something like this after you fill your List of Rooms:
roomBindingSource.DataSource = roomList
Note that you'll start with a DataGridView with no columns. After you follow the steps above your DGV will be populated with columns based on the accessibility of the fields in the class you're binding to. At this point you can customize the appearance of the columns such as including removing/adding, etc.
Your problem is that you are using the designer to create your columns and then not linking the DataSource properties to these columns.
The link you posted is talking about automatically generating columns based upon the DataSource which is a list of objects, in that link they do not create the columns in the designer, but instead rely upon the AutoGenerateColumns property being set to true for the DataGridView.
There is a forum post here which talks about what you need to do. It is also described quite well on MSDN.
Basically you need to set the DataPropertyName for each column to match the desired property from your object.
So if your object looks like:
class Room
{
public string RoomName() {get; set;}
}
You need to set the DataPropertyName property to RoomName for the room name column in the grid designer.
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
' Uses Test class from above.
Dim list = New List(Of Test)
list.Add(New Test("Mac", 2200))
list.Add(New Test("PC", 1100))
DataGridView1.DataSource = list
End Sub
Private Sub DataGridView1_SelectionChanged(ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles DataGridView1.SelectionChanged
' Get the current cell location.
Dim y As Integer = DataGridView1.CurrentCellAddress.Y
Dim x As Integer = DataGridView1.CurrentCellAddress.X
' Write coordinates to console.
Console.WriteLine(y.ToString + " " + x.ToString)
End Sub
End Class
is it possible to have specific text in a listbox line to act like a hyperlink?
dim sLocation as string = "\\server\folder\subfolder\"
LstOut.Items.Add("text text text" & sLocation)
I would like this to open in explorer.
This is not an ASP application, just a plain old winform.
I googled you question and on Tek-Tips Forums it says:
I would create a datatable that
contains the hyperlink text, and the
actualy HREF. catch the onclick event
of the list box, grab the record they
clicked, and use
system.diagnostics.process.start(HREF)
to open the default browser to the
link.
One suggestion would be to monitor when the listbox's index is changed. When it's changed, check to see if the index you're looking at is the one that ultimately needs to open up explorer. You could use a process.start command to open up explorer. I'm thinking something along the lines of
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
if (listBox1.selectedIndex = indexToLookFor) Then
Process.start("explorer.exe", File_Path)
End If
End sub
Now, if you wanted to have the text from the selected item act as a local link to another folder on the system, it would simply be a matter of using this call instead
process.start("explorer.exe", listbox1.text)