I have a variable whose scope needs to be global, because it needs to be called in a function as well as in a button press. So I declared the variable in a Module so it would be global.
The problem is that the value of this variable needs to be equal to the value of the text property of a textbox in the form.
Here you can download the VB.net demonstration of my problem: http://db.tt/DDxQJDXl
Below is an explanation of what happens
You enter a string into the textbox, in this case I entered "Hello". Then you click the button and it displays what you wrote.
You click OK in that message box and change the value in the textbox. In this case I changed it to "Goodbye". Then I hit the button again, but the variable did not change values and the messagebox displays "Hello" again.
Here is the entire source code:
Module Module1
Public strDataValue = frmTest.txtDataValue.Text
End Module
Public Class frmTest
Private Sub btnTest_Click(sender As System.Object, e As System.EventArgs) Handles btnTest.Click
MsgBox(strDataValue)
End Sub
End Class
Note: This is just a demonstration of a problem I'm having in a much larger program so the variable does have to be global.
You need to set the value of the field to the new value in the TextBox:
Private Sub btnTest_Click(sender As System.Object, e As System.EventArgs) Handles btnTest.Click
strDataValue = txtDataValue.Text
MsgBox(strDataValue)
End Sub
The field will not change values by itself.
The value of strDataValue won't automatically change when txtDataValue.Text changes. You need to update strDataValue manually, either when the textbox loses focus, or when you click the Test button.
You could also have a public property, which automatically returns the actual value as long as the form is open.
Public ReadOnly Property DataValue() As String
Get
Return frmTest.txtDataValue.Text
End Get
End Property
You need to assign value of txtDataValue.Text to your variable strDataValue in better performance
Using of Timer object or TextChenged event not recommended
Any change of txtDataValue.Text can assign after end of editing action
for me best solution: Leave or LostFocus events
Private Sub txtDataValue_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtDataValue.Leave
strDataValue = txtDataValue.Text
End Sub
Related
I'm building a form that has many buttons, all buttons do the same thing: add 1 every time they are clicked. Every pressed button is sent to a datagridview along with the time they are pressed. Datagrid values look like this:
a_1_serv (button name), 18:05:00(time).
Sometimes I want to delete the last row. Everything works fine so far.
When I delete the last row, I want to change the text of the button (a_1_serv).
I can parse the dgv value (a_1_serv) to a variable but I can't bind it to the appropriate button name so I can control it.
Is there a way to do it?
Don't store your program state in your UI
Create a data structure to hold the information, and let the DataGridView be a "view", not treating it as a variable. You will save yourself headaches vs using the UI as a variable.
That said, create a class to represent your information
Public Class Data
Public Sub New(button As Button, time As DateTime)
Me.Button = button
Me.Time = time
End Sub
<System.ComponentModel.Browsable(False)>
Public Property Button As Button
Public ReadOnly Property Text As String
Get
Return Button.Name
End Get
End Property
Public Property Time As DateTime
End Class
And your code can manipulate the data in a variable off the UI. Bind the data to the DataGridView for display.
Private datas As New List(Of Data)()
Private Sub Button_Click(sender As Object, e As EventArgs) Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click
addButton(DirectCast(sender, Button))
End Sub
Private Sub RemoveLastButton_Click(sender As Object, e As EventArgs) Handles RemoveLastButton.Click
removeLast()
End Sub
Private Sub addButton(b As Button)
datas.Add(New Data(b, DateTime.Now))
bindData()
End Sub
Private Sub removeLast()
Dim b = datas.Last.Button
b.Text = "new text" ' change to whatever
datas.RemoveAt(datas.Count - 1)
bindData()
End Sub
Private Sub bindData()
DataGridView1.DataSource = Nothing
DataGridView1.DataSource = datas
End Sub
This does exactly what you stated but there may be inconsistency in these two bits of information you provided: a_1_serv (button name) and I want to change the text of the button .... This changes the button text but not the name. The name is displayed in the grid. You can change the data class to display the text or whatever. But the point is this approach will keep your data off the UI and you won't need to look up the control by name anymore.
I have a Window-Form 'caller' in vb.net containing a datagridview with a small overview table of certain objects, each with its own ID in the first column. Now, if a row is double clicked, i want to show a dialog 'edit', where one can edit many details of that row which i do not want in the overview table.
My approach is as follows: In the caller form i wrote this to call 'edit':
Private Sub dgdata_dbclick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellMouseEventArgs) Handles dg_data.CellMouseDoubleClick
Dim f_edit As New edit
f_edit.ShowDialog(Me)
End Sub
That works fine.
However, in the called Form "edit" i need to check, which ID was selected and load this data from the database to edit it. I can access some data from the calling form 'caller' using e.g.
MsgBox(CType(Me.Owner, caller).Text)
to show the window title of 'caller'. However, i want to extract the currently selected ID in the datagridview or at least some variabhle containing it. In the caller form, this could be easily done by evaluating
dg_data.Item(0, selectedRow).Value.ToString
but i cannot access any relevant information in 'caller'. I have a public class with some global variables there but i cannot access them as well.
Probably my strategy to solve this problem is not the most clever approach? Basically, i want to open a very detailed edit window when someone clicks on a line in an overviewtable but simultaniously blocking the rest of the application as long as the edit window is open.
Thanks!
The idea is to pass the data to the second form. When you create an instance of the second form (my class is called Form2, yours is called edit) with the New keyword the Sub New is called on Form2.
Private Sub OpenEditDialog()
Dim f_edit As New Form2(32) '32 is the number you retrieve from your DataGridView
f_edit.ShowDialog(Me)
f_edit.Dispose()
End Sub
You pass the ID to Form2 and set a variable at Form level. You can then use the variable anywhere in Form2.
Public Class Form2
Private ID As Long
Public Sub New(SelectedID As Long)
InitializeComponent()
ID = SelectedID
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
MessageBox.Show(ID.ToString)
End Sub
End Class
You need to call InitializeComponent() so the controls will show up.
How do you usually get data into objects? You set a property or pass an argument to a method or constructor? Why should this be any different? Decide which you want to use and then write that code in your form. If it's required data, I would suggest a constructor. Just write this code in your form:
Public Sub New
and hit Enter. That will generate a little extra code automatically. You can then add a field to store the value, a parameter to the constructor and then assign the parameter to the field inside.
Thank you for pointing me to the correct route.
I solved it like this (which works fine and which is hopefully acceptable):
In the calling form:
Private Sub dgdata_dbclick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellMouseEventArgs) Handles dg_data.CellMouseDoubleClick
Dim selectedRow As Integer = dg_data.CurrentCell.RowIndex
Dim f_edit As New edit
f_edit.edit(dg_data.Item(0, selectedRow).Value.ToString)
f_edit.ShowDialog(Me)
f_edit.Dispose()
End Sub
In the called form:
Public Sub edit(ByVal id As Long) 'Handles MyBase.Load
'Enter commands to prepare your form
End Sub
I have a spelling application that I am building in VB.Net, where I have a textbox receiving simple input (spelling words), and a label which will show the output. What I want to accomplish is when I enter something in the textbox, I can see it in my label - as I am typing into the textbox.
I will admit that I don't know what I'm doing, as I've never tried this before, so I don't know to begin in terms of setting up what I need to do. I know that I'll need some variable to hold my String input, and will probably need some type of loop, but beyond that, I am lost. The only other example is in C#, and doesn't help me any.
Can anyone give me a simple model to work off of, so I can put the approach into memory? For now, all I have is code stub from my TextChanged event handler:
Private Sub txtSpell_TextChanged(sender As Object, e As EventArgs) Handles txtSpell.TextChanged
'Set variables to hold values.
Dim someText As String
'Connect the label and textbox.
lblShowInput.Text = txtWordInput.Text
'Process loop to populate the label from textbox input.
for '(This is where I am lost on the approach)
End Sub
I know that I'll need some variable to hold my String input, and will
probably need some type of loop
I don't think you'll need a loop, or the variable to hold the value. You almost have it:
Private Sub txtSpell_TextChanged(sender As Object, e As EventArgs) Handles txtSpell.TextChanged
'Connect the label and textbox.
lblShowInput.Text = txtSpell.Text
End Sub
In the code you provided, you are referencing an object named txtWordInput inside your txtSpell text changed event handler. If you are entering the text in the txtWordInput input, you'll want to handle this in the txtWordInput textChanged event handler:
Private Sub txtWordInput_TextChanged(sender As Object, e As EventArgs) Handles txtWordInput.TextChanged
'Connect the label and textbox.
lblShowInput.Text = txtWordInput.Text
End Sub
Follow-up:
The TextChanged event is the correct event for this.
In your code, you are assigning lblShowInput.Text to txtWordInput.Text, but in the txtSpell TextChanged event handler.
You want to be in the TextChanged event handler for whatever TextBox you would like to use to update the label, as the text is changing.
To give a better example, I have created a simple Winforms VB application that has only a textbox named InputTextBox and a label named Output Label.
The Form:
The Code:
Public Class Form1
Private Sub InputTextBox_TextChanged(sender As System.Object, e As System.EventArgs) Handles InputTextBox.TextChanged
OutputLabel.Text = InputTextBox.Text
End Sub
End Class
Explanation:
InputTextBox_TextChanged is the method name generated by Visual Studio for our event handler
Handles InputTextBox.TextChanged ties the method to an actual event it is handling.
When the InputTextBox text property is changed (typically by user input), whatever we have in our InputTextBox_TextChanged Sub will execute. In this case, I am assigning the Text of OutputLabel to the Text of the InputTextBox
Output:
Resources:
I've uploaded this simple demo to GitHub if you'd like a closer look.
Take a look at the TextChanged documentation
I have a class A which contains 2 user controls declared as
Friend WithEvents CustInfo1 As WindowsApplication1.CustInfo
Friend WithEvents ServiceLocation1 As WindowsApplication1.ServiceLocation
Both have textBoxes. If value of textBoxA in custInfo1 changes then how can I make value of textBoxB in SeviceLocation1 also change
I will be most thankful if anyone can help me.
Thanks
You need to do the following:
Inside the CustInfo user control, you need to write code inside the textBoxA Changed event that raises an event from the CustInfo user control (e.g. TextBoxChanged event). RaiseEvent statement
Inside the ServiceLocation user control, create a public property getter and setter for whatever your textBoxB.Text is
On the form that contains both user controls, create code in the new CustInfo TextBoxChanged event and set the new property on the ServiceLocation1 user control.
All controls (also custom controls) have the property Controls, through which you can access the (sub) controls of that control. Now you can retrieve your textbox by calling the .Item(key) method on it. Then you can assign a event handler to it in your form or class.
Dim key As String = "textBoxA" 'Or simply the name of that TextBox in your CustInfo
Dim textboxA As TextBox = CustInfo1.Controls.Item(key)
AddHandler textBoxA.TextChanged, AddressOf mytextchangedhandler
Where that mytextchangedhandler handles the TextChanged event for that TextBox.
Personally I don't like this method too much, as you are relying on knowing either the name of the TextBox or the index in the Controls list of your usercontrol.
I would definitely go for the option to create your own event on your usercontrol. It is quite easy to do even! Below how to do it. In the code behind of your usercontrol, you'll have to add an event declaration:
Event MyTextBoxChanged(sender As Object, e As EventArgs)
Now we'll have to raise it, we do this by implementing the TextChanged event of the TextBoxA in your usercontrol (as you explained you wanted to do):
Private Sub TextBoxA_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBoxA.TextChanged
RaiseEvent MyTextBoxChanged(Me, EventArgs.Empty)
End Sub
Now we can simply implement this event (MyTextBoxChanged) in your Form as follows:
Private Sub CustInfo1_MyTextBoxChanged(sender As System.Object, e As System.EventArgs) Handles CustInfo1.MyTextBoxChanged
' Do something
End Sub
Obviously we still need to get the updated text, now we can create our own EventArgs that will give us the new (and/or old value) as you will want to have. We simply can inherit the System.EventArgs class and add some properties (for example a property OldText that holds the old text value and a property NewText that holds the new text value):
Public Class MyEventArgs
Inherits System.EventArgs
Private _OldText As String
Public ReadOnly Property OldText() As String
Get
Return _OldText
End Get
End Property
Private _NewText As String
Public ReadOnly Property NewText() As String
Get
Return _NewText
End Get
End Property
Public Sub New(oldText As String, newText As String)
_OldText = oldText
_NewText = newText
End Sub
End Class
Now we have to change the event definition and raising to use the MyEventArgs:
Event MyTextBoxChanged(sender As Object, e As MyEventArgs)
Private Sub TextBoxA_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBoxA.TextChanged
RaiseEvent MyTextBoxChanged(Me, New MyEventArgs(TextBoxA.Text))
End Sub
And also change the implementation in your Form:
Private Sub CustInfo1_MyTextBoxChanged(sender As System.Object, e As MyEventArgs) Handles CustInfo1.MyTextBoxChanged
MessageBox.Show(e.Text)
End Sub
More information about events can be found on our favorite spot MSDN.
I have a mdicontainer form that summons forms. My problem is when the a user clicks again the menu for that form, it also make another instance of it.
What I did is declare a public class with a public variable on it ex: Boolean isFormOneOpen = false. Then every time formOne opens, it checks first the global variable I declared a while ago if it's false, if it is, instantiate an object of a formOne and then show it. Otherwise, do nothing. Very static, imagine if I have many forms, I have to declare a variable for each form to check if it's already open. Can you provide me a solution for this? Maybe a method that accepts a Form? Or any more clever way to do this.
You don't need a variable, you could iterate the MdiChildren collection to see if the form is already opened. For example:
Private Sub btnViewChild_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnViewChild.Click
For Each child In Me.MdiChildren
If TypeOf child Is Form2 Then
child.WindowState = FormWindowState.Normal
child.Focus()
Exit sub
End If
Next
Dim frm As New Form2
frm.MdiParent = Me
frm.Show()
End Sub
The VB.NET-centric solution:
Private Sub btnViewChild_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnViewChild.Click
Form2.MdiParent = Me
Form2.WindowState = FormWindowState.Normal
Form2.Show
End Sub
Rather than a boolean, declare a variable of the form's type. Then just make sure the variable isn't Nothing and call it's .Open() method. This has the nice side effect of also bringing your existing form instance to the front if it's already open.
Even better, in VB.Net 2.0 and later all forms have a default instance with the same name as their type, so you can just say FormName.Open() and be done with it. However, I haven't tried this in an mdi situation before.