VB.net MVC understanding and binding - vb.net

Question

I am trying to seperate my code logic from my gui as in MVC principles, what I am trying to achieve is quite simple I believe
I have my Form1, which contains a textbox and button, once the button is clicked it loads a function in my controller class which adds a string to a database using entity and then should update the textbox with this name.
I thought what I would need to do is pass the original form through and then databind to the textbox object on the form, this is where I have come unstuck though, as my logic fails...
Public Class Form1
Private mf As New MainForm(Me)
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
mf.buttonClick()
End Sub
End Class
Public Class MainForm
Private Property a As Form
Public Sub New(ByVal s As Form)
a = s
End Sub
Function buttonClick() As Boolean
Dim context As TestDBEntities2 = New TestDBEntities2
Dim newCategory As tTable = New tTable
newCategory.Name = "Test1 " & Today.DayOfWeek
context.tTables.Add(newCategory)
context.SaveChanges()
Dim current As String = newCategory.Name
a.DataBindings.Add("text", "TextBox1", current)
Return True
End Function
End Class
and my error:
Cannot bind to the property or column Test1 6 on the DataSource.
Am I looking at this the right way? Or am I so far off that there is an obvious reason this doesn't work?
Any input would be appreciated! Whats the best way to pass data back to a source without returning it in as a result of a function?

Answer 1

You should consider changing your code a bit, so that it reflects more the MVC structure:
use Events to exchange data and indicate action triggers, instead of using the form object
normally the controller has knowledge of the form and not the other way around, so swap this in your project. This reflects also the first point
So a possible solution for a Windows Forms application could look like this:
The form that has one button and one text field, one event to signal the button click and one WriteOnly property to fill the TextBox from outside the form:
Public Class MainForm
Public Event GenerateAndShowEvent()
' allow text box filling
Public WriteOnly Property SetTextBoxContent()
Set(ByVal value)
generatedInputTextBox.Text = value
End Set
End Property
Private Sub generateAndShowButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles generateAndShowButton.Click
' forward message: inform the subscriber that something happened
RaiseEvent GenerateAndShowEvent()
End Sub
End Class
The controller class has knowledge of the form, creates it, binds (listens) to the form's button click event and makes the form ReadOnly for the world (exposes the form):
Public Class MainFormController
' the form that the controller manages
Private dialog As MainForm = Nothing
Public Sub New()
dialog = New MainForm()
' bind to the form button click event in order to generate the text and response
AddHandler dialog.GenerateAndShowEvent, AddressOf Me.GenerateAndShowText
End Sub
' allow the world to access readonly the form - used to start the application
Public ReadOnly Property GetMainForm()
Get
Return dialog
End Get
End Property
Private Sub GenerateAndShowText()
' create the text
Dim text As String = "Test test test"
' access the Database ...
' give the generated text to the UI = MainForm dialog!
dialog.SetTextBoxContent = text
End Sub
End Class
Now what left is to create first the controller, that creates the form and use the form to show it. This can be done like this:
Create an AppStarter module with a Main method:
Module AppStarter
Sub Main()
Application.EnableVisualStyles()
Application.SetCompatibleTextRenderingDefault(False)
' create the controller object
Dim controller As MainFormController = New MainFormController()
' use the public property to get the dialog
Application.Run(controller.GetMainForm)
End Sub
End Module
In your project settings uncheck the enable application framework setting and set the AppStarter module as the start point of your project:
Now you have a Windows Form Project using the MVC pattern.
If you still want to use DataBinding for the TextBox control, then create a Data Transfer Object or DTO that represents the fields you will transfer from your controller to the form:
Public Class DataContainer
Private t As String
Private i As Integer
Public Property Text() As String
Get
Return t
End Get
Set(ByVal value As String)
t = value
End Set
End Property
Public Property Id() As Integer
Get
Return i
End Get
Set(ByVal value As Integer)
i = value
End Set
End Property
End Class
Then add a BindingSource for your TextBox and configure it to use the DTObject:
Now bind the TextBox control to the DataBinding control:
What left is to add a public setter for the TextBox data binding control in the form:
Public Property TextBoxDataSource()
Get
Return TextBoxBindingSource.DataSource
End Get
Set(ByVal value)
TextBoxBindingSource.DataSource = value
End Set
End Property
and transfer the data from the controller:
Private Sub GenerateAndShowText()
' create the text
Dim text As String = "Test test test"
' access the Database ...
' give the generated text to the UI = MainForm dialog!
'dialog.SetTextBoxContent = text
Dim data As DataContainer = New DataContainer
data.Text = text
data.Id = 1 ' not used currently
dialog.TextBoxDataSource = data
End Sub
The binding can also be set programmatically - instead of doing this over the control property window, add the following code in the constructor of the form:
Public Sub New()
InitializeComponent()
' bind the TextBox control manually to the binding source
' first Text is the TextBox.Text property
' last Text is the DataContainer.Text property
generatedInputTextBox.DataBindings.Add(New Binding("Text", TextBoxBindingSource, "Text"))
End Sub

Answer 2

You seem to misunderstand the Add method.
The first argument is the name of the control's property to which you are binding. This should be "Text", not "text".
The second argument is an object that contains the data you want to bind. You have passed the name of the target control, rather than the source of the data. You are also binding to the form rather than the text box. So what you have said is that you want to bind the form's text property to data that can be extracted from the string "TextBox1".
The third argument says where to go to find the data. For example, if you passed a FileInfo object for the second argument, and you wanted to bind the file's path, you would pass the string "FullName", because that is the name of the property containing the data you want. So you have told the binding to look for a property on the string class called "Test1 6", which is why you have received the error message saying it can't be found.
I think what you want is
a.TextBox1.DataBindings.Add("Text", newCategory, "Name");