I'm try to improve our dynamic reporting system. I would like to add event handle to the object I've dynamically created on the form. One of the functions of this would be to populate a listbox from what was selected in the first listbox. i.e. The user select a town and the second listbox is populated by all the people living in that town.
The objectaction and objectactionfunction would be stored in a SQL table in the system. I would also like to store the objectactionfunction code in the table and dynamically create it at runtime. I've been looking into CodeDOM. Am I looking in the right direction.
Pseudocode below
dim objectaction as string
dim objectactionfunction as string
objectaction = "LostFocus"
objectactionfunction =" "
addHandler textbox1.objectaction, addressof objectactionfunction
Here is an example of using Reflection to register an event handler using Strings to specify the event name and the event handler name:
Imports System.Reflection
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim eventName = "Leave"
Dim methodName = "TextBox1_Leave"
Dim targetType = TextBox1.GetType()
Dim [event] = targetType.GetEvent(eventName)
Dim eventHandlerType = [event].EventHandlerType
Dim eventHandlerMethod = Me.GetType().GetMethod(methodName, BindingFlags.NonPublic Or BindingFlags.Instance)
Dim eventHandlerDelegate = eventHandlerMethod.CreateDelegate(eventHandlerType, Me)
[event].AddEventHandler(TextBox1, eventHandlerDelegate)
End Sub
Private Sub TextBox1_Leave(sender As Object, e As EventArgs)
MessageBox.Show("Success!")
End Sub
End Class
As I said in my comment, the code is rather verbose but that's the way it goes. Here's an extension method that you can use to write code once and use it wherever you like:
Imports System.Reflection
Imports System.Runtime.CompilerServices
Public Module ObjectExtensions
<Extension>
Public Sub AddEventHandler(source As Object,
eventName As String,
eventHandlerName As String,
eventHandlerSource As Object)
Dim [event] = source.GetType().GetEvent(eventName)
Dim eventHandlerMethod = eventHandlerSource.GetType().GetMethod(eventHandlerName, BindingFlags.NonPublic Or BindingFlags.Instance)
Dim eventHandlerDelegate = eventHandlerMethod.CreateDelegate([event].EventHandlerType, eventHandlerSource)
[event].AddEventHandler(source, eventHandlerDelegate)
End Sub
End Module
Sample usage:
Dim eventName = "Leave"
Dim methodName = "TextBox1_Leave"
TextBox1.AddEventHandler(eventName, methodName, Me)
Related
Basically, I am rewriting some code working for years. Over the time I have many (60+) references to forms - there's a menuitem with OnClick event for each form, where a form reference was created:
Private Sub SomeForm_Click(sender As Object, e As EventArgs) Handles MenuItemForSomeForm.Click
NewTab("Some Form", New SomeForm, 0)
End Sub
...where first parameter is a name to put in a tabPage.Text where the form is opened, second is a new instance of the (particular) form SomeForm and 0 is a default record to display (0 means no default record).
Now, I created a dynamic menu and stored the form names in a database (due to better access control over the access rights, etc). Now, because the menu is generated at runtime, I can't have the OnClick event with separate instance definition of the form and have to create it at runtime, after the MenuItems are created. The side-effect idea was to cut the code short by using only 1 OnClick event or such with MenuItem.Tag paremeter as FormName. Something like:
Private Sub clickeventhandler(sender As Object, e As EventArgs)
Dim tsmi As ToolStripMenuItem = CType(sender, ToolStripMenuItem)
Dim newForm As New >>>FormFrom(tsmi.Tag.ToString)<<< ' only explanation, this won't work
MainW.OpenModuleInTab(new newForm, tsmi.Tag.ToString, 0)
However I am failing to find a way to create form (instances) from this string reference. Reference through collection (i.e. List(of) or Dictionary) would be fine too, I believe.
The structure is obviously:
Object → Form → Form1 (class) → MyForm1 (instance)
I know I can create an object like this:
' Note that you are getting a NEW instance of MyClassA
Dim MyInstance As Object = Activator.CreateInstance(Type.GetType(NameOfMyClass))
I can re-type it to a Form type:
Dim NewForm as Form = CType(MyInstance,Form)
... to acccess some of the form properties like Width, TopLevel, etc., but that's about it. I can't do:
Dim NewForm1 as Form1 = CType(NewForm,Form1)
...because obviously, Form1 comes as a string "Form1".
I don't know how to create a Form1 reference from a "Form1" text (then it would be easy to create an instance) or how to create an instance directly (MyForm1).
SOLUTION
As sugested, I used reflection to get the form. The only way working for me I found was this:
Dim T As Type = System.Type.GetType(FormName, False)
If T Is Nothing Then 'if not found prepend default namespace
Dim Fullname As String = Application.ProductName & "." & FormName
T = System.Type.GetType(Fullname, True, True)
End If
Dim f2 As New Form ' here I am creating a form and working with it
f2 = CType(Activator.CreateInstance(T), Form)
f2.TopLevel = False
f2.Name = FormName.Replace(" ", "") & Now.ToString("yyyyMMddmmhh")
f2.FormBorderStyle = FormBorderStyle.None
f2.Dock = DockStyle.Fill
I am using VB.net CallByName to set public variable and same function to run a sub method (every form contains RecordID variable and LoadRecords sub):
CallByName(f2, "RecordID", CallType.Set, 111)
CallByName(f2, "LoadRecords", CallType.Method, Nothing)
For testing purposes, I put following into the testing form:
Public RecordID As Int32
Public Sub LoadRecords()
MsgBox("Load records!!!!" & vbCrLf & "RecordID = " & RecordID)
End Sub
Activator.CreateInstance(TypeFromName("Form1"))
TypeFromName Function:
Dim list As Lazy(Of Type()) = New Lazy(Of Type())(Function() Assembly.GetExecutingAssembly().GetTypes())
Function TypeFromName(name As String) As Type
Return list.Value.Where(Function(t) t.Name = name).FirstOrDefault()
End Function
So, let's go with the idea that I have an assembly called "WindowsApp2" and in that assembly I've defined Form1 and Form2. I've also created this module in the same assembly:
Public Module Module1
Public Function GetDoStuffWiths() As Dictionary(Of Type, System.Delegate)
Dim DoStuffWiths As New Dictionary(Of Type, System.Delegate)()
DoStuffWiths.Add(GetType(WindowsApp2.Form1), CType(Sub(f) WindowsApp2.Module1.DoStuffWithForm1(f), Action(Of WindowsApp2.Form1)))
DoStuffWiths.Add(GetType(WindowsApp2.Form2), CType(Sub(f) WindowsApp2.Module1.DoStuffWithForm2(f), Action(Of WindowsApp2.Form2)))
Return DoStuffWiths
End Function
Public Sub DoStuffWithForm1(form1 As Form1)
form1.Text = "This is Form 1"
End Sub
Public Sub DoStuffWithForm2(form2 As Form2)
form2.Text = "This is Form 2"
End Sub
End Module
Now, in another assembly "ConsoleApp1" I write this:
Sub Main()
Dim DoStuffWiths As Dictionary(Of Type, System.Delegate) = WindowsApp2.Module1.GetDoStuffWiths()
Dim formAssembly = System.Reflection.Assembly.Load("WindowsApp2")
Dim typeOfForm = formAssembly.GetType("WindowsApp2.Form1")
Dim form As Form = CType(Activator.CreateInstance(typeOfForm), Form)
DoStuffWiths(typeOfForm).DynamicInvoke(form)
Application.Run(form)
End Sub
When I run my console app I get a form popping up with the message "This is Form 1".
If I change the line formAssembly.GetType("WindowsApp2.Form1") to formAssembly.GetType("WindowsApp2.Form2") then I get the message "Wow this is cool".
That's how you can work with strongly typed objects that you dynamically instantiate.
Dim AssemblyProduct As String = System.Reflection.Assembly.GetExecutingAssembly().GetName.Name
Dim FormName As String = "Form1"
Dim NewForm As Object = Reflection.Assembly.GetExecutingAssembly.CreateInstance(AssemblyProduct & "." & FormName)
If TypeOf (NewForm) Is Form1 Then
Dim NewForm1 As Form1 = CType(NewForm, Form1)
NewForm1.BackColor = Color.AliceBlue
NewForm1.Show()
End If
I currently have about 5 forms in my application. I'm building a 6th form - frmSummary however, I'd like to be able to access it from all forms. in frmSummary I am planning to add a DataGridView, where I'll be displaying data related to that form. I'm thinking that I should either create a global variable such as
dim FrmName as String
In each form I would have a cmdSummary button so that On click_event, I would do something like
frmName ="CustomerInfo"
Currently the way my application is set up is that I hve a mdiForm and within it, each form is a child so on opening new forms I do something like...
Private Sub cmdSummary_Click(sender As Object, e As EventArgs) Handles cmdSummary.Click
Dim NewMDIChild As New frmClientEligibilityReferral()
frmName = "CustomerInfo" --since this will be comeing from frmCustomerInfo
NewMDIChild.MdiParent = MDIform1
NewMDIChild.Show()
MDIForm1.Show()
End Sub
So I do something like that on opening my new form. My question is how can I pass the parameter to my form frmSummary....here's currently what I'm trying to accomplish....
Private Sub FrmSummary_Load(sender As Object, e As EventArgs) Handles Me.Load
Me.MdiParent = MDIForm1
InitializeComponent()
'Here I want to call a function to load the datagridView(with g_frmName)see below...
call LoadDataGrid(frmName)
End Sub
Is something like that a smart idea? Or should I/Can I directly call the function from the previous form?
Just trying to see if I'm on the right track, if not, how can i do it in a sound way?
If there is only one frmSummary, you could make it a singleton.
In frmSummary, put the following code:
Private Shared _instance As frmSummary
Private Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
End Sub
Public Shared Function GetInstance() As frmSummary
If _instance Is Nothing Then
_instance = New frmSummary()
End If
Return _instance
End Function
Public Sub PutDataInGrid(data As Object)
Me.DataGridView1.' put data in it
End Sub
And you would access it from other forms like this
Dim myFrmSummary = frmSummary.GetInstance()
myFrmSummary.PutDataInGrid(myData)
If I understand the question correctly....
You can just set the required parameters in the New declaration sub (Where InitializeComponent() is supposed to be). On your form, declare variables and set one to each of the parameter values, and set up your form this way..
An example might be;
Public Class frmSummary
Dim var1 as String = ""
Dim var2 as Boolean = True
Public Sub New(ByVal parameter1 as String, ByVal parameter2 As Boolean)
var1 = parameter1
var2 = parameter2
InitializeComponent()
End Sub
Private Sub frmSummary_Load(sender as Object, e As EventArgs) Handles MyBase.Load
If var1 = "This String" Then
If var2 = False Then
sql = "SELECT * FROM myTable"
' Rest of your code to get the DGV data
DataGridView1.DataSource = Dt
Else
End If
End If
End Sub
Again, I may have misunderstood the question, so apologies if that is the case.
In the code below b textbox will contain the string "a.text" what I want b textbox to be the evaluation of the content of the string "a.text" which is the word Test. Please don't suggest:
b.text = a.text
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim t As String
a.Text = "Test"
t = "a.text"
b.Text = t
End Sub
End Class
Check out Controls collection of your form. You can find an item based on its name.
Also check out this answer
VB .NET Access a class property by string value
So, you could take your string, split it by the ".", find the control using the Controls Collection, and then get the property using the second half of your string using Reflection.
Of course, if you are just looking for the Text of the textbox, you just need to use the collection and forget the reflection. Like this..
For i As Integer = 1 To 25
.fields("Field" & i).value = Me.Controls("QAR" & i).Text
Next
You can do what you asked for using Reflection ... I'm not an enormous fan of it for something like this, but here's how it would look in your code:
Imports System.Reflection
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
a.Text = "Hello"
Dim t As String = "a.Text"
b.Text = DirectCast(SetValue(t), String)
End Sub
Public Function SetValue(ByVal name As String) As Object
Dim ctrl As Control = Me.Controls(name.Split("."c)(0))
Return ctrl.GetType().GetProperty(name.Split("."c)(1)).GetValue(ctrl, Nothing)
End Function
End Class
This would set textbox a's value to "Hello" and then copy that to textbox b using the reflection method.
Hope this helps!
I have been very interested as of late in interfaces and the ability to further customize them beyond using them in their default state.
I have been researching IList(of T) specifically. The advantages of using generic lists as opposed to ArrayLists has astounded me. Here is a picture of a test. This is the site that goes into further explanation about the Test.
So, naturally I wanted to experiment. When I first iterate through the list with the ForNext method the code works fine. The second time I can't access the name of the Form in the list because it is disposed. Anyone have any insight how I can access the forms properties in the list.
Public Class frmMain
Dim Cabinet As List(Of Form) = New List(Of Form)
Dim FormA As New Form1
Dim FormB As New Form2
Dim FormC As New Form3
Private Sub frmMain_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles _Me.Load
Cabinet.Add(FormA)
Cabinet.Add(FormB)
Cabinet.Add(FormC)
End Sub
Sub displayForm(ByVal aForm As Form)
Dim myFormName As String = ""
Stopwatch.Start()
If aForm.IsDisposed = False Then
aForm.Show()
Else
myFormName = aForm.(How do I access this objects Name?)
aForm = New Form '<----- I would rather simply use aForm = New(aForm)
aForm.Name = myFormName
aForm.Show()
End If
Stopwatch.Stop()
Dim RealResult As Decimal = (Stopwatch.ElapsedMilliseconds / 1000)
Debug.WriteLine(RealResult)
Stopwatch.Reset()
End Sub
Private Sub btnForEach_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnForEach.Click
'Dim instance as List
'Dim action as Action(of T)
'instance.ForEach(action)
'action = delegate to a method that performs an action on the object passeed to it
Cabinet.ForEach(AddressOf displayForm)
End Sub
I really don't understand why if VB knows that this is a Generic list, which means it is knowledgable of the list's type, and the objects are all constrained to be forms; why I can't call a constructor on an item in the list. Ex. aForm = New aForm or aForm = New Cabinet.aForm
Tear this one open for me somebody. Thanks.
You can't construct a new instance of "aForm" because its isn't a type, it is an instance of type Form.
If you wanted to prevent the ObjectDisposedException, you could hide the form instead of closing it. Place the following code in each forms code behind:
Public Class Form1
Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
Dim form = CType(sender, Form)
form.Visible = False
e.Cancel = True
End Sub
End Class
This is a bit hacky, however, but then you wouldn't need the code in the Else block.
Edit
You could try this instead:
Private Sub displayForm(ByVal aForm As Form)
Dim indexOfCab As Integer = Cabinet.IndexOf(aForm)
If indexOfCab <> -1 Then
If aForm.IsDisposed Then
aForm = CreateForm(aForm.GetType())
Cabinet(indexOfCab) = aForm
End If
aForm.Show()
End If
End Sub
Private Shared Function CreateForm(formType As Type) As Form
Return CType(Activator.CreateInstance(formType), Form)
End Function
You wouldn't need that big Select statement.
This is the only way I have been able to get it to work. I feel it is extremely inefficient however, and hope someone can set me on a path to a better way to do this. The below is what I'm trying to achieve.
Sub displayForm(ByVal aForm As Form)
Dim myFormName As String = ""
If Cabinet.Contains(aForm) Then
Dim indexOfCab As Integer = Cabinet.IndexOf(aForm)
Dim ObjForm As Form = Cabinet.Item(indexOfCab)
If aForm.IsDisposed Then
Select Case indexOfCab
Case 0
aForm = Nothing
aForm = New Form1
Cabinet.Item(indexOfCab) = aForm
Cabinet.Item(indexOfCab).Show()
Case 1
aForm = Nothing
aForm = New Form2
Cabinet.Item(indexOfCab) = aForm
aForm.Show()
Case 2
aForm = Nothing
aForm = New Form3
Cabinet.Item(indexOfCab) = aForm
Cabinet.Item(indexOfCab).Show()
End Select
Else
Cabinet.Item(indexOfCab).Show()
End If
End If
End Sub
Hey all, i have converted some C# PayPal API Code over to VB.net. I have added that code to a class within my project but i can not seem to access it:
Imports System
Imports com.paypal.sdk.services
Imports com.paypal.sdk.profiles
Imports com.paypal.sdk.util
Namespace GenerateCodeNVP
Public Class GetTransactionDetails
Public Sub New()
End Sub
Public Function GetTransactionDetailsCode(ByVal transactionID As String) As String
Dim caller As New NVPCallerServices()
Dim profile As IAPIProfile = ProfileFactory.createSignatureAPIProfile()
profile.APIUsername = "xxx"
profile.APIPassword = "xxx"
profile.APISignature = "xxx"
profile.Environment = "sandbox"
caller.APIProfile = profile
Dim encoder As New NVPCodec()
encoder("VERSION") = "51.0"
encoder("METHOD") = "GetTransactionDetails"
encoder("TRANSACTIONID") = transactionID
Dim pStrrequestforNvp As String = encoder.Encode()
Dim pStresponsenvp As String = caller.[Call](pStrrequestforNvp)
Dim decoder As New NVPCodec()
decoder.Decode(pStresponsenvp)
Return decoder("ACK")
End Function
End Class
End Namespace
I am using this to access that class:
Private Sub cmdGetTransDetail_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdGetTransDetail.Click
Dim thereturn As String
thereturn =GetTransactionDetailsCode("test51322")
End Sub
But it keeps telling me:
Error 2 Name 'GetTransactionDetailsCode' is not declared.
I'm new at calling classes in VB.net so any help would be great! :o)
David
Solved
Dim payPalAPI As New GenerateCodeNVP.GetTransactionDetails
Dim theReturn As String
theReturn = payPalAPI.GetTransactionDetailsCode("test51322")
You're probably getting that error because you need to call it like this:
Private Sub cmdGetTransDetail_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdGetTransDetail.Click
Dim thereturn As String
Dim myTransaction as new GetTransactionDetails
thereturn = myTransaction.GetTransactionDetailsCode("test51322")
End Sub
Or you can make the function be a public shared function and access it as if it were a static method
Your GetTransactionDetailsCode method is an instance method of the GetTransactionDetails class, which means that you need an instance of the GetTransactionDetails class in order to call the method.
You can do that like this:
Dim instance As New GetTransactionDetails()
thereturn = instance.GetTransactionDetailsCode("test51322")
However, your method doesn't actually use the class instance, so you should change your GetTransactionDetails class to a Module instead.