Hi all
I have handle of a usercontrol on external application in vb.net.
I know class type of that user control.
I want to get refrence to that object to check some properties of that object.
Is it possible and how?
thanks
I hope I do understand your question right...
You may try to insert a reference to your library (I assume your userControl is in this library). As a prerequisite this external application must be written in .Net or have some kind auf COM interface!
Then you may try to access the userControl class by
NAMESPACE.CLASS myReference = new NAMESPACE.CLASS();
hth
You can get some info by using interop, with some functions like GetWindowText and SendMessage, however this won't allow you to get all properties, and won't work on every type of application (WPF or Java come to mind).
The Control Class has a method FromHandle:
Dim myCtrl As knownType = Control.FromHandle(knownHandle)
'then get the known property using Reflection
Dim oProp As System.Reflection.PropertyInfo = myCtrl.GetType.GetProperty("KnownProperty")
Dim oValue As Object = oProp.GetValue(myCtrl, Nothing)
'or directly:
Dim oValueD as Object = myCtrl.knownProperty
I don't know if it works between processes.
Related
I've been told to think outside the box, and think of a way to create an object in VB without using the new keyword. I was told it is possible but i'm having trouble figuring it out. I know primitive data gets stored on the stack and the reference to the objects get stored there too but the actual memory space for the object is in the heap and that new does that for us. When i try it without new i mostly get null reference exception, any ideas on how this is possible?
Dim objTest as TestOne()
'some class named TestOne with empty Constructor
In VB you can use the CreateObject function if you have an existing class defined in a COM library that you've created - or a COM library that already exists.
As an example, create a project reference to the Microsoft Scripting Runtime COM library (scrrun.dll). To do this in the VB IDE select Project, References, then pick the reference 'Microsoft Scripting Runtime'. You can then write the following code:
Dim fso As Object
fso = CreateObject("Scripting.FileSystemObject")
I haven't done VB for quite a while now, but the Activator exists in both C# and VB. Here's couple lines of C# that you can convert to VB:
var newThing = (TestOne)Activator.CreateInstance(typeof(TestOne));
newThing.ID = 5;
The CreateInstance method returns an object, which I convert to the correct class with
(TestOne)
which is the C# syntax for type conversion. Sorry, I forgot how to do this in VB.
Where class 'TestOne' looks like:
class TestOne {
public int ID { get; set; }
}
Note that 'Activator' is part of .NET reflection.
I am working with a COM library in Visual Basic (VB.NET). I am trying to get a list of properties associated with an Interface; however, I am not able to get a list of interface properties. Can someone direct me on the best way to list properties on an Interface?
Below is some sample code that loops over all the properties of a class called "TextBox". The output from this code is a list all the class properties.
This particular code doesn't seem to work for interfaces. By this I mean that this code doesn't return the properties of an interface.
Dim txt As New TextBox
Dim type As Type = txt.GetType()
Dim properties() As PropertyInfo = type.GetProperties()
For Each p As PropertyInfo In properties
OutputWindow(p.Name)
Next
Image of COM Library with Interface HYSYS.Valve
Just replace txt.GetType() with the GetType() operator to specify type names instead:
Dim type As Type = GetType(HYSYS.Valve)
You would only use <object>.GetType() when you already have an existing instance of an object. To get the properties of a type in general, for instance a TextBox, it is better to do GetType(TextBox).
I'm new to VB and I'm currently migrating a vb6 app I did not write to .net and I'm struggling with this error,
If TypeOf Application.OpenForms.Item(i) Is frmAddChangeDelete Then
'UPGRADE_ISSUE: Control ctrlAddChangeDelete1 could not be resolved because it was within the generic namespace Form. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="084D22AD-ECB1-400F-B4C7-418ECEC5E36E"'
If **Application.OpenForms.Item(i).ctrlAddChangeDelete1.ParentFormNumber = intFormNumber** Then
If Application.OpenForms.Item(i).Text = "Add Proofed Expense Items" Then
boolAddProofed = True
Exit For
ctrlAddChangeDelete1 is supposedly calling the friend class ctrlAddChangeDelete from a separate VB file, so I'm not sure why it's saying that
"'ctrlAddChangeDelete1' is not a member of 'System.Windows.Forms.Form'."
Any help is appreciated, thank you !
Application.OpenForms is a collection not strongly typed.
When you reference elements there you get back a generic Form.
In a generic Form there is no control named ctrlAddChangeDelete1
If you have a form derived class named frmAddChangeDelete and this class has a control named ctrlAddChangeDelete1 then you need to cast the reference stored in the OpenForms collection to your specific form class before trying to reference that control.
Moreover, to access that control from external code, you should also have the Modifiers property set to Public instead of the default Internal. Otherwise you will not be able to access the control from any code external to the class.
To retrieve correctly your form you can write
Dim delForm = Application.OpenForms.
OfType(Of frmAddChangeDelete)
FirstOrDefault()
If delForm Is Nothing Then
' No form of type frmAddChangeDelete is present in the collection
' write here your message and exit ?
Else
' Now you can use delForm without searching again in the collection
......
The code above uses the IEnumerable.OfType extension and this requires the Imports System.Linq.
If you don't want to use this then you can always use the TryCast operator to get the reference to the correct class
' Still you need a for loop up ^^^^ before these lines
Dim delForm = TryCast(Application.OpenForms(i), frmAddChangeDelete)
if delForm Is Nothing then
....
else
....
When reading an old project of mine I found something suspicious where I don't really understand why this part is working:
Public Shared Sub getXMLforProject(QueryString As String)
Dim linkStart As String = "http://example.org"
Dim linkEnd As String = "&tempMax=2000"
Dim target As String = linkStart & QueryString & linkEnd
'replaces parts that need encoding,
'groups(1) is the sign e.g. <= and groups(2) is the text that needs encoding
'groups(0) is the text of the full match (sign and encoding text)
target = rx.Replace(target, Function(m As Match) encodeURLString(m.Groups(1).Value) + encodeURLString(m.Groups(2).Value))
GUI.WebBrowser.Navigate(target)
Return True
End Sub
the respective path that seams suspicious to me is the line
GUI.WebBrowser.Navigate(target)
There is a class called GUI that realises the user interface, but in the file context there is no objects named "GUI" available, so the access must be done by using the class. How is it possible for this to work? Is there an implicit mechanism that redirects the call from the GUI-class to the GUI-object?
You are using VB.NET, it emulates the behavior of the Form class from earlier Visual Basic editions where using the type name was a legal way to refer to an instance of the class. Kinda necessary to give programmers a fighting chance to convert their VB6 projects. Underlying plumbing is the My.Forms object.
So, 99.9% odds are that the GUI class derives from System.Windows.Forms.Form. Especially given that it has a WebBrowser member. The Form is the host window for the browser.
please help me on creating a user control object in runtime using createobject function or whatever better function in vb.net.
here is my code:
Dim b As New Security.Sec_Role
b.Name = "Sec_Role"
b.visible = true
but i want to use this code:
dim b as object
b = createobject("Security.Sec_Role")
but it always return an error:
Cannot create ActiveX component.
EDIT: i figure it out..thanks a lot..i use this codes:
Dim asm As System.Reflection.Assembly = Assembly.Load("Security")
Dim b As Object = Activator.CreateInstance(asm.GetType("Security.Sec_Role"))
If it is an .Net UserControl you will not be able to use CreateObject unless it has been exposed as a Com object according to the MSDN page for CreateObject. Using New would be the proper way to create a .Net UserControl.
From above link:
Creates and returns a reference to a COM object. CreateObject cannot
be used to create instances of classes in Visual Basic unless those
classes are explicitly exposed as COM components.
From this MSDN Forum try something like this using System.Activator.CreateInstance:
Dim oType As System.Type = Type.GetType("MyNamespace.ClassName")
Dim obj = System.Activator.CreateInstance(oType)
.Net classes are not ActiveX controls.
You can't do that.
You may be looking for Reflection or a dictionary.
You will want to use Activator.CreateInstance:
Dim b as object
b = Activator.CreateInstance(Nothing, "Sec_Role")
It will be easiest if this method is in the assembly which has the controls. Otherwise, you will need to provide the assembly name in the first parameter.