What I want to do is pass a Type to another object's constructor, where the other object creates a new instance of Type. I can create a constructor with a parameter declared as System.Type without problem, but when I try to instantiate it tells me there is no such type.
Public Sub New(targettype As System.Type)
Dim Test As System.Windows.Forms.Form = New targettype
End Sub
I don't know if this has been asked before, but we're having a discussion about it today at my job. Should private variables (that are shared/static) be instantiated when they are dimensioned/defined, or is it a better practice to do this inside of a constructor?
Public Class IpCam
Private Const HOST As String = "http://test.com/url/example"
Private Shared _Example As New OurClass(HOST)which one to use?
[code].....
I have an abstract class which requires a delegate to function. I pass the delegate into the constructor. Now that I have a non default constructor I need to call the abstract class's constructors from the concrete class which means that I need to use MyBase.New(...). I have included a quick example below.
Public MustInherit Class BaseClass
Public Delegate Sub WorkMethod()
Private _Work As WorkMethod
[code]....
I have tried to do this but I keep getting the following error: "Implicit reference to object under construction is not valid when calling another constructor".Can I not do what I am trying to do above? I initially had the delegate setup in its own setter method. But then I am creating a deceptive API because it does require a point to a method to work properly.
how to pass value other than from constructor.
In my code....value are usually passed through constructor.
ie everything is declared in constructor and while executing, these values are defined in new object.
Implementing a simple MVC in vb. The controller instance creates and holds instances of the model and view:
Public Class Controller
Public Property myModel As Model
Public Property myView As View
[code].....
I've constructed a custom System.Windows.Forms.Form that requires arguments to New. I want to use one of these as the MainForm in a Windows Forms Application. How do I get the Application Framework to pass those arguments as needed?
View 1 RepliesI've been trying implement Constructor method in passing variable between two forms.Just a rough user interface guide - issue Invoice. User would type in all the Customer Name, Document Number. Once he reached Item Details, a Child Form would pop-up for the User to select/search the Invoice's Item; Once selected, the selected item would showed in the primary Form.
What I had tried is, the Constructor method worked perfectly when it is self-contain in a new project, yet to be implement in my application.But when I implemented, there is an error: Reference to a non-shared member requires an object reference.
[Code]...
How do I get using reflection the most generic type from a shared constructor in the base class :
Public Class Foo()
Shared Sub New()
'Here we have code to get the type[code]....
I expect the result to be Bar type and not the Foo. Is it possible?
I have this code to get the default constructor:
Public Function f(ByVal t As System.Type) As Object
Return t.GetConstructor(New System.Type() {}).Invoke(New Object() {})
End Function
I need to pass values to the Constructor as
Public Function f(ByVal t As System.Type) As Object
Return t.GetConstructor(New System.Type() {someInteger,someString,etc.etc}).Invoke(New Object() {})
End Function
Also I have 3 classes of Type T, with all having different parametric constructor. It's important for me to have it generic as the Classes of type T might increase in future with less or more parameters.
I've been having problems with following code on some computers, while it's worked super on others (most):
Dim xmlSer As New System.Xml.Serialization.XmlSerializer(GetType(XMLContext))
which produces the stacktrace:
System.ArgumentNullException: Value cannot be null.
Parameter name: type
at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
How can that code throw that exception, when the argument is drawn from a gettype call, and note that it doesn't happen when debugging on my own PC, only when it's installed on some of the client PC's???
I'm passing a type name and some parameters from C# code into a navigation framework written in VB. The navigation framework looks for a constructor on the type that matches the parameters passed in using Type.GetConstructor(Types()). The constructor that I'm looking for expects an array of integers Integer() in vb. But it gets an array of System.Int32. I've gone so far as to try this:
[Code]...
And the VB code still sees System.Int32 on the other end, which means that it doesn't find the constructor.
After debugging a particularly tricky issue in VB.NET involving the order in which instance variables are initialized, I discovered that there is a breaking discrepancy between the behavior that I expected from C# and the actual behavior in VB.NET.Nota bene: This question concerns a slight discrepancy in the behaviors of VB.NET and C#. If you're a language bigot that is unable to provide an answer other than "that's why you should use C#, noob", there is nothing for you to see here; kindly move along.Specifically, I expected the behavior outlined by the C# Language Specification (emphasis added):
When an instance constructor has no constructor initializer, or it has a constructor initializer of the form base(...), that constructor implicitly performs the initializations specified by the variable-initializers of the instance fields declared in its class. This corresponds to a sequence of assignments that are executed immediately upon entry to the constructor and before the implicit invocation of the direct base class constructor. The variable initializers are executed in the textual order in which they appear in the class declaration.
Contrast that with the portion of the VB.NET Language Specification concerning Instance Constructors, which says (emphasis added): When a constructor's first statement is of the form MyBase.New(...), the constructor implicitly performs the initializations specified by the variable initializers of the instance variables declared in the type. This corresponds to a sequence of assignments that are executed immediately after invoking the direct base type constructor. Such ordering ensures that all base instance variables are initialized by their variable initializers before any statements that have access to the instance are executed.
The discrepancy here is immediately obvious. C# initializes class-level variables before calling the base constructor. VB.NET does exactly the reverse, apparently preferring to call the base constructor before setting the values of instance fields.If you want to see some code, this related question provides a more concrete example of the divergent behavior. Unfortunately, it does not provide any hints as to how one might coerce VB.NET into following the model established by C#.
I'm less interested in why the designers of the two languages chose such divergent approaches than I am in possible workarounds for the problem. Ultimately, my question is as follows: Is there any way that I can write or structure my code in VB.NET to force instance variables to be initialized before the base type's constructor is called, as is the standard behavior in C#?
I got 2 classes in a form, and I would like to pass a value from a textbox to the other class, so I decided to use Deligate.
Below is the code.
Public Delegate Sub delPassSize(ByVal text As TextBox)
'To get size from Class Calculate(Class 2)
Public Sub GetSize(ByVal txtForm1 As TextBox)
[code]....
and the error message is 'cls.Getsize is a delegate type and requires a single 'addressof' expression as the only argument to the constructor.'
I wish to put the XMLSerializer behind a 'facade' class of mine so that user wont have to supply type info to the constructor. But doing this has a problem. Consider this class:
Class XmlFormatter
Private Shared xs As XmlSerializer
Public Function Deserialize(ByVal serializationStream As Stream) As Object
Dim o As Object = Nothing
[code]....
The problem is that the user of this class cannot use Deserialize without first using Serialize because the XMLSerializer instance is created in Serialize and it is shared. But using Deserialize without this instance will simply return Nothing.
i am getting all filenames from a directory.parsing out the directory names & the .vb extension then converting those filesnames to classes.Every file in the LPCriteria direcotry is its own class with a "Evaluate" function.[code]
View 1 Replieswhat's the rationale behind this limitation: Constructor call is valid only as the first statement in an instance constructor i want to pass an argument to my constructor which validates this argument and calls mybase.new according to this argument but it doesn't let me
example:
Public Class prob
Inherits System.ApplicationException
Public Sub New(ByVal problem As String, ByRef inner_exception As Exception)
[code]....
I have the following sub which works for the type "Button". I would like to make it general by having a parameter that is assigned a type rather than "Button" being hard wired. Can this be done? How do you pass a type? I tried the parameter "ByVal t as Type" but the compiler complained when I used t as a type and I also tried inserting (Of T)but the compiler complained about CType(control,T).
how add type as an input to this sub?
Public Shared Sub Example(ctrl As Control, items As ToolStripItemCollection)
For Each control As Control In ctrl.Controls
If TypeOf control Is Button Then
Dim butt As Button = CType(control, Button)
determine which component had been clicked?
I create a object type entity in the main function and would like to pass it to a separate class, do some calculation, and then pass the result back to the main function. But I keep getting errors, can someone point me where I did wrong? It's in windows application[code]...
View 2 RepliesI get a compile error Type "ctltype" is not defined with this code.
This is .NET 1.1 legacy code so not good I know.[code]...
After reading this post i realized that i cannot pass an anonymous type as a parameter to a function. So what other options do i have?
Perhaps, passing a Query.ToList as parameter would help, or am i re-inventing the wheel?
Update: I have the following query, which i would like to pass to a function:
Sub Test
Dim Query = (From c In DB Select New With { .ElementName = c.Name })
DoSomething(Query)
[Code].....
I have a following code which works fine
MsgBox(AddSomething(Of String)("Hello", "World"))
Public Function AddSomething(Of T)(ByVal FirstValue As T, ByVal SecondValue As T) As String
Return FirstValue.ToString + SecondValue.ToString
[code].....
I have situation where I have to retrieve different fields from Access Database and put into one RichTextBox but they have to be displayed as DIFFERENT font types/colors.
I am able to get the database field data into RichTextBox but not able to set font styles or font colors. They are displayed in default font style. Please help me with sample code by giving example, i.e., taking two to three different string types and sending them to RichTextBox with different font color and styles.
I'm trying to create a function that searches up a WebControl's parent-child relationship (basically the opposite of WebControl.FindControl(id as String), but looking for a specific WebControl type).
Example
I have a user control in an ItemTemplate for a GridViewRow. I'm trying to reference the GridViewRow from the user control. The user control may or may not be inside a div or other types of controls, so I don't know exactly how many parent's up to look (i.e. I can't just use userControl.Parent.Parent). I need a function that will find the first GridViewRow that it finds on the way up the parent-child hierarchy.
I have the following generic method : Namespace Helpers
[Code]...
I would like to use type interference so that when i call ToGenericType method, I would not need to pass the type(t) This is how i call ToGenericType now.......
[Code]...
I'm creating buttons programatically. I want to create an ExportToExcel and ExportToWord button.
I created this class to pass the type of export as EventArgs:
The exportType is an Enum
Public Enum ExportType
nsExcel
nsWord
[Code]....
I use jQuery ajax calls to ASP.Net web services (ASMX files) to update the web page data.
I have the database storing code seperate from the domain object class code (in the example code below, there is an Animal class and an AnimalRepository class). I'm implememting a convention that all similar domain object repository classes will have a Store method .
I would like to create a web service that can cater for calling the Store method for any one of these repository classes. To get this to work, in the below code sample, the List(Of Animal) parameter would need to be a generic type.[code]...
I have a class:
Form
Public Class Form1
Dim teamlist(2) As team
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
teamlist(0) = New team(1, "one", "First")
[Code] .....
Error I'm getting is too many arguments.
I am having some real issues with this one. I have a class which contains two other objects...but I cannot seem to instantiate those sub objects. Here is the code for my class:
Option Explicit On
Public Class Boot
'A collection of Heads and Shells
[Code]....
Notice the count for my two objects, Ohead, and oShell, is zero. Im not sure why this doesnt instantiate properly, as I believe is what is going on.
I can't find what's going on with the following nHibernate HQL.
here's my VB.Net code:
Return _Session.GetNamedQuery("PersonAnthroSummary").SetInt32(0, 2).UniqueResult()
My Named Query:
[code].....
I just like to know if how can i do single form instantiation upon loading my Form..upon loading my MainForm it automatically detect if that MainForm is still exist..ive try putting my code in the contructor of my MainForm..i check through the process in the task manager if that MainForm is still exist..but i think this is not the good idea bcoz..the MainForm takes several seconds to appear..and i think this is bcoz i loop through the process.
View 1 Replies