Constructing An Object And Calling A Method Without Assignment
Apr 15, 2010
I'm not entirely sure what to call what C# does, so I haven't had any luck searching for the VB.Net equivalent syntax (if it exists, which I suspect it probably doesn't).
In c#, you can do this:
public void DoSomething() {
new MyHelper().DoIt(); // works just fine
}
But as far as I can tell, in VB.Net, you must assign the helper object to a local variable or you just get a syntax error:
Public Sub DoSomething()
New MyHelper().DoIt() ' won't compile
End Sub
Just one of those curiosity things I run into from day to day working on mixed language projects - often there is a VB.Net equivalent which uses less than obvious syntax. Anyone?
Use the "new" keyword to create an object instance & Check to determine if the object is null before calling the method. I'm reading text from a text file using the following [Code]
I've been working in .NET for some time now, but occasionally I still get confused by a disparity between the framework and my prior experience in C++.In .NET, all objects are either value types or reference types. Reference types are allocated on the heap while value types are allocated on the stack (in the current CLR implementation, anyway). I get that. However, at least in VB.NET, you can still define a constructor on a value type.
Public Structure Coordinates Public x As Integer Public y As Integer
I've used VB.net for several years now, but keep coming across little quirks that I don't know how to work around. Curiosity finally got the best of me, so I ask now: is there a way to create an object without assigning it?For example, say I have an Engine class, that I want to instantiate and have it immediately do whatever it needs to do. If there's nothing I need to do with Engine after creating it, I have, till now, done something like:dim myEngine as new Engine()Is there a way to avoid the "dim myEngine as" part? You certainly can in Java. I could just create an object with "new Engine()" in java and not assign it to anything.
Why do I need this? Because often I want to create a delegate object (hence I called it "engine") that performs some functionality, but otherwise I don't need to ever reference it. I used to have such objects have a "public sub perform", but have found that cumbersome -- I'd rather just create the object and not worry about remembering to call its perform method. And I find it aesthetically displeasing to create references to objects that I don't intend to use
When I am loading an Assembly dynamically, then calling a method from it, I appear to be getting the method from Assembly executing before the code in the method that is calling it.It does not appear to be executing in a Serial manner as I would expect. Can anyone shine some light on why this might be happening. Below is some code to illustrate what I am seeing, the code from the some.dll assembly calls a method named PerformLookup. For testing I put a similar MessageBox type output with "PerformLookup Time: " as the text. What I end up seeing is:
First: "PerformLookup Time: 40:842" Second: "initIndex Time: 45:873" Imports System
Maybe this is a n00bish question, but I'm used to c++'s pointers and references and this is confusing me a bit. Let's say I have the following scenario in a VB.net application:
[Code]...
The situation is this: I have a collection of objects, and during execution of the program, any of them can be fetched from the collection to be used/edited by another part of the program. Now obviously if I edit the data inside the object it is allright, but what if I want to replace the object, as I did above at line 5? I would change only the local reference (y) but not the object inside the collection!
Is there a way around this? How can I take with me a "reference to the object's reference", instead of just a reference, so if I reassign it it will also reassign the one in the collection? I hope I'm making myself clear, unfortunately english is not my native language, to be clear: in c++ this would be easy using a pointer to a pointer, or passing a pointer to the object always by reference, so calling new or reassignment on it would change the original pointer itself)
Let's say I have a page Test.aspx along with test.aspx.vb.Test.aspx.vb contains a class name "TestClass". In that class I have method1(), method2() and method3()I need to be able to call one of those methods, but I can't hard code it, the method to be executed comes from a string.
I can't do Select Case StringContainingTheNameOfTheDesiredMethod Case "Method1"
I hope the question makes sense, anyways. I'm looking to know if in VB.NET, when we call an object's constructor, is there some kind of a reference that points back to the caller? I'm interested because of a corner case where I want the object being created to first be able to validate the existence of some data in the caller before it allows itself to be created. If this validation fails, I plan on throwing an exception. This corner case will never happen at runtime unless the object being created is used improperly by a programmer. The object being created is not inheriting the object I want it to validate, so I can't do anything with the MyBase qualifier.
It's bit of a "future-proofing" issue that I have a (bad) habit of doing. Not critical -- I can always leave stern comments behind as a last resort. Wanted to know if this was possible.
I call the function GetDataTable and when it gets to the return line, I get the error message: Object reference not set to an instance of an object.
Dim DB As New DBConn Dim gd As New DataAccess.GetData Dim DT As New DataTable
[Code].....
Updated. I'll see if I can update with the DataAccess.GetData code. I didn't originally put it in there because our shop use it all the time and have no issues with it.
Basically i've got a web service that i'm trying to put some kind of usage logging in. To do this i've created a class with a logging method. I instatiate the class on the service and then call the logging method in each of the web methods.
I have a .dll file (Interop.ACTMULTILib.dll) that I use to connect to a PLC. This .dll contains a sub called ReadDeviceBlock2(byval devicename as string, byval size as integer, byref data as short).My console application startup thingy is a module. When I call this method in my main it works fine, if I call it from another method that was called by main it works as well.However, it doesn't work when I call it from my Timer_Elapsed sub? I guess this has to do something with threads but I can't figure it out.
Module Main Private Timer As New System.Timers.Timer Private PLC As New ACTMULTILib.ActEasyIF Private DataSet As new DataSet
I have a project that has some VB code in it that I'm not allowed to convert to C#. I work in C# and not very good at VB, but I am needing to modify that VB code to use some C# methods I created.
For example:
C#: Code: using MGCIS2.Reporting; using CrystalDecisions.Shared;
[code]....
At this line in the VB code (Dim crv As New Tax.Reports.CrystalReportViewer(_rdbc)) it is giving me an error:Too many arguments to 'Public Sub New()'
I am having some problems calling the First() method of the System.Collections.ObjectModel.Collection(Of T) class. My front-end web application is VB.Net 3.5, and the data access layer is C# 3.5. Here is pretty much the sample code I have:
I have a form call form1 which is a mdi tab. Within form1 there is a datagridview and a button. When the button is clicked it will fire a method within form1 to update and repopulate the dgv.
Now my problem now is that I have another form call form2 which I load using .showdialog. Whenever I update the data within form2, it will fire method from form1 and update the dgv in form1. However the dgv doesn't seem to repopulate the updated data.
I've got some debugging code that looks like this[code]...
The purpose of this code is to output the name of the calling method. Now, I would like to output the FILENAME where the calling method resides. Is this information available?
I am using a .dll called Kiosk in my application which is resonsible for disabling some keyboard keys. I am doing like this... using Kiosk; public static Kiosk.Kiosk KIOSK = new Kiosk.Kiosk();
essentially I need to create a class that houses the methods and then call the methods in the form but I can't seem to find out what the right code is to call it. I think there may be an issue with the conversion from a double to a string.
This is what I have for the Class
Public Class Aircraft Dim Names() As String = {"A-747", "A-737", "C-150", "D-240"} Dim TakeOffVelocity() As Double = {250, 264, 270, 240} Dim Acceleration() As Double = {33.5, 44.2, 37.1, 51.9}
Lets say I have a application with these three items: A startup form called form1 A class lets say Class1 A class lets say Class2
How can I access a method in class2 from within class1? For example in Class2 I have a method call AddToDatabase(sql as string) and in a method is Class1 I have a SQL statement that I want to implement.
Solution that didn't work: Initializing an instance of Class2 in form1 called myClass2 and trying to reach it using: form1.myClass2Initializing an instance of Class2 in New subrotine of Class1 and trying to call it through: myClass2
So after i add the values to the list, for example : element.ThirdElement() will have the value from attribute3 ("Send"). Also element.secondElement() will retain the value from attribute2 and so on.
I have a logging class that stores entries in a datatable dt. I then use SQLBULKCOPY to write that dt out to a sql table. Basic stuff. Problem is, I'd like to only call SQLBULKCOPY when there's say 50 entries in the dt. The problem is, what if I'm done (either intentionally or not, like if the code block that's using the log class throws an exception) with the logging object and there are still 15 rows in the dt?
I am writing a alternative to GDI, and rigth now i am working at a logging function. The idea is that while you use the class to draw, it will write a logg of what you have done, which can be used to draw it back later. In that way i would be able to store a drawing with weary little disk usage.
I'm working on a base class right now, here's a basic rundown of it:[code]The problem is, in the Public Class bar example, some classes may implement MyInterface, and others don't. What I'd like to be able to do is have the sub New() in the structure in the base class "Foo" be able to tell if the class calling it (either the Base class, or the child class) implements MyInterface or not.
