Build A Class That Works With A Form?
Sep 7, 2010
I am trying to build a class that works with a form, but I keep getting the dreaded "Object reference not set to an instance of an object" Error.The form basically collects test grades and assigns them to a collection.My class code is as follows:
Public Class Scores
Private colScoreCollection As New Collection
Public mintSum As Integer
Public mdecAverage As Decimal
Public mintMinimum As Integer
[Code]...
I had a similar project I was working on that had a collection in it, but now that one is giving me the same error. It there something with my version of Visual Studio that is causing this error possibly?
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Feb 15, 2012
I have a Form with a Media Player in it. Which plays a Song.
[Code]...
It's playing in the background since the Form is hidden. When I play itin Debug, everything works fine. When I run the app outside Debug, I get this error: [URL] The Music File is there, but strangely, there comes this weird error.
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Nov 18, 2009
I'd like to build a class where I always have a button at the bottom of a form.Then when I drag and drop the button, It has to make a copy of that button called "button1", if I drag and drop the button again I'll have another button called "button2" and so on.But If I drag and drop the "button1" or "button2" they shouldn't duplicate as the original. And this is the problem I can't sort out.
This is my class:
Imports System.Windows.Forms
Imports System.Drawing
Public Class frmTablesEditor
Inherits Form
[code].....
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Apr 9, 2010
I am trying to create a class in VB.NET which inherits a base abstract class and also implements an interface. The interface declares a string property called Description. The base class contains a string property called Description. The main class inherits the base class and implements the interface. The existence of the Description property in the base class fulfills the interface requirements. This works fine in C# but causes issues in VB.NET.
[Code]...
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Feb 27, 2012
Updating the TextBox from a Thread that calls a function within a Class does not work. I'm trying to get this to work in a DLL (but I tried without as well). The DLL is accepting an Object as an argument[code]....
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May 9, 2012
I'm working on a windows form project where the first form displays a menu list made up of custom textbox controls. When the user navigates to a textbox and presses enter the underlying code runs another form and hides the menu form. The form to run and the navigations sequence is controlled by properties I added to the custom textbox. I have done the same with a custom button. Both custom control inherit from their respective Windows.forms controls.
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Nov 13, 2009
Enviro: 2007 Exchange Server, 2 Intranet servers (1 deploy, 1 dev) running .NET 2.0 app - all within same network / behind firewall. I am working on a legacy app by our previous web guy, when our sysadmin upgraded to exchange 2007 and put it on a new server all of the mail functions in old app broke. Had to upgrade to .NET 2.0 (from 1.x) and nothing worked untill I tried new SMTP code in a local function in the codebehind of a page of the app instead of calling a class, as follows:
Function SendNow(ByVal strFrom As String, ByVal strTo As String, ByVal strSubject As String, ByVal strBody As String) As Object
Dim msg As New MailMessage()
Dim smtp As SmtpClient
[code]....
So the above works fine, in that file. The problem is that the app was designed to call a class that resides on the dev server. When I move this same code into the class on the dev server I get transport errors. I think this has to do with the fact that we're using integrated authentication with impersonation=true and it seems to get dropped due to the class being on a different server (even though it's behind our firewall).
I could either try moving the classes to the production server or somehow keep the authentication in the class working through the hops. Either way I need to keep the class because it's referenced all over the place (in more than just this app). I am not that savvy in .NET and I cannot figure out where the setting is within the app that defines where the class is imported from. It just seems to be available no matter where the app is deployed. (Working files are on same server as classes, then publish the app to production server).
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Oct 18, 2009
Can I create my own class library, possibly to be sold commercially, in VB.NET?
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Apr 16, 2009
I am trying to build a class. I am having a difficult time conceptualizing how a class is built and how it works. I want to be able to build a USEFUL class and implement it in an application.
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Nov 17, 2011
so my question is relatively simple, can I create VB6 application that references a class in a dll, and then substitute that dll for another at runtime?Now my intial guess is... no chance in VB6.
So my thoughts turned to a VB.net interop dll. Could I do it in here, and then call the interop dll from the VB? but I'd be happy if someone knew differently.The only thing that I think would actually work would be DI in .Net, but I'm limited to .net 2, or 3.5 at a big push, so I dont know if that is possible.
I have a dll that a specific site uses, but we dont want to ship that out to everyone. Instead, we want to build a clone dll which just has the interfaces setup so that the VB6 build will complete.When it gets to the site that needs it, they want to replace the dummy dll, and drop in their version instead.
Note: We do use RegFreeCOM when its gets installed, so I do have the manifest files that I could play around with if needed.
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Nov 8, 2009
I have this application that users can make exams that contain exercises of different ... whatever. Anyway when student takes the exam he chooses it from a list and then all exercises are loaded from database. I wanted to make loading process faster by loading only first exercise data and putting others in background thread.
Actually in other parts of this application something like that is done but not by me. Basicaly an api class is built around BackgroudWorker and i can use this class to put certain functions of objects to be executed in background. The idea sounds great but in real life there are some problems with it. For example for historical reasons this application uses global functions and reader and uses global connection to Access database which means if in background something is being fectched from data base and you try to fetch from database in main thread then a „reader is already open" error occurs. To avoid this error if im doing something in main thread and want to fetch some data i have to move my function from main thread into background worker function list. And basically this in my opinion stinks cuz you end up with many delegātes, invoked checking and thre result... I was just thinking that there maybe is another way to allow (maybe with events) not put everything in background in case something is happening in bakcground but rather allow bgworker to finsih current thing, then do my thing and then resume bgWorker and not create havoc in code.
Basically i have to classes - exam and exercise that each implement many interfaces (like IExercise, IExerciseResult, IExerciseYesNo, IExerciseMultipleChoise etc.)And then i have DataBase classes like ExerciseDB, ExerciseResult etc. That have functions that preparē the sql params and call sqlHelper functions.And for example when i load up exam i go throug all exercises and call LoadData function that in turn calls ExerciseDB function selectData and then i put the returned data in Exercise object. And this type of thing of course would producē error if i at the same time would try to register the answer in database for another exercise. Ofcourse i could always check and put this in background... but as i said i'd rather want to work with database from both threads.
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Feb 14, 2009
Two.JPG
I have build a Car class as follows:
Code:
Public Class Car Dim CarState As Integer Dim CarPicture As New PictureBox
Public Sub DriveIn() 'This sub to drive in the car to the lot. CarState = 1 Dim x As Integer For x = 1 To 45 If x <= 12 Then CarPicture.Top -= 3 Threading.Thread.Sleep(100)
[CODE]...
Then i tried to instanciate many objects of this calss to move more than one car as follows:Public Class Form1
Private Sub btnDrive_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDrive.Click 'Dim objCar As New Car() Dim objCar As Car objCar = New Car objCar.DriveIn() End Sub
[CODE]...
But unfortunately no car moved.
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Mar 22, 2012
I am working on a VB NET project and had the strangest thing happen.I created a class file(just like a dozen or so I have already created). I wrote in the code to access it. The autocomplete found the class, filled it in and colored it blue, just as it should.But, when I run the app, I get a type is undefined error.
There is nothing in the class yet. And there is really no code to post..it is as straight forward as I described.I tried restarting VS; Deleting and recreating the class; Deleting the class and creating a new one with a different name.
Is there something in the VB NET configuration I can check to see if it is not being added somewhere?
I found the problem. I have 2 projects in one solution. They both share some classes that were trying to use my new classes. When I hit F5, both projects are compiled, and since I hadn't shared the classes with the second project, it errored.
So, now my question is changed; How do I specify to only build the specified Startup Project when debugging?
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Apr 15, 2010
I have put this code in the global form Inherits System.Windows.Forms.Form. And then in the form that will inherit this from the global Inherits MenuStrip. "MenuStrip" is what the global form is called. But keep getting this error: Error1Base class 'MenuStrip' specified for class 'Lesson2' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types.
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Aug 18, 2010
Say I have a Framework 4.0 project that is referencing a class library targeting 3.5. The project will simply not build. It won't give me any valid error message it will just act as though the reference does not exist.
Projects that were working like this in Visual Studio 2008 are no longer working in 2010. Took me forever to figure out what there error is. If I remove the project reference and add it back the intellisense lights up and you can tell a variable referenced in the class library is found. But as soon as you build the project everything is lost. My using statements get underlined, references to the variable all turn grey and project fails to build saying the class cannot be found. Once I make the class library 4.0 as well everything builds. I get the same issue between 4.0 client profile and 4.0 as well.
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Jun 16, 2012
It is a word scrambler in which the user must guess the word that is scrambled. It is not completed obviously but the code only works with one form. As soon as I include other forms for title screens and the likes, the code doesn't work at all.Here it is (This is the multiform version):
Imports System.Text
Public Class Form3
Public word As New List(Of String)
[code]...
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Feb 12, 2009
I Need Build a user control which works as a Login control using Windows Class Library or Component Template:The user control returns the user name and the password It means that the control has minimum two ReadOnly Property procedures. You let the user of your control (he/she which uses your control in his/her software) to set the background colour of the two labels. Create a Windows application to test your control.
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Sep 23, 2009
<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-
[CODE]...
I have a customer who is using a VB Script to create one swbemrefresher object which works normally on Win XP and Win2003 platform, but on Windows Vista platform prompts with "invalid class" error...
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Jan 8, 2011
Code:
Private Sub KeyHandling(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
Select Case e.KeyCode
[Code].....
This code won't do anything, except when I hold the control key.
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Feb 9, 2012
I've have found answers here frequently in the past just from browsing. But now I'm completely dumbfounded.
I'm using Visual Basic 2010 Express, on Win7 32bit. My application talks to an Arduino via a virtual com port provided by a cheap Bluetooth to serial adapter. I use a text based protocol that is working fairly well. BUT one method in my code, taht seems functionally equivvalent to the other methods is locking up my whole window.
It does this whether I'm debugging or running the exe.Below are the offending method, and a simmilar one defined above it that works with no problems.
[Code]...
If I comment out the cal to write, everything works fine. Aside from me setting some state bools and playing with button titles in the first method, I can't see the difference as to why one works fine and the other hangs.
I really hope someone has some experience in the SerialPort object and VB that can shed some light on this.I've tried everything I can think of. I thought maybe it was the inline concatenation, so I dim'd a local and assigned the string to it, and passed that to Write. But I have another method that uses inline concatenation that doesn't do this.
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Nov 25, 2009
I have created a calendar in VB which works fine when set to the startup form, but when I use the MdiParent form as the startup form and try to display the calendar by use of a control it just shows all the buttons and labels with no values assigned to them. Its almost as if the Calendar_Load event is not working, or not accessing the methods in my CalendarClass.
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Oct 20, 2010
I am running a website for a F1 racing game, where users can submit their laptimes and compete with each other for the fastest time.
I am now trying to have my website create an image of the top-5 users every... 5 minutes or something, and copy it to the webserver somewhere I can link to. This way the image under that link will update with the latest information every 5 minutes.
To layout the times (these also include the position (1 to 5), the username, the platform, the time of course, and some more details) I am using a DataGridView. I could take the long route and layout the specific 'columns' manually, but I thought using a grid was far easier. I simply set some properties of the grid to make it look nothing like a grid (basically hide the column and row headers and grid lines and give everything the same backcolor). Then I load the times into the grid, and take an image of it using the Control.DrawToBitmap method.
This works fine, but it returns the entire grid. This is a problem because I made the grid extremely large (5000x5000) so that it can always accommodate the times regardless of the length of the usernames. So, the image I get is 5000 pixels wide while it only contains data in the first 500 px orso.
I am currently using the GetRowDisplayRectangle and GetColumnDisplayRectangle methods to figure out the part of the grid that actually displays the times, and use that to cut the image down to the portion I need.
But here's a problem: these methods only return something when the grid is on a form that is currently being shown! I am already giving the grid a parent form (even though I am just creating it in memory and it doesn't need to be displayed anywhere) because otherwise the data wouldn't load, but I was never showing that form. Now it turns out I do need to show the form, very briefly, in order to figure out the area that I need to take a snapshot from.
Remember that this is all happening on a webserver, so I'm not absolutely sure if this is a problem. Is it ok for a webserver to have a form popping up and down every 5 minutes? Or will this cause problems? I honestly don't know but I don't think it's a good thing. Moreover, it also pops up on my own machine when I'm testing, and it's damn annoying.
So my question is basically twofold:
1. Maybe I should ask this in the ASP.NET forum, but is it a problem to show a form briefly every 5 minutes?
2. Is there any other way to get these Get...DisplayRectangle methods to work without having the grid on a physically visible form?
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Jun 3, 2011
I'm trying to make a form in which you would fill in information and then press a "Build" button and it would build another with the information in it so when you open it, it has all the info.
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Jun 5, 2011
I am here with the same Query but with a different look I want to apply the culture change to my program. I created a class library for culture change. and applied it . It is only working with the form name, i did it with two different languages and got the result. But the controls inside the form remains as it is.
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Sep 4, 2009
i have a form with a webbrowser in it, now below is the code i use to generate my context menu, however it only works on the form NOT over the web browser, that has its own right click menu. is there a way to disable the browsers right click and have my own work over the whole form? [Code]
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Sep 5, 2011
how do i populate an array with all the controls of a form and their respective properties?
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Feb 25, 2009
I am trying to build up a login form for my database. I have two fileds Username and password and two buttons Login and change password. I want the change password button to get enabled only if the user enters a default password set by me and the button should remain disabled otherwise.
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Jan 16, 2012
I have been given a VB project by a collegue to import into visualstudio professional to add a setup project to. The project was originally a 2003 projet I don't konw which version, VB express 2003 possibly, then imported into vb express 2008 and now professional 2010.
The problem is every time I rebuild the project without doing anything else the main form changes its size. It shrinks in height by about 40. hit build again and it shrinks again.
what this might be and can it be fixed or will I have to create a brand new project and import the source files with all the risk that that entails.
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Mar 3, 2010
I'm trying to build an application to monitor a site to build statistics from the data being read. This HTML looks like this.
<div id="history">
<h4>HISTORY</h4>
<table border="0" cellspacing="0" cellpadding="0">
[code]...
Now I can read the html and put the text anywhere, I just don't how to read specific parts so I can separate the data out.
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Apr 15, 2012
I am doing form validation in VB, I validate the text field data by using txtName_LostFocus function, and on wrong input I used txtName.Focus(). It works well for me. But problem is that as for as, user does not input valid text, my EXIT button also does not works.
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