.net - Sharing Mdb Access Connection Among Multiple Forms?
Sep 7, 2010
I'm starting to put in a database into my application, however I'm drawing a blank on how to share a database connection among the dozen or so different forms in my MDI application. I'm assuming this has to do with interfaces or something but I can't find any relevant examples anywhere. Can someone help me out? Ideally what I'd like is when the app is loaded up there is a call to a function in the forms loading area which establishes a single connection to the mdb, that I can then call via any form so I don't always have to open/close connections everytime I need to update the db?
Here's a basic example of the mdb database access code I've got working:
Dim dt As DataTable = New DataTable()
Dim OleDbTran As OleDbTransaction = Nothing
Using connJET As OleDbConnection = New OleDbConnection("connection string here...")
1) I am writing an application for a touchscreen which will have several different Forms - each of which will be full-screen. What is the best way to achieve this? Hide/show each Form as the user navigates between screens? MDI Parent with multiple Child Forms becoming visible 'on top'? Or is there a more elegant solution?
2) I would also like a 'banner' on the top of each Form (or always visible on the top of the MDI Parent, etc) similar to a 'navigation frame' on a website. This banner will display a clock with the current time, and the current GPS location (meaning that a Timer will be used to get/set these values every 1000 milliseconds). I thought of using a UserControl for the banner - but if this is used on multiple Forms then I will end-up with multiple Timers all waiting 1000 milliseconds to update essentially the same information.
Is there a best practice for this type of scenario? - my thoughts so far are using the "Main" Form for Global Timers, etc - but then how do I update all Form clocks each second? (without iterating through all visible Forms... which seems messy).
I am using Synclock to prevent multiple threads from logging text messages to the same file at the same time, but this doesn't seem to work:I get frequent sharing errors on the logfile, within the synclock block.The Synclock is using the variable holding the filename, because it exists all the time and because it is always the same object, whatever class instance or thread I'm in.[code]Despite using Synclock and a Using block around the code, I keep getting this error in the sw.WriteLine(Msg) line:System.IO.IOException: The process cannot access the file '(filename)' because it is being used by another process.Should I use some other type of object than a string to synchronize on?I cannot use a user interface object (button or so) because it is a windows service project.It was written and compiled in Visual Studio 2008, but targeting the 2.0 framework because it has to be able to run on some old Win2000 machines.
I'm testing database programming in vb.NET 2008 at the moment and try to find a way to use a database connection in different forms, so e.g. I put the the database-connection-component into one of the forms. I know, I could access it by e.g. form1.databaseconnection.xxx, but is this the best way or can I "put" the connection into something more abstract which all forms know about?
I have a VB Solution with a dozen forms trying to implement invoice system.My main form (Say Form1) only has a design to create , Edit or Delete Customers.My form 2 will be opened if Create button is clicked. In my form 2, I have textboxes where user can enter Customer details and click on SAVE. My doubt is here....On clicking this SAVE button in Form 2, I want a INSERT command to happen on the MSAccess's Database table called Customer (which I have already created... this table does not have any records as of now). In my form 1, I added a MSAccess Database with a Connection String. In my Form1's code I have code like this[code]...I got this piece of code from this link [1]: vb.net - sharing mdb access connection among multiple forms/Now, I do not know what more code does this require to INSERT records from my text box into the Customer table's fields.
My question is, am I able to share a business logic layer seemlessly between the two presentation layers or is there anything I need to watch out for. I'd really like to not have any duplication of business logic, so any advice would be more than welcome.
I have an application built that has several forms. I use an XML file to store settings data (mainly folder names for data output) and I need each form to be able to access and modify the data. I'd also like each form to access functions from a main form (such as file parsing functions). I have read articles about properties and inheritance but I need some guidance as this topic is pretty confusing.
I know a little about threading and delegates, as well as socket programming. I'm working with a VB.NET-compatible SDK called TrueVision3D to create a small online game for me and my friends. The problem is that I cannot for the life of me figure out how to pass data from one thread to another. I've created 2 seperate threads on seperate forms.
The first thread is created on a form titled FrmLogin, and it contains all the socket code. I need to be able to update variables in the second thread, which mainly consists of a render loop. The second thread is created on a form titled FrmMain. I'm not quite sure if it matters what forms the threads are created on, I'm just trying to give as much information about the issue as I can. I've tried using delegates and events to pass information from the thread back to the form it was created on, which works fine, but how do I pass data to the second thread from the first?
I have an application that needs to perform a series of different actions at specific points in time.To do this I have a timer with various actions that occur in its tick event.One possible action is to send out a few messages via a serial port and then wait (between 1- 300 mins typically) for the next timer tick.Another possible action is to continuously toggle one of the control lines on the serial port until the next tick (again 1-300 mins).
In most instances, i'm happy for everything to run on the main thread, but in the case of toggling the line endlessly, I thought it better to give it its own thread.My problem is that for the new thread to use the Serial Port, it must open the port. Likewise, it must close it before the main thread can have it back.
Here are 2 code snippets
Private Sub activityTimer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles activityTimer.Tick Dim some variables here activityTimer.Stop() If speedThread.ThreadState = ThreadState.Running Then
I have the following code... in an MDI application. [code] Various lines of code which put data into the Myinstance and then save the instance into the ArrayList.I have buttons which run procedures and functions in the formchild and also in the Class1. I need it so you can jump between formchild instances, and when you do so and click a button on that form, it will run the Class1 code but using the data in the arraylist and myinstance that was set previously by the selected formchild. Then if you switch to another child it uses data from this form. Can this be done by declaring the arraylist with more dimensions and then refer to the records with the index of the selected form instance, e.g.Selected Child is index(3)
I have created an MDIparent form and a MDIchild. There is a button on the parent which makes multiple 'clones' of the child form, each time its clicked.I also want (maybe with a module) a set of variables, and array of a structure but these are available to each copy of the child, but each copy's variables, arraylist etc contain its own data?Therefore if you select child1 the variables and array will have different data to child2, child3...etc...
I am working with several RFID readers that perform different function in my vb.net program. Currently each reader port number is hard coded into the respective form. For example, reader 3 operates on COM1. However, this will be problematic when installing on different machines.
What I would like to do is have a "configuration" form where the user can select each reader and then select the COM port. Then all other code references these settings. What would be the best approach for this.
The only way I know to do it currently is to place this information in a small database and then have the forms reference that database, but it is a lot to do for such a seemingly trivial task.
I have some icons and images that are stored as embedded resources in my form1.resx file. Is there any way I can access these resources from my Form2 without adding the icons as project resources?
How do I share text between forms?I want a box to popup exactly like a input box, but needs to be multiline, Is there any east way to do this or will I have to create a second form?If so, how do I share the string between forms to then output in a textbox on 1st form?
Also, I have VB 2008 Standard, and I want to build an application for a handheld, Is it possible to build an application and then pass it over to someone who has the professional version to make it work on pocket pc? Or does the entire build have to be on pro already?It's a very simple program...
I am trying to figure out how to seperate my business logic from my forms. This is my first attempt at doing this, but I would like to figure out how to handle events from multiple forms within a class. I have found myself routinely writing the same logic over and over in each form class and its time I figure out how to completly seperate out that logic in winforms so I can reuse the methods across all of my forms.
So basically I have this click event in form1: Private Sub btnSubmit_Click(sender As System.Object, e As System.EventArgs) Handles btnSubmit.Click
When I declare a variable as public, shouldn't it be available in another form? I am trying to write a windows mobile prg with 12 static mileage points, form1 has the 12 buttons for start point, but when I call form2 with the destination points, my start variable value is not carried over. I intend to then assign a mileage based on the two points and write to file on mobile device. We support 12 schools, and I want my employees to track mileage easily.
Public Class main Public start As String = "start" Public dest As String = "dest" Public miles As Decimal = 0 [Code] .....
i've almost completed my Yahtzee game except for the high scores function. I've got everything worked out except how to take the highscore variable from Form1, and share the data with Form 2
I have a windows forms application with one exe and several dlls(Class libraries) in a single solution. The application uses common data that is used across all the dlls. I would like to load the data when the application is starting up and use the loaded data at various points in the dlls so that I do not have to load the common data again and again. How can I share the data loaded in main EXE across the DLLs?
I need to share variables across two forms in vb.net. One of them is the main form and the other is a child form.
Create a static/shared variable in one of the forms and access it in the other forms via: Form1 frm = new Form1(); //creating object of parent to access shared variable frm.a = "abc"; // passing value
Send an instance of the main form to the child form when creating the child form. The variables can then be accessed via a property function. Create global variables in a module. This seems like the easiest option, but I doubt it is the best option.I also read something about delegates and events, but I don't know how to implement this.
I have a form that can spawn a child form, something like:[code]I want to be able to launch multiple children. Unfortunately, I seem to be getting conflicts within the controls of the children. One button will run the other child's control, etc. They also seem to think that their class-level variables are accessible to each other. Private Shared variables like the following are conflicting (one form thinks it's seeing the other form's "mp3file" variable as their own):[code]How do I spawn children forms that keep their controls and data separate?
I have two forms A and B. B is a child of A - i.e. I have a button on A that pops up form B. I want B to be able to access and change data (e.g. an instance of an object etc.) in A and also to call some function in A. At the same time I'd like to preserve the right to alter the data in A without opening B. I've achieved this using the following (i.e. by declaring the object and method as Friend):
Public Class frmA Friend _data as Hashtable Friend Sub GetData() If _data IsNot Nothing Then _data As New Hashtable
Is there anything inherently wrong with the what I've done and if so how can I achieve a similar result? (It seems to work - I can read, add to and change the values in the _data Hashtable from within form B and when B is closed the values persist i.e. I can access the changed values from within form A. I just dont know if its a horrible fudge).
I am sharing databinding when opening a detail form a summary form. The data is shared fine. What I don't know is how to save any data that may have changed, or to create a new record.[code]...
I have a very simple 2D array, it holds a list of song titles, their genre, and their runtime. frmMain loads the array from a text file and allows me to manipulate it and boil it down to a desired (implicitly sized) playlist. i want to THEN pass that playlist array to a second form, frmPlaylist The problem i'm running into....When frmPLaylist calls the Property from frmMain I receive an error that VB cannot convert the string value to a two dimensional array. Simplified...frmPlaylist is all locked and ready to receive a 2D array, but frmMain seems to only be sending a single string variable. on frmMain
Public ReadOnly Property PlaylistOut() As String Get Return mstrTimedPlaylist(,)
Am new to VB, can anyone tell me very simple how to share the MAIN Bindingsource with an detail form where i want to edit 1 record from the main datasource? andreg
I want to add a close button to a custom navigator. That's fine.
Now what if I want to use it on every form that I would create ? What is the best way (Is subclassing possible for this control in that case, ...) ? Any inspiring code somewhere even for another type of control ?
I want 2 forms the main form which is form1.vb and the second form which is form2.vb to share the same value:
Dim Name As String="App1" so i can use it by simple doing that: [Form1.vb] Public Class Form1
[Code].....
Or it could be better if i didnt have to add a reference to the main form the string Name should be already declared in the second form so i could use just:
I have the requirement to create an application that has multiple front ends developed using Windows Forms, WPF, ASP and Compact Framework Mobile Forms.I would like to be able to create a series of obejct representing the business logic and have this logic accessible from the various front ends available. My first thought was to use remoting as I'd like to be able to pass the business objects back and forth between client and server but the compact framework doesn't support remoting and also transferring a full framework business object to a compact framework business object doesn't seem possible.My next thought was to use web services but again the passing of business objects seems to be very hard to accomplish. Without doing this I would have to create individual web methods for each business operation.
Finally my next option is to use sockets and write the whole client/server logic within some classes and expose them to the UI/Business layer. My only problem with this is it is not scaleable should the number of clients increase dramatically whereas using remoting or web services I can host the solution via ASP.Net.Does anybody have an ideas on the best way forward for this or even have any input on how they would write an application that required a windows form, wpf, asp website and mobile device GUI all of which want to use the same business logic?
I have googled high and low to find an answer to this but I must be searching wrong.I have an application which has a listview displaying some items that are stored in a SQL Compact database. I am using a second form to add new items to this list directly into the database.When the second form closes I want to call the sub in my first form to refresh the list from the database.
How can I get it to fire the form1 sub routine on the close event of form2
i was doing a fair amount of programming many years ago, like 10 it feels like, so I'm sorely not up to date on how my newly downloaded Visual Basic Express expects me to communicate with it.I am writing a program that pulls a cell from a database after the user has gone through several forms to determine which cells they want. When I write it like that, it doesn't sound very efficient, but I've designed it this way for usability.Here's where I have a problem: Should I store the path the user takes in a string, an array, what?
Here's an example:Someone wants baseball stats and trivia. They run my program, main form pops up, they select National League button, the NL Form pops up. Now the way my program is set up right now, is there are two ListBoxes on the form, one is populated, and as the user selects a Team from ListBox1, it jumps to ListBox2. Once they've selected all the teams they want info for, they click a button Next.
What I now need the program to do is show the next form "Team: name" once for each team, and insert the name of the team on the form in the appropriate label which I'll have blank. This form will also do the Listbox thing except the first listbox will populated with Topics like HR Stats, Pitching Stats, Coach History, etc.
