Class Variables - Holding Data From SQL Server Query
Oct 1, 2009
I am creating an ASP.Net page with VB.Net codebehind. I am using a class variable to hold data (named ods see below) from a SQL Server query so I do not have to keep going back out to the server. The class variable gets loaded ok and I populate a grid data with this dataset. However when I need to go back in and reference the dataset again, I get an error and I come to find out my dataset no longer holds the data.
Here is my declaration in my code behind:
Partial Public
Class LotTrackingMain
Inherits System.Web.UI.Page
Private con
As SqlConnection =
Nothing
Private ods
As
New DataSet
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Oct 1, 2011
I am trying to use several Class arrays to hold values that I will cycle through at a later point to perform some calculations. I need to change the array sizes to fit the data as it is entered. I am using one procedure to set the first element of each array and then a separate procedure to pass the additional values as they are entered.
Until my last attempt at changing my code, my StartBalance sub seemed to work, I could step through and see the values assigned to the class arrays in the code block. However, when it moved on to the Transaction sub, it did not recognize that the first set of values were set, the array shows zero values for index 1.
I have gone through several changes trying different ideas from reading blogs and articles, but I guess I am not understanding how these work. I even used the class arrays directly instead of the Property procedures to see if I would get a different result, but I do not.
I believe I must be approaching this incorrectly and though I can find dozens of examples of setting class variables and even a couple on using arrays as class variable, I can not find any that show how to then pass values to those arrays.
Public Class Statement
Private _tranDate(1) As Date
Private _amount(1) As Double
[Code]....
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Mar 23, 2012
I define some global variables of a class as follows:
Private Class MyClass
Private var1 as Decimal
Private list1 as List(Of string)[code].....
But I found that after this form is closed, all above variables, var1, list1, list2 still exist in memory. I thought they should be collected by gc since the form is already disposed as I confirmed.
Add: I have monitored half an hour after the form is closed. But these variables are not collected by gc. I have an automatic update procedure on the form which uses above variables.Since the above variables still hold values, the automatic update procedure is always called which causes exception. (One quick fix is to check if form.isDisposed in update procedure. But I do not think this is elegeant. Besides, these variables occupy memory.)
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Nov 23, 2011
At the moment I am using Access & an OleDb connection to store data. I went down this route originally because I though that this was the best way for applications that I am distributing to my clients.
I would prefer to use something like SQL Server but is this a good idea for software I am distributing? Does the average Joe's PC have SQL Server pre-installed? If not, I suppose I can provide them with a link to download it for free?
Is there any better alternatives to Access / SQL Server?
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Jun 9, 2012
I'm new in .NET programming.I have a class Form1 that includes Button1_Click event.Button1_Click creates a multiple Text Boxies at run time)Here is the class:
Public Class Form1
Dim shiftDown As Integer
Dim counter As Integer
[code].....
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Jun 14, 2009
I wrote a procedure that builds a DataTable in memory using data stored on our DB2 database. The function builds a Multi-Level Bill of Materials (BoM), meaning that the data cannot simply be queried. The function works great and returns a nicely arranged DataTable object. However, I then need to query the in-memory DataTable against other tables on our server. What would be the best way to approach this problem? Should I make a DataTableAdapter for the Server tables and then build a DataView? I don't have too much experience yet with Data objects. (By the way, I looked into LINQ to DB2 and even installed IBM's addin's, but our server doesn't seem to support it at this time.)
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Feb 16, 2012
INSERT INTO [ET_SolutionText]
([SolnTextKey]
,[SolnTextValue]
,[SolnTextTitle])
[code]....
In Above Query, SolnTextValue is XML field. How i can format XML data in Values using insert query in SQL server 2008?
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May 28, 2009
Need a SQL Server "SQLClient" (VB) Data Layer Class?
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Jan 12, 2011
Ok, I want to create a class that will handle a special rectangle graphic.In my form, I want to have two of these special rectangles. So, basically, I need two instances of that class in my form, right?I manage to initialize two, alright. But, how exactly am I supposed tomanage drawing/graphics etc in a class, and the results to be displayed in my form?
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Dec 27, 2010
I am trying to use an Asynchronous HTTPListener to create a simple web server in VB .Net (Not ASP) This will be run as a desktop application. My only goal is to be able to request Server Variables from the client. Is there any way to do this from within a HTTPListenerWebServer? I am using the code from the MSDN VB .Net Samples:
[Code]...
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Aug 12, 2008
I have a DataGridView of which is being populated via a table adaptor.
I can populate it with a query where the value is statically assigned in the query.
What I'd like is a textbox where I can type in a variable for the query and then populate the datagridview.
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Nov 19, 2010
I have two forms and I'm trying to pass a declared variable from form1 to form2 and then pass that variable in a sql query that I have in a dataset that is bound to my form. I know that my query works but it's not producing any data. I have debugged my form and can see the data being passed in the variables elsewhere on the page but I'm not sure of the syntax within the query.
[Code]...
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Feb 18, 2009
I'm having issues w/ querying the database w/ user selected dates. Hardcoded everything worked fine but when I started to use the DateTimePicker things stopped working.
Dim sqlcn As New SqlConnection(db.dbcn)
Dim cmd As SqlCommand = sqlcn.CreateCommand()
cmd.CommandText = "SELECT * FROM TABLE " _
& "WHERE CHK_DT BETWEEN @BeginDt and @EndDt"
[Code]...
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Dec 20, 2010
I am wondering how to replace two variables in a query from selections that the user makes. One variable is chosen by a combo box called cboYEARMONTH and the other is selected from a list view called employeeListView. I know that I can use .replace to insert the YearMonth into the string but, how do I also replace the EmployeeID in the query string?
[Code]...
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Mar 15, 2012
I am finding it exceptionally difficult to pass an sql query result (string) into a variable.No matter what I try, I can't seem to get anything but boolean output from my reader function.I need to obtain staff "account type" from my staff table and then define that account type in a variable.
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Apr 26, 2011
I added queries to my dataset via the designer. Is there a way to use variables in those queries?
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Mar 30, 2012
This is my first attempt at writing a program that accesses a database from scratch, rather than simply modifying my company's existing programs. It's also my first time using VB.Net 2010, as our other programs are written in VB6 and VB.NET 2003. We're using SQL Server 2000 but should be upgrading to 2008 soon, if that's relevant.I can successfully connect to the database and pull data via query and assign, for instance, the results to a combobox, such as here:
[Code]...
How do I execute a query so as to assign each field of the returned row to individual variables?
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Apr 22, 2010
Basically i have a query string that when i hardcode in the catalogue value its fine. when I try adding it via a variable it just doesn't pick it up.This works:
Dim WaspConnection As New SqlConnection("Data Source=JURA;Initial Catalog=WaspTrackAsset_NROI;User id=" & ConfigurationManager.AppSettings("WASPDBUserName") & ";Password='" & ConfigurationManager.AppSettings("WASPDBPassword").ToString & "';")
This doesn't:
Public Sub GetWASPAcr()
connection.Open()
Dim dt As New DataTable()
Dim username As String = HttpContext.Current.User.Identity.Name
[code]....
When I debug the catalog is empty in the query string but the WASP variable holds the value "WaspTrackAsset_NROI"
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Dec 29, 2010
In my program I have a combo box that the user selects a date from and a list view that the user selects an employee ID from. How do I properly design my database query string to use both the date selected and the employee ID selected? The date is stored in a variable called YearMonth and the employee ID is stored in a variable called EmpID.
Here is what I am trying to do with my query:
Dim ExactQuery As String = _
"SELECT * " & _
"FROM[JobTypeExact_Query] WHERE (EMPID = ?) AND WHERE (YEARMONTH = YM)" 'Define Exact job type query
[code]....
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Jun 4, 2010
I am trying to add shared members in derived classes and use that values in base classes...
I have base
class DBLayer
public shared function GetDetail(byval UIN as integer)
dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin)
end function
end class
[Code]..
currently there is error using the tablename variable of derived class in base class but i want to use it i dun know other techniques if other solutions are better then u can post it or u can say how can i make it work? confused...
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Oct 18, 2011
I have some variables in my main Form, but I want them in all my other forms, how can I make them kinda global or something?
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Mar 5, 2010
What's the proper way to declare variables in a class? I've been doing something like:
'in a class
public shared teststring As String = "first"
'on a code behind
[Code]....
with shared variables loading a second window or reloading the page (without clicking the button) renders the hello world string. so how do I declare variables in a class but make it per instance?
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Sep 23, 2011
Background: I am working on an ASP.net project that basically fills out a form from user input. The generated form (for reasons which I have no control over) must be a JPEG or TIFF. So the user fills out the web form, which takes all of the input values and meges them into a blank image (jpeg) of the form. Using System.Drawing, it merges all of the text onto the form at designated Points. The points are defined as variables which are modified at runtime to compensate for the resolution of the image (in case it get modified/re-generated at a different dpi). All of this is working fine.
Problem: Currently I have a Sub that determines the dpi of the master image, then adjusts the Points accordingly. However, there are ~50 variables that have to be adjusted. So currently I have the Sub go thru each point variable and manually adjust the X & Y values. I have been working on a Sub that will iterate thru all of the Point variables and do adjustment. Here's a functional sample of what I have working:Imports System.Drawing
Partial Class test Inherits System.Web.UI.Page
[Code]...
This works...sort of. It allows me to grab each variable and modify it, but only in the instance. The original variable in the class is unchanged. Which means that when the program gets to the point where it's drawing text to the image, the points are unmodified. my basic question is: Is it possible to modify the original variable using this sort of process? If not, is the best way to use these modified values to declare the new class instance at a global level, then have the Sub that draws the text use the instance versions of the variables?
I realize that I could define all of the points in an array which would be easy to loop thru and update, but I've named each point variable something meaningful to correspond to the related text to be drawn.
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Dec 16, 2010
I'm trying to create a generic Controller Class for generic events. But these these events still need to access their class variable. So my idea is to create the Base Controller Class with a ModelBaseclass variable as _ClassVar, which is inherited by all of the other class Controller classes will derive from. But I want the derived controller classes to override the _ClassVar with whichever one they need.
I want to do this, so the ControllerBaseClass can have all the generic functions that all the Derived Classes would use.
Model :
Public Class ModelBaseClass
Public Overridable Function Foo() As String
Return "Name"
[Code].....
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Jul 23, 2009
I am making a small application in which i have added a class module and a window forms in vb.net. i want to acess the shared variables and mathods of class without making any object.
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Jan 28, 2009
I have a class file, myClass.vb. Here is an example of the file:
Private _active As Integer
Private _categoryID As Integer
Property active() As Integer
[code]....
when I want to assign a value to the variables in the class file, should I assign them like what I have in line 24, and 25 or line 28 amd 29? how I assign the variables in terms of performance?
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Feb 25, 2010
when using variables in object names.I have a Public class which is called "Tank".In that class, there is a public property called "direction" of an integer type.I keep getting the error:
"Tank is a type and cannot be used as an expression"What I'm doing wrong here ?
Public Class mainroutines()
Create Instances of tank
Private Tank1 As New Tank()[code]....
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Oct 31, 2011
I have been charged with porting a VB6 project into VB.NET. In vb6, if you were in a class separate to a particular variable, you could access that variable easily:
Public Class Foo
Public k As Integer
End Class
Public Class Bar
k = 12
End Class
In VB.NET, my understanding is that before you can use a variable in another class, you must declare a new instance of it:
Dim foobar As New Foo
This would be fine, but I have to access these variables from different classes and every time I declare a new instance, it wipes all old values from the variables, which I need. I tried using Inherits statements but they presented many problems.
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Jul 7, 2009
In the code below, the namespace is called "Navigation" which I think is correct. Then I have a class called "Heading", which by definition is the direction a person/vehicle is truly pointing towards. I think that is also named correctly. In the code below, I have four things I have named:
_WhatToName1, WhatToName2, WhatToName3, and WhatToName4.
The value that gets passed in and stored is a double between 0 and 360 -- essentially the degree value from a circle. For WhatToName3 and WhatToName4, I have seen a lot of places that just use "value" as the name. Is that standard?
Namespace Navigation
Public Class Heading
Private _WhatToName1 As Double
Public Sub New(ByVal WhatToName3 As Double)
Me.WhatToName2 = WhatToName3
[Code] .....
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Aug 20, 2010
Ok so here's the story. I have an array of Assemblies which are initiated by [Assembly].LoadFrom() that load a number of DLL's. Upon initialising, a method called InitMain (from the DLL!) is called, which sets a number of variables outside of this method, like here:
Public Class Example
Dim C As Integer = 0
Public Sub InitMain()
C = 50
End Sub
[Code]...
If I call the method Test using that same array of Assemblies somewhere later in the main application (like pressing a button or something to trigger it), it will pop up a messagebox with that says: "C = 0"Why is this? Is it fixable without any odd workarounds?
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