Handling Database And Class
Jan 8, 2009
I haven't done any programming in a while, and I have pretty much 0 experience with databases, so I'm hoping I can get some guidance with what I'm trying to achieve.I have a class (or want to have) which represents a person, for each person there's multiple dates, and for each date there's multiple events which have properties like time, place, duty, etc. I want to be able to save and load this from a database using a form. I want it to be able to function where I can type in the person's name and it will load all the data into the form, which has a combo box for the different dates and events, and when I select a different date and/or event I want the data to change correspondingly.
If someone could just give me a push in the right direction as to where I should be looking for help in achieving that I would really appreciate it. I don't have the class made to do any of that, just an idea of how it will function. I haven't worked much with classes, so I'm not sure how to approach it. Meaning I need guidance with classes and databases alike.
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Dec 1, 2011
I have an event defined and firing in class B
Public myEvent()
In class A:
Private WithEvents _b as B
Private Sub hander() Handles _b.myEvent
but, this handler does not get called.
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Jul 6, 2010
Basically, I have a custom child form class which has events that will be passed to the parent. In the custom child form, I have a declaration of a "MustInherit" class that inherits the DevExpress User Control Class.
The reason for this, is I have many user controls that derive from this base class, and the child form can have an instance of any one of these controls, and doesnt care which. The only requirement is that the child form can handle the same events from each type of control the same way.
Some watered down code snippets(still pretty long unfortunately):
'''Inherited Class
Public Class ChildControlInheritedClass
[Code].....
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Jan 10, 2012
We are developing an application for our shop floor. This program will be tracking material through the shop and we need to capture any errors the program generates, but we don't need to stop the program for all errors. I have some code to do a screen capture and put it in a database with exception.tostring data for debugging.
What we would like to do, is create an exception from the base class, but provide additional properties to allow us to set a severity and a user friendly error message. I would like to encapsulate this in a class that we would call in the catch of a try/catch, set the properties on the class, have the class record the data to the database, then raise the exception to the main program to display only the user friendly message and severity. The main program would then determine the severity and based on the severity stop the program or just display a discreet msg and continue to process.
Does anyone have an example of a custom exception class derived from exception that does something similar, or if I heading in the wrong direction, does anyone have a better solution?
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Aug 13, 2009
I already read a lot about exception handling and saw many different threads on the subject but still confused when creating class libraries like the following scenario.
Lets say i have a class library "MyClass.dll", inside the project i have two classes:
Skeleton.vb
Imports System.IO
Public Class Skeleton
Public Function Create(ByVal resourceName As String) As String
[Code].....
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Jul 24, 2010
I have a custom class which basically manages the program settings.
In it's New() event, I'm performing a check to see whether a value stored in My.Settings is the same as the default value (I made sure the value wasn't!), if not then it will perform a RaiseEvent ValueChanged().
On my form, I have an instance of the class declared "Private Withevents ProgramSettings as New clsProgramSettings", I also have a handler "Private Sub DoSomething() Handles ProgramSettings.ValueChanged" declared.
When I run the program the form gets loaded, the instance is created, the RaiseEvent is called, but the handler is not receiving the event?
I tried "Private Withevents ProgramSettings as clsProgramSettings", then creating the instance in the Form.Load(), but still no success!?
Is there something I'm doing wrong, or is there a problem with the IDE? I'm using VS 2010.
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Feb 4, 2010
'I am trying to create a public class for handling stored procedures
'Class declarations
'1) Mode (delete, insert, edit)
'2) Stored procedure Name (sp_insert_MyTable, sp_delete_MyTable)
'3) Stored Procedure Parameter Count ( 10 or 5 depends) (need to avoid this)
'4) Stored Procedure Parameters (Here I need to declare as Structure, use dynamic array)
'5) How I can call this in Form
'My Study Code, Please correct it...
Public Class clsTest
Public Structure spParameters
Public varPara As String
Public varDataType As String
Public varDatatypeSize As Integer
[Code] .....
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Aug 26, 2010
I'm relatively new to VB.NET and am having a problem when Databinding a Class to a Forms Controls. Basically within the Class, when Setting certain String Properties I heck that they are not Null/Empty and if they are Throw an Exception. The problem occurs when I bind the properties to textboxes - when the textbox is empty I expect an error to occur (which I will handle). So does anyone have any insight or solutions into why the exceptions are not being thrown when a textbox changed to an empty string?
A condensed example follows:
Dim a As New SomeClass("Random", "Text")
Dim f As New SomeForm(a)
[code].....
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Jun 8, 2010
i created a Class library (.dll) and loaded it as reference into a main project. In the code for the class i've handled exceptions using try..catch subs, however when debugging the main project exceptions that are handled in the DLL still get thrown! (the class ".vb" file gets loaded into the debugger and the line of the exception shows up)
Up till now i've found it useful that when an unhandled error occurs in the imported reference, it shows up in the main project with tracing back to the referenced class. But i dont want the exceptions that are handled in the reference class to be thrown when debugging the main project!
As you can see the exception thrown was handled with try...catch this class exception.vb belongs to the project that created the class library (.DLL that i referenced). i didnt even load the project that built the reference so it amazes me that it could find the coding class to begin with.
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Sep 28, 2011
I am writing a class library that envelopes an USB device driver. This device has its own class library, provided by the hardware vendor.
Very often, especially if you handle with old DLL or COM assemblies, there are methods (functions to be correct) that return TRUE if all was OK, or FALSE if any error happen. Often these methods return information about the error in one of their parameters or separately in a GetLastError method or even if in an OnError event.
Now, normally I handle all native .NET exceptions in my class libray handling locally or re-throwing to the client if the error is useful to know. But what to do with all other errors that are hidden in the vendor's methods? (in the true I have no exceptions, but only returned TRUE or FALSE values).
Let's make an example with the method "CONNECT" that connect the client to the USB device.
I envelope the method in this way:
Public Sub Connect()
oVendorDevice.connect()
End Sub
now if any connection error happen, the vendor's connect method return FALSE. But I do not know why the connection failed. To know why the connection failed I have to call (for example) the method GetLastError that gives me information about the error. (but do not forget that other vendors use other strategies like returning the error in a method's parameter or in a OnError events.
Now, in order to follow a good .NET exception handling strategy I could write something like this:
Public Sub Connect()
Dim res As Boolean = oVendorDevice.connect()
If res = False Then
[Code].....
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May 30, 2012
I have admin module. This module have one master page which has the no of panels at left side. I have to make this panels visible and invisible with base control class which is constructed in VB language. I'm working with asp.net 2.0 with c# web site.
how do i construct this base control class and manage panels with Master Page on link button click event.
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Mar 14, 2010
I would like to build a base class for my SQL Data Access Layer. I have most of it based out, but have a question about how to handle errors within the base class. I have a method for ExecuteNonQuery, ExecuteReader, ect...
[Code]...
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Apr 16, 2010
I need some basic assistance understanding how to mess with bytes. And when I say basic, I mean dumb it down for me, I'm a self taught hobbiest mostly and only spent 4 years proffessionally in development. And that 4 years was a database programmer handling the connecting, retreiving and inserting of data into various databases.
I can't honestly think of the last time I had to do anything with Bytes, but I do know that when I did, all of the functions that actually did anything were written by someone else. So start off, I've been trying to handle them like strings, and that's not working for me (you probably guessed that).
[Code]...
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Jan 20, 2012
I have a text file contains delimited records.
1243;jhhf';982u4k;9u2349;huf8
kij;9238u;98ur23;jfwf;03i24
I need to replace the value of 4th part of every record with the value returned from SQL database (Select X from T where C='4Th part from the flatfile').
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Mar 4, 2011
I want to handle errors that might occur when user tries to connect to database. I don't know how to do that.This is my connection string used all over the program:
Using connection As New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + txtFilePath.Text + ";Jet OLEDB:Database Password=" + txtFilePassword.Text + ";")
There are a few errors that i faced them myself:
[code].....
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Apr 17, 2012
Here's my current set-up:
Public Interface IDatabase
Function CreateParameter(name as String, dbType as <dbTypeEnumeration>)
End Interface
[Code]....
The problem here is what exactly is dbTypeEnumeration. In the example above, it's simply a placeholder to what my problem is. Since we use both Oracle and SQL Server databases, the DbTypes are different depending on the database being used. For Oracle, the OracleClient object has its own OracleDbType enumeration with types. SQL Server also has its own enumeration.
My question is: is it possible to show those database-specific enumerations depending on which repository is injected into the DatabaseService constructor? If not, what's the best way to go about this? I want to separate the two databases, share logic, and allow for future development, ala the interface as a code contract for that development.
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Oct 9, 2011
I have the following defined in my "Form1":So that I can access all my database functions anywhere in the main form (database connection is initialized via the "private sub new()" function in the DatabaseManager class.The works fine for all queries done in form1, however I have many other classes I'd like to be able to access the database from.Does anyone know how to access the initiated class in my example? Since right now it is initiated in the main form, if I try to access any functions inside any ot
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Sep 13, 2010
I know I'm missing something really simple here, but I'm trying to create a class that I can use to access the database in my program as this is obviously used a lot throught out the program and on different forms. I've used classes for other purposes and never had a problem but for what ever reason I can't seem to get this one to work.[code]...
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Nov 17, 2009
can dot net generate class from database table ? means if i have a 1 table & want to create class for 1 table like insert, update, delete functions & properties(for table columns)
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May 17, 2012
Here is a class to SQL use an access database:
Class MyDB
Public DBName As String
Private con As New OleDbConnection(ConStr)
[code]....
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Jun 13, 2010
Is there a direct way of generating a class from a record in the database?I use a program to edit records and would like to use a class that has the record fields as member for saving the last values entered while adding new records and the initial values of the fields for editing so that if i press ESC the control while editing the value returns to the original.I tried to use dim r as datarow but i get the error that there is no object
and if i declare dim r as new datarow i get the error that new is not implemented.Do I have to write the class definition explicitly?
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Feb 6, 2010
I was hoping that I could get some guidance from some of you guys on Object Design with Database back ends. I am trying to build what could be considered to be my first full scale application, which is a student tracker (simplification). While I have a reasonable idea of how I would go about designing the classes for the system, the bit that I don't know how to do is, how I would go about getting the data to and from the database.
For example with my other applications, I have done a couple of things;
1) Gathered all the data when the application started up, creating the objects then. Then when the application closed sending the data back to the database.
2) Have the code which deals with getting the data in the specific class, so the student class for example would take only one constructor argument which would be the studentID, then the class code would connect to the database and populate the object fields as appropriate.
3) Variations of the above. I have also looked into LINQ, which seems like it would be very useful if you don't expect your classes to deal with any business logic and just data, but I suppose it would be possible to create a wrapper class that would include the business logic.
[Code]....
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Mar 11, 2010
I was hoping that I could get some guidance from some of you guys on Object Design with Database back ends.I am trying to build what could be considered to be my first full scale application, which is a student tracker (simplification). While I have a reasonable idea of how I would go about designing the classes for the system, the bit that I don't know how to do is, how I would go about getting the data to and from the database
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Dec 16, 2009
If Class X is within the scope of Class Y, is X a subclass of Y?If Class A is a sub Class of B, then is Class B considered a super class of A?if Class C inherits Class D is Class D a superclass or parent of Class C?if Class E extends Class F then we can consider Class E a child of F?if Class G inherits Class H and is within the scope of Class I then who is the parent of Class G? Classes that inherits Class J and classes that are within Class J are all sub classes of Class J?
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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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Mar 30, 2010
I've got a fairly large VB.NET (3.5) project that makes a lot of database calls. So I created a namespace/class just to handle those fuctions. The idea was that this single point of entry into the database would give more control over validating input from users.
So my class looks something like this. (I've chopped some code out for readability, it works just fine except for all the open connections.
[Code]...
So I can close the data reader, but how do I reach back to that original database class and close the connection. If I close it in that original class it will bomb when I try to loop through the data reader the in calling class.I'm sure this is probably pretty obvious but I'm fried from the keyboard.
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Mar 7, 2009
code for creating a class in vb.net for a database table that includes insert,delete,update function.
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Jan 20, 2010
i just like to know how create a base class for connecting the database.just the simple one.
what are the best practice in creating a base class connection.
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Mar 2, 2012
I have a class that represents the table of a db-row. Its properties are the columns of the table. I add a new row to the table with the following code:
Public Sub AddRow(oTestRow As TestRow)
Dim sql As String
With oTestRow
[Code]....
That is just an example, but my classes have around 30-40 properties and this brings a very large and complex sql string. Creating, editing or maintaining these sql strings for many classes could generate errors. I am wondering if any compact way or method exists in order to add the whole object's istance (the properties of course) to the table "TestTable" without writing such a large sql string. I created the TestRow in the way that its properties are exactly the columns of the table "TestTable" (with the same name). But I did not found in the ADO.NET anything that could be used.
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Oct 27, 2010
I am working on designing a SQL Server database connection class in VB.net 2005. The idea behind doing this will be so a developer can can call the class, pass it a stored procedure name along with the parameters, and get return values back (if any).
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