Generics - Create A Common Database Class In .NET?
Jun 12, 2009
We have 3 databases providers we use to connect to our databases: DB2, MS SQL, and Interbase. I would like to create a single generic database wrapper class that can be used to talk to all three just by passing in the correct connection string, username, password, and the provider desired.
I don't want to have to add references and import all three providers in the database class. Is this possible?I have done this before in Java using the Class.forName() function.
Public MustInherit Class Entity(Of T As Entity(Of T))
And various classes derived from it. I would like to have another class accept all of the derived objects as a property, but I cannot seeem to find a workable syntax. If it were a parameter of a sub, I could say
Public Sub Foo(T As Entity(Of T))(TheEntity As T)
I can't seem to get that to work for a property:
Public Property E(Of Entity(Of T))() As Entity(Of T)
Gives me "Type parameters cannot be specified on this declaration"
Public Property E() As Entity2008(Of T)
Gives me "Type Parameter T does not inherit from or implement the constraint type ..."Is there an acceptable way to do this or am I stuck with using a Set Sub and a Get Function?
So I implemented my own form of Enum static classes so I can associate strings to enumeration values. One of the shared functions in each enum class, GetValue, is used to quickly look up the string value from an internal array via the offset. While all of the enum classes implement the same exact function, the data types of their parameters differ, specific to the enums in each class.
So I come to a point where I want to create a generic class that can use any of the enums by passing it as a generic type parameter. But I cannot find a way to constrain type T in such a way to be able to call each enum's GetValue function. This is where an interface would come in handy, but VB.NET forbids interfaces for shared methods.
I have a base class that I could constrain to, but the base class doesn't implement the GetValue method, and I can't define a generic version of it, because I need to rely on shared properties of each child class in order for GetValue to do its thing.[code]..
I have some common code that I would like to share between pages and I have been messing around with App_Code classes which is great but I would also like to use code that affects drop down lists example:
Sub Set_FirmType(ByVal Sender As Object, ByVal E As EventArgs) subcategories.Visible = "false" supplycategories.Visible = "false"
I have got the list of Class Name as Follows: Type[] typelist = typeof(Sample.Students).Assembly.GetTypes();
Now i have complete list of all classes available in Sample NameSpace:
Now i want to get data through class I am using Devexpress Persistance class so basically i have to create XPQuert Object as follows: XPQuery<Employee> EmployeeQuery = new XPQuery<Employees>(XPODefault.Session);
But in my case Employee class will be listed in typelist variable..How can i create the object of XPQuery.. is it possible something like this: XPQuery<typeof(typelist[0].Name)> EMployeeQuery = new XPQuery<typeof(typelist.Name)> (XPODefault.Session);
I am trying to minimize my code writing. I have DBLayer base class that selects, inserts, updates and deletes records from database. I need only fieldlist and table name from each derived classes to perform the actions. I have defined static tablename, fieldnames in derived class. Currently I am defining next static functions in derived class for GeneralSelect [which selects all records], GeneralInsert[Which inserts a records], GeneralUpdate[Which updates records as per given id] and GeneralDelete[Which deletes a record of the given id]. The parameter and all functioning are same just the differece is the table name and fieldnames.
One DBLayer Class that performs database actions Class DBLayer Public shared function Query(byval SQL as string) as dataTable
[code]....
... same goes for all other table objects... If I have 20 database tables i have to write getdata method in all 20 class changing only the tablename so i would like to get ride of it. So in order to get ride of it what do i need to do?
I happen to have these common procedures which I want to be used in my forms and usercontrols, with the form I can put those procedures in the base form which is being inherited but I happen to have a need to use those same procedures in my usercontrols, is there a way that I can have a common base class that I can use both for my form and usercontrol? I haven't used yet a base usercontrol since my usercontrols will not look the same so I have to put those procedures in each one of them and I find it rather cumbersome.
Can I use tools commonly for all the winforms? How to create common toolstrip? For example : I have one toolstrip.it has one delete button. All winform has one datagrid and data comes from differs tables. Now I want to remove the data from the any datagrid all winforms.
I have to create an XML database for a class I'm taking, but I'm running into some problems. I'm trying to pack my data directly into the DOM using some classes I created and derived from the XMLDocument class, I'm trying to do it this way so I can easily manipulate the entries while the document is in memory and save them back to a file without having to mess around too deeply with the XMLDocument class. I'm running into some problems however when I try to typecast the elements I get from calling
Code:
XMLDocument.DocumentElement.Item
I assume that this is happening due to my derived class not being pushed into the DOM when a file is loaded, because it works just fine if I enter the data manually in code.
Code: Option Explicit On
[CODE].............
Other than writing my own XMLReader I have no idea how to accomplish this, does anyone have an idea how I could go around doing this(other than writing my own XMLReader).
I need some expert help in achieving this task. I have an xml file which will be emailed to me everyday. I need to loop through the xml and create tables in a database based on the xml nodes and their attributes. looking at the following xml fragment for example: Code:
So based on the above xml, I would have to create a Shipment table as a Parent with fields like ShipmentIdentifier. Then I would have to create an Event table with the ShipmentID as a foreign key and fields like Source, Code. Basically a field for each node. Then if there are columns in the table that are new, I would have to modify the table and add the column. I only have to create tables where there are child nodes or where the nodes have attributes.
I want to create a class (I think) that has properties that correspond to column names in a database table, such that they come up in Intellisense when I type the dot after the class name. Is this possible to do?
i saw more applications can run in more than one systems and accessing a common database whenever update a data from one computer thats reflects in another eg a product is select by one system in a shop it wont showed by another system in the same local network.how to develop that kind of apps what kind of applications they are .please explain about that concept or give some ebook references.give me a simple vb application code in vb.net like above mentioned.[code]
how to implement UI, BL and DAL in a project the way that I see it as a requirement for some projects. The way I am able to do a project now is from a form create an object of a class in which there are properties and functions that do database selects, updates and deletes. Looks to me that doing a project like that is separating the UI from the DAL. In an update button click event I may call Obj. Delete (txtCustID.txt) for example. I don't understand the part of further breaking it down to include a Business layer; in which a vb solution is made up of three solutions.What goes in the BL?Does the BL call the DAL?
I have data entries in my database that have a common field. For example:
account_id type user_id
1 new 1 2 old 3 3 new 1 4 old 1
I am using a query like this(mysql): SELECT account_id, type, user_id FROM table WHERE user_id = 1
This is just all theoretical. The problem that I am having with this is it is only returning the first result in this case account_id 1. How can I get it to find all the results with the user_id 1 because in the way I am thinking that it is failing is that it is finding only the first result and then ending?
This was an experiment to see if I could create a fake array using generics instead of using an array. I decided to try it, because I may use it if I find any advantages to using it over an array. it works, I am just asking for a second or third opinion, have I screwed anything up, or is there an easier way to accomplish this? If I use it, it will be for a 2D game I am creating, and is used to draw the 2D screen graphics, placing an image based on what image identifier is located at what coordinates. The value stored in the fake array is an integer that disignates the graphic to draw and whether it is passible or not, i.e. 0 = a floor image, 501 = a wall image that is impassible (any image number > 500 is impassable) The Class definition:
It is possible to create windows service using windows form control in vb.net. give me the url or links. The windows forms control such as, Timer control, list-box, notify-icon control etc.
I've been creating short test apps repeatedly to try to understand some of the concepts in VB.NET.For the most part it has been illuminating.I read Bucky's .NET knowlegebase tutorial on passing objects as parameters to newly created forms. He shows how to create a new class that inherits from the base form class and define a New() method with parameters Extending the concept I thought about doing the same thing with a form that was created at design-time (In this case Form2).
I want to read a number of items from a file and then associate each of those items with a new button at run-time, so that when the user clicks one of the buttons I can display some information about that item.Can I use a LIST to manage these buttons and items? Can I create a new class and have each list item of that class, such as 'btnID', 'btnText', etc... ?
I want to create a class that will "search" for something. Basically I load up the "search item" when the class is created and inside the class is logic to do the "search". The result of this logic will be more "searches" that I want to start. How can I have the logic in the class create another instance of the class itself?
I'm in the process of trying to create a class that will allow me to create windows shortcut; Im using the following PDF file that gives me the shortcut file structure.
Ive been able to successfully load a shortcut file and parse its Lnk File Structure but now Im on the Shell Item ID List structure but I cannot find the Structure of the ITEMIDLIST anywhere
Furthermore I know I could use the Windows script object, but this is a dependency Im trying to avoid if I can, hence writing my own Shortcut class.
I'm try to create a class has been create by main class only by protect sub New but how do I create it ?
Public MustInherit Class Rune Protected MustOverride Function Create() As Rune Public Shared Function Factory(Of T As Rune)() As T 'I can't use "T As {Rune, New}" because Sub New isn't Public 'Return (New T).Create End Function End Class
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
In my program I have an interface iGraphable that contains two properties: Abscissa and Ordinate. Then I have an xxxx class (actually more than one) implementing iGraphable and a ListOfxxxx class implementing BindingListView(Of xxxx).To draw graphs I have a Graph class with a property called Data whose type is BindingListView(of iGraphable).Why have I a cast exception when I pass a BindingListView(Of xxxx) to the Data property.
