Concept of a database driven program in VB.NET - database

Question

I have been developing programs in VB.NET for a few years and am familiar with it. The area where I do not have a lot of exposure is databases.
I am writing a program (for my personal use) called movie manager. It will store information on movies I have. I have selected Sql Server Compact Edition database. Assume I have a database with two tables namely Info and Cast. Info table has a few columns such as movie_name, release_date and so on. Cast table has few cols such as first_name,last_name etc.
Right now I have created a DataSet which reads all the info of tables from database (opens connection, fills tables info, closes connection). This way in a global variable I have a snapshot of database.
My queries :
Once I have data with me, every time I need to add, edit or delete a record I have to open a connection, fire an sql and close the connection. Right ? Is there a way to do this without using Sql ? Plus is this concept okay.
Since I am not using structures so I need to create empty datasets to store temp information. Is this convenient ?
If I have to search for a specific thing in dataset table, then do I have to loop thru all items or can I use sql on dataset or is there an alternate ?

Answer 1

1)Once I have data with me, every time I need to add, edit or delete a record I have to open a connection, fire an sql and close the connection. Right ? Is there a way to do this without using Sql ? Plus is this concept okay.
No. To update a database, you have to use the database. Create a stored procedure in the database to handle your functionality and then call it from the code and pass in whatever data needs saved. DO NOT USE INLINE SQL. Paramterized stored procedures are the way to go.
2) Since I am not using structures so I need to create empty datasets to store temp information. Is this convenient ?
It depends on what you're doing. I would create an object model to retain my updated data and then I'd pass the properties into the stored procedure when it was time to save my changes.
3) If I have to search for a specific thing in dataset table, then do I have to loop thru all items or can I use sql on dataset or is there an alternate ?
You can loop the rows or you can use linq to pull what you need out. Linq is really nice as it's basically .NET coded queries against a collection.
There are plenty of tutorials/guides out there to show you how to update via stored proc call form your code. There are a ton of linq tutorials as well. Basically, a linq query against your table will look something like:
dim result as Generic.List(of String) =
(from r in table.AsEnumerable()
select r
where r["columnName"] = "the value").ToList()
This syntax is probably a bit off, but it looks something like that.
Edit
Your Model:
Public Class EmployeeModel
Public Property Id
Public Property FirstName
Public Property Last Name
Public Property JobCode
Public Sub EmployeeModel(your params)
//set properties
End Sub
End Class
Your DAL:
Public Shared Class EmployeeDAL
Public Shared Sub SaveEmployee(ByRef model as EmployeeModel)
// call your sp_SaveEmployee stored procedure and set the parameters to the model properties
// #id = EmpoyeeModel.Id
// #JobCode = Employee.JobCode
// ...
End Sub
End Class
I use VB every few months, so there are probably some small syntax errors in there. But that's basically all you need to do. The function to save your data is in the DAL, not in the class itself. If you don't want to use a DAL, you can put the save functionality in your class, though. It'll work the same way, it's just not as clearly separated.

Answer 2

On your Questions.
number 1: You have to connect to database in order to store and retrieve data. There are lots of ways on how to deal with it and one way of it is to use app.config or you may simply create a function that calls the connection every time you need it.
number 2: Since you are dealing with dataset here are some tips you might want to look at DataSet
number 3: You can also try using Data Adapter and Data Table. I am not sure what you meant by your question number 3.
Cheers

Answer 3

I have problem with the way you are using your database and the ram of your computer.
Problem1: since you already have a database for holding the movies information why are you again holding the same information in memory?, creating an extra overhead. if your answer is for performance or i have cheap memory then why don't you use xml or flatfile instead? Database is not needed with this senario.
Problem2: You are like a soldier who dosent know about the weapon he use? right? because you are asking silly questions your first question about opening connection.. the answer is yes you have to open the connection every time save/read the data and close it as soon as possible.
your second question about convinent the answer is no. instead create class with all field as property and some method for initialization,saving,deleting. this way you have to write less code. nad suppose you have a movie names xyz there can be another movie xyz how will you distinguish it? if you have whole information b4 you you can do it via release date ,casts etc, but still it will be hard, so create a primary key for both your table
and finally your 3rd question , it will be easier to use use sql queries than looping thru the dataset(get rid of the dataset as soon as possible)
wish yu good luck on the road to rdbms