I made an application that generates reports based on data from a database.
The functionality of my application is correct, but I have a following problem: my client has 2 identical databases - one for testing and one for actual work he does.
My application should work with both databases (it should have a "switching mechanism"), but I don't know how to implement it.
I know that I could just switch between connection strings but the problem is that in my reports I use datasets that are bound to one database.
Is it possible to fill those datasets with the data from both databases (since the databases are identical in schema, it should be possible), and how would that be done, or do I have to use duplicate dataset/report pairs?
I'm using C# in VS 2010 with SQL Server 2005, and .rdlc for my reports.
Thanks.
Ideally you should should be able to change the connection string in one place and it should affect project-wide.
This will work ONLY IF you get the connection string from one place. Keep it in the app.config file.
See this article to see how you can store and read the connection string from the app.config file.
You've hit upon the reason why people implement the Repository pattern or at least a version of it.
You really need to remove your business logic away from the database, so that it is database agnostic. It shouldn't care where the data comes from only what it is.
From what you' said the implication is that your client doesn't wants more than just a change in the app.config connection string used for database access.
If that is so then, I know that it will entail some work, your best bet is to have a singleton pattern type class to control all data access to and from your data layer.
Using a known inteface you can use a factory pattern to create access to your development or live database at runtime (perhaps based on an app.config setting or even a test class that has no database access at all, but just returns hard coded test data.
Related
I am current building (in C#) a fairly basic point-of-sale program for a local community in Uganda to use in tracking business at their sunflower seed press. I was thinking that I would need some sort of database (like a SQL database), but I've never set up a database before, so I'm wondering what the best way to do this is. Maybe a database isn't the best way. The program will not have internet access, so everything will have to be done locally on the machine.
I think your first step should be designing out what data you need to store. Build an Entity Relationship Model and decide what your domain model is going to be. There are many different Database Engines out there that you can use that have different features, installation requirements, etc. A database engine can be installed locally, or on a remote machine to connect to. If you're writing a C# app, you'll probably want to use the System.Data namespace. You can use plain ADO .NET, or use something like Linq To Enttiies to help create proxy classes for your data tables.
You can access a SQL database using the same API for queries / record extraction regardless of the DB Engine uses. In some caess, you may need to use a seperate library that provides an implementation (or a better one), as in the case of an Oracle Database and the Oracle Data Access Components. Right out of the gate, .NET works very well with Microsoft SQL Server, but other options would work.
The details of what database engine are not as important as defining a good set of data tables to represent your data.
Yes. If it has lots of data you have to consider using database. Whether you have internet or not, as long as you have local network, you can easily do database.
Set up a database server ( maybe sql)
Do your database and install it on the database server
Do your application and connect to your database through connection string.
You are on the right track to use a database to store data. It is pretty easy to accomplish. Your computer does not need to be connected to the internet.
SQL Server Express Edition is free with a limit of 10 gigs of data. This will probably be much, much more space than you will need.
From C#, use ADO.NET. It is very simple if you know some SQL. Code samples here.
I ran into real brick wall trying to connect to dynamic databases. And I don't know how to achieve this,
Here is my process, I have an application where it needs to be adaptable to changes in the work environment, say If the work places server crashes and they create a new database with the name db_new the application would connect to that instead of the old database name.
I already have a window that displays the databases from the server on a listbox where the user can specify which database to use for the application. But the issue is, how can I save the selected database name so that it can run after the new database is selected? ..
as in the administrator should be able to change the database the application uses if necessary and the application should keep on using that selected database till the administrator changes it back to a new one.
Please forgive if the question a bit vague, I just put it together in the best way I could, any help on this would be really great :)
EDIT:
And I cannot use text files or xml s as the database name the application uses should be stored in a secure manner. :)
First of all, you can very easily use a text or XML file: If you store the information in a file, that can't be downloaded by the user (as I assume you would), this is as safe as it can be: If somebody manages to break into the server and read the file, it's game over anyway.
That said, I would recommend you use MySQL proxy or a similar mechanism and point your WebApp at it - failing over to another database or changing the underlying database could then be handled at the proxy layer without the WebApp even knowing about it: The functionality need not be part of your application and in my book it shouldn't.
You haven't told us the language you are using. Therefore we cannot offer very good suggestions.
My first thoughts:
If this was PHP you could have the general app use something along the lines of,
$db->execute('sql statement here');
and then just have the administrator change the current $db when needed. That way $db->execute() will always be executed on the "current" database.
Edit: This should still work in C#. If you have the functions using the database call a variable that is the current db connection then you should be able to change the db connection to the proper database whenever you need while the rest of it continues running since it's just the same variable.
Our company inherited some software that runs on C# Visual Studio 2010, Windows 7 and Oracle 11g. After some effort we got the software working and got a stable database (schema) set up.
We are now starting the process of migrating some data from an old system to this "new" system. However, I don't want to mess up our working schema as I expect a bit of trial and error work will be needed with our data import.
I wanted to do the following:
Let's say our existing schema is called PROD. I wanted to create a second schema called TEST that we can use for the imported data. Then, in the C# code I can just switch the name of the datasource when switching between our two database schemas. The catch is that the username and password for this connection appears in a multitude of places scattered in the code. To avoid having to change user credentials in multiple places every time we switch between "db environments", I wanted to create a single user to have access to PROD and to TEST.
However, how to grant user privilege on specific schema? suggests this is not possible. Correct way to give users access to additional schemas in Oracle suggests a method for granting access on an object level, but this is insufficient: I basically want one single user to have access to two identical schemas (PROD and TEST). Once I've achieved this, I want to start modifying TEST to start with our data import.
I have also tried creating TEST as a separate Oracle Database installation on a different port, but when trying to create my user on this new instance I still get a conflict that the user already exists (since it was created for PROD in the original database installation).
My user already exists and has access to PROD. How do I give him access to TEST as well? Or how would one solve the more general problem of having a PROD and TEST database defined in an application that uses Oracle?
In MySQL this would be trivial, but I don't have any idea how to do this in Oracle. I am very new to Oracle.
The question of giving permissions has already been answered.
Now to your question, as a whole: Am I reading correctly that you want to update the database schema, but you want to keep it in the same database as another schema and run both in what appears to be a production database? If so, read that again to let it sink in how extremely dangerous that is.
When migrating from one "schema" to another, as a software update, it is safer to create a new database and migrate the data. This gives you plenty of shots, as you can blow away the new database as you tweak scripts.
If you want as little friction as possible in your software, you need to do a couple of things:
Refactor out the code from the moron who decided to hard code connection information in multiple places. You need to get the strings in one place and make sure you extract out the Data access layer (DAL) code into its own class.
Consider creating domain objects that do not rely on the database schema(s). I consider this mandatory, but you could get away without doing this. I would still create domain objects, even if they match the PROD schema tables, as you should not be using data constructs if you are moving from one schema to another.
Create an interface for your data access layer (DAL)
Map the current data schema, through the current DAL, to the domain objects, using the interface.
Map the new schema, through a new DAL, to the domain objects, using the interface.
Create a factory (or use the provider pattern) to determine which DAL object you are going to use (this makes the application configurable to old or new "schema"
I'm assuming that you have a schema PROD and a DBUSER which have some privileges to objects in this schema.
DBUSER's name and password is hardcoded all over the application.
You've created a new schema TEST which looks the same as PROD (including grants to DBUSER).
You want that wherever the application does something like:
UPDATE some_table set ...
It will update some_table table in TEST and not in PROD.
My suggestion is to use and change SYNONYMS, ie-
When you want to update some_table in PROD, do:
CREATE OR REPLACE PUBLIC SYNONYM some_table for prod.some_table;
and when you want to update some_table in TEST, do:
CREATE OR REPLACE PUBLIC SYNONYM some_table for test.some_table;
The connection to Oracle is not handled correctly in the C# code and this is what is causing difficulty.
If the Data Access Layer were defined separately as Gregory suggests or if a more generic naming convention were used in SQL statements as A.B's answer points to, then it would be much simpler to switch between two databases.
Since our mandate currently doesn't involve making any changes/refactoring of code, I am using a backup and recovery approach:
I create a backup of the working database. Then I do the necessary tests and changes on the database. If I need to revert back to the working database, I create a backup of the "testing" database again and restore the original working database, using the appropriate flag to replace existing tables in the case of a restore. This enables me to switch back and forth between the "working" database and the "test" database.
This is not ideal as it does take some time to execute the backups and restores, but works without affecting the C# code and gives the ability to do work on a "testing" database without affecting the working one. Since this is a temporary scenario until the "testing" database becomes working, this is the approach I'll be following.
As the other answers point out - there is a more generic need to fix/refactor/generalize the connection code - I believe that is the best approach and the only reason I'm not doing that immediately is because we are not yet mandated to change the code.
I have probably written the same LINQ to SQL statement 4-5 times across multiple projects. I don't even want to have to paste it. We use DBML files combined with Repository classes. I would like to share the same Library across multiple projects, but I also want to easily update it and ensure it doesn't break any of the projects. What is a good way to do this? It is OK if I have to change my approach, I do not need to be married to LINQ to SQL and DBML.
We have both console apps and MVC web apps accessing the database with their own flavor of the DBML, and there have been times when a major DB update has broken them.
Also, since currently each project accesses the DB from itself, which is sometimes on another server, etc. Would it be possible to eliminate the DB layer from being within each project all together? It might help the problem above and be better for security and data integrity if I could manage all the database access through a centralized application that my other applications could use directly rather than calling the database directly.
Any ideas?
The way I handle this is using WCF Data Services. I have my data models and services in one project and host this on IIS. My other projects (whatever they may be) simply add a service reference to the URI and then access data it needs over the wire. My database stuff happens all on the service, my individual projects don't touch the database at all - they don't even know a database exists.
It's working out pretty well but there are a few "gotchas" with WCF. You can even create "WebGet" methods to expose commonly used methods via the service.
Let me know if you want to see some example code :-)
I want to create a GUI with C++ (QT4). The GUI should work on Windows and should be able to
create a database
use the database created by it (I should use an existing DBMS, in order not to worry for queries)
database should be specific to the GUI, other software should not be able to use that database (the database may be for example encoded)
the gui with its ability of working with database should be easily installed on the other computers, that is I don't won't to ask user to change some options on his computer manually
So my questions are:
What kind of database can help me to do this, what I should learn connected with database to be able to perform this task?
Should I encode the database by my GUI, or databases have such command to save them on disk already encoded?
Thanks!
You could try looking into SQLite. The library can be used with C++. It will not need an external DBMS. SQLite is embedded into your application, and you can access you database through it. Also, the database files it produces can be encoded, so it will be accessible to your application only.
first, you should decide what are the scenario your system going to be applied.
then only proceed to source for database provider (MySQL, Postgres, etc).
you can't really jump to UI implementation straight away because all of the database mentioned above can do what you need.