I'm not sure if this is possible and I can't find any answers anywhere else.
Is it possible to have a blank OleDb database stored in the Folders of a Project in C# and after a buttonClick replace the current database (that's being used) with the blank Database?
I'm not looking for a way to save the data from the original somewhere else, although I can understand how that is useful and good practice.
I'm primarily interested in whether this is possible, and how I would go about learning how to use it in my system.
Thanks for reading, and thanks in advance for any help or suggestions :)
I suggest instead of using a fixed database file the user has to "reset", allowing the user to create multiple database files that he can choose from. Most office applications have "create file"/"open file"-dialogs, so users are very familiar with them. You may want to implement an "open last file" or "recent files list"-feature for convenience.
First of all, this would allow the user to start fresh without having to throw away his old data. A user would also be much less reluctant to create something new than to "reset" something (as he should be), so that would also help in user experience terms.
Secondly, disconnecting a database or truncating the contents can work, but it is not as simple as it first sounds. If you're still connected to the database, the file will be locked and you can't remove it. The truncate approach can also cause problems, not only does your whole application have to be able to deal with a suddenly empty database, existing foreign key constraints will have to be considered too.
Related
I am trying to build a WinForms app that allows the user to fill out a form for our company while keeping it clean and standardized. As part of this project, I have created a replication from our production Db with only the tables for clients and client contacts. I need those tables available to the App so it can pull current client information for this form. I wanted to add another table to the replication that is not from the original Db that will take all the information added for the form. I guess I don't need it, but I was wondering if it was possible and, if so, will it break anything.
I can already hear some of you guys reading this saying, why don't you just add another table to the production Db. Well, I thought of that but, the App that is bound by that Db is very strict and runs a check every time the app is launched to make sure the Db hasn't been corrupted. If it finds a new table has been added, I'm sure it wouldn't work. Also, I hear some of you shouting at your monitors, "Why do you want this table as part of the Replication, Why not just house it on a different Db that won't affect your precious app?" And to those people I would say, I just thought of that. But, I am trying to make something lightweight that can be put on a lot of computers without much over head or back end. Thank you in advance for considering this problem.
I am designing a WPF desktop application and using Entity framework Code First to create and use SQL Server Database. My database will be hosted on One Server machine and will be running 24*7.
I want to provide a feature, where you can modify data offline(when you have no connectivity with SQL Server DB) and Save it somehow. And whenever your application will find connection with SQL Server, all changes can be moved to SQL Server DB.
Is there any way to achieve this by using Entity Framework ?
I want to emphasis on the part that I am using Entity Framework. Is this type of functionality already implemented by EF?? Or I have to do it manually, like have to write that in any file system and then manually merge it later to DB ?
You could figure out the specific exceptions that are generated when the SQL Server connection is lost, and embed your calls in try-catch blocks. If the server is offline, then in your catch block, pass the entity to a method that serializes the entity to JSON and saves it to the hard drive in a special directory or something. On your next successful query, check that directory to see if there are any saved entities that need to be saved.
Be specific with your catches - you don't want unrelated exceptions to trigger this code.
Some things to keep in mind - what if somebody else changed the data in the meantime? Are you intending to overwrite those changes? How did you get the data which needs to be saved in the first place if you are offline?
As long as you have all data loaded into DbContext/ObjectContext you're free to amend those data anyway you want. Only when SaveChanges() is invoked, the connection is really needed.
However, if you're going to load everything into the context, you seem to reimplementing DataSet functionality, which, in addition, allows for xml serialization/deserialization of the changes, so the changes can be even saved between sessions.
Not as trendy as EF, though :)
While I have never tried this with SQL-based data I have done it in the past with filesystem-based data and it's a major can of worms.
First, you have to have some means of indicating what data needs to be stored locally so that it will be available when you're offline. This will need to be updated either all the time or before you head out--and that can involve a lot of data transfer.
Second, once you're back online there's a lot of conflict resolution that must be done. If there's a realistic chance that someone else might have changed the data while you were out you need some way of detecting the conflict and prompting the user as to what to do in that situation. This almost certainly requires a system that keeps a detailed edit trail on every unit of data that could reasonably be updated.
In my situation I was very fortunate in that it was virtually certain that if the remote user edited file [x] that overwriting the system copy was the right thing to do. Remote users would only be carrying the files that pertained to their projects, conflicts should never happen. Thus the writeback was simply based on timestamps, nothing more. Data which people in the field would not normally need to modify was handled by not even looking at it, modified files were simply copied from the system to the laptop.
This leaves the middle step--saving the pending writes. I disagree with Elemental Pete's answer in this regard--simply serializing them and saving the result them does not work because what happens when you read that data back in again? You see the old copy, not the changed copy!
My approach to this was a local store of all relevant data that was accessed exactly like the main system data was, all reads and writes worked normally.
Something a lot fancier might be needed if you have data that needs transactions involved.
Note that we also hit a nasty human problem: the update process took several minutes (note: >10y ago) simply analyzing what needed to be done, not counting any actual copy time. The result was people bypassing it when they thought they could. Sometimes they thought wrong, oops!
just a quick question that I am sure someone on here can give me a detailed answer about.
Basically, I am using a DataGridView to display records from a database, which in my case is simply a text file which is being parsed. I feel this is simple, and if I want to select records based on certain parameters, I iterate through the list searching for matches. However, I wonder if this is ineffective vs using a full blown DB such as Mongo or SQL.
Can I get away with this if my software is relatively simple? I really prefer to sway from complicating things, when they don't need to be complicated.
By the way, I am expecting to have a DB (sometimes) larger than 100k entries, so take that into consideration.
#DavidStampher
Even though you may be using just one table or file, I would strongly suggest using a database system for this. Database engines are optimized for speed so it's not so frustrating or time-consuming when performing via query versus trying to update a single text file.
I'm only suggesting MySQL as an option because it's the one I am most familiar with. Other users may have different or better suggestions.
You can easily download and install one from MySQL installer. The setup is relatively simple and should take less than 10 minutes. You could create a new schema, add a table, then query up to do what you need.
I would suggest creating a new user other than root, just in case someone manages to hack into your account.
If you would like the easiest way to manage the database rather than going through the old fashioned phpMyAdmin, download MySQL Workbench. It's pretty cool and relatively easy to use.
Let me know if you have questions. :-)
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.
I'm working on a program that needs a feature that has similar functionality as a contact list. I need to have user settings, but I don't know how, if it's even possible, to create application settings in code.
I would like to be able to add as many new "contact" settings as needed, so I figured if I couldn't create new settings, I should just have one setting that is a list, but that also doesn't seem to be possible. I've looked around on here and Google and can't find anything to fit my needs.
Requirements:
Store contact-like data such as phone numbers, email addresses, etc.
Be able to add as many of these contact settings as needed.
Everything in one executable file.
Edit: So there's the object data type, which seems to fit my needs. Is there a reason this wasn't an answer to any of the very similar questions to mine? It seems to be perfect..
Edit: Nevermind, seems to be compiler errors when trying to access a property of my object because it doesn't have that property until it's an instance of my own objects...
With JayP. Sql Server Compact might also be a possibility, it creates a local 'mini' database, without the need of a sql server installation.
While it is pedantic, I'm not sure a contact list should really be considered as 'settings'. It's really data. As such, it might be better to store this data in an XML file or similar.
Let me add my 2 coins. The data the #Walkerneo is talking about is not "settings" data. It's real data that should be considered in other way. I would suggest to separate them into 2 parts: real data and real settings.
The best place for real data is DB. It may be Firebird or MS SQL Compact or something else.
As for settings the Registry is a good place. At least Qt that is cross platform language uses this approach for Win apps
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