Hi I am developing a WinForms app which is using LocalDb with EF for data access.
So far the db access in my WinForms app was performed only once at a time, just by calling:
using (var context = new EfDbContext())
{
// do something on context entities
}
when needed.
Now I am facing a new requirement - I need to create an extra background service which will be used to periodically get the data from files located on some FTP servers, and then - update / insert the new data within this SQL LocalDb.
What I would like to achieve is to grant simultaneous access to the SQL LocalDb data for both WinForms app and this new background app (service), so that it would be possible for the user to view data from Db (in WinForm app), while an update of the data is performed in the background (by the service).
I would like to ommit the resources blocking for each other.
Can that be done (and how to do that)?
Thanks!
UPDATE: I forgot to mention that the data sets which will be read from ftp files and then inserted into database may be quite large ~20-50k of records, each record consist of decimal field, DateTimeOffset field, and few Int32 fields.
Just use it and don't worry for now about concurrency. SQL Server widely used in highly concurrent applications like ASP.NET Web Apps and your example isn't so special. Blocking can be a problem when using transactions with write operations. But there are many Transaction isolation levels to solve this problem and it's irrelevant for now for your task I think
Related
I have a WPF application that:
Takes user input, stores it into a database
Reads from a database and displays it on the screen
Currently is just using SqlConnection method to execute and query a SQL Server database
When deployed, this application will have multiple within network users that should be able to connect to the application and read/write to it as well. Of course, this database is user access controlled, and the end users don't have access to the SQL Server instance. The only ways I can think of connecting are:
Using a generic account that has access to the database and then including that in the connection string.
Creating a REST API to pass requests to the database, bit unsure on details.
What would be the best way to go about this?
REST API would add a level of complexity and additional infrastructure requirements to your application. It would also add an opportunity to use the application outside your network, so that may be a plus. However, if that's not the anticipated use case, it's probably overkill
Also, REST would still need an account to access the database, so it's not really better than your first idea. Depending on the WPF part, you may also have to change the access to the data (for example, using web service clients instead of EF).
Perhaps you can add your users to the database and give them limited privileges to only access selected tables, views or stored procedures. This can add a fine grained control of who and what on the database level. However, this requires a bit or lot of work, depending on the number of your users.
So, your first idea is the easiest one and can probably be expanded to the separate database accounts for your users, while REST probably requires a bit of additional work and setting up the web server etc.
I want to make a background running desktop app using asp.net c#.
The idea is to check a local database table and get all data from that table in order to insert all those data in live database table.
If there is any better solution for that scenario please suggest me one.
It seems that what you want to solve is moving data from multiple local databases into a central one so you can consume it via an asp.net website.
I won't be discussing application part since that's an easy problem to solve once you can connect to a db that has all the data you need.
There are several things to consider here:
Recurrence (one time migration vs continuous synchronization)
Direction (do you need to sync one-way from local to central or two-way)
Data Contract (do local databases have same or different schema than central database)
The Data Contract is your biggest problem if schemas are different since you will need to design at least a target schema for the central database that can take in data from local dbs.
Even if schemas are identical, you will need to devise a way that data is partitioned in central database, you might need to introduce a sourceDatabaseId column in your tables so you won't have conflicting primary keys (you won't have this problems if your primary keys are guids)
The others can be solved either building:
A windows service - Inputs: periodicity (e.g. every hour), source db and target db connection strings. You will have a main loop that waits until time to run has come (based on periodicity) and fetches data from source db and saves them into target db (preferably in batches)
A console application - Inputs: source db and target db connection strings. You will just move data in batches. You can configure a Scheduled Task on the server that will perform scheduled runs of your console application to solve the periodic running part.
You would set up one such windows service or scheduled console app per local database.
If you have complex databases you can look into tools like Microsoft Sync Framework to perform this data synchronization.
you can develop a windows service to do this type of work and install on server with timer setting.
I'm very new to .NET, C# and SQL Server.
I need to develop a socket application using C#. That application should insert, delete, update, etc the data in database with respect to some request.
I need to develop another windows service application using C# that sends the data in the database to the web application through http.
The both applications run in the same system. The database is SQL Server. Both the applications use the same database.
I am unsure if while one application is deleting or inserting data in the database, then is the other application still able to access the database at a same time.
Sql Server can handle multiple requests just fine. Each connected client gets a different spid.
However, it is up to your sql server code (batches or sprocs) to handle data conceurrency issues via isolation levels and transactions. So in order to control one user reading data while others are updating, deleting etc..., you need to use isolation levels and locks.
Isolation levels:
http://msdn.microsoft.com/en-us/library/aa213034(v=sql.80).aspx
Also: http://dbalink.wordpress.com/2008/05/27/isolation-levels-and-locks-in-sql-server-2005/
Good writeup on transactions:
https://web.archive.org/web/20210614153200/http://aspnet.4guysfromrolla.com/articles/072705-1.aspx
I think that the simple answer is yes - multiple applications/people can access a database at the same time.
You may want to read up on transactions within a database and concurrency:
http://en.wikipedia.org/wiki/Atomicity_(database_systems)
http://msdn.microsoft.com/en-us/library/cs6hb8k4(v=vs.80).aspx
It is possible to access the same sql server database by as many applications as you want. If you are afraid that one application can attempt to read the data being changed by another one at the same time, read about transactions and isolation. But in very short, if you make a small atomic change which requires one line of sql code only, you probably shouldn't care about this at the moment.
My client application maintains Access database and most of time work offline.
In server side there is a web service with Oracle back end. I need to update Access database row data tables with latest Oracle database table data. Currently I'm doing this by C# windows service which triggered by timer. Is there any alternative to achieve this data synchronization with fault tolerance and good performance. Please share your experience.
Quartz.NET (is a full-featured, open source job scheduling system that can be used from smallest apps to large scale enterprise systems.) to schedule synchronization.
Data base synchronization can be done using Microsoft Sync Framework but I'm not sure whether it support for Access database or not.
I have a datalogging application (c#/.net) that logs data to a SQLite database. This database is written to constantly while the application is running. It is also possible for the database to be archived and a new database created once the size of the SQLite database reaches a predefined size.
I'm writing a web application for reporting on the data. My web setup is c#/.Net with a SQL Server. Clients will be able to see their own data gathered online from their instance of my application.
For test purposes, to upload the data to test with I've written a rough and dirty application which basically reads from the SQLite DB and then injects the data into the SQL Server using SQL - I run the application once to populate the SQL Server DB online.
My application is written in c# and is modular so I could add a process that periodically checks the SQLite DB then transfer new data in batches to my SQL Server.
My question is, if I wanted to continually synchronise the client side SQLLite database (s) with my server as the application is datalogging what would the best way of going about this be?
Is there any technology/strategy I should be looking into employing here? Any recommended techniques?
Several options come to mind. You can add a timestamp to each table that you want to copy from and then select rows written after the last update. This is fast and will work if you archive the database and start with an empty one.
You can also journal your updates for each table into an XML string that describes the changes and store that into a new table that is treated as a queue.
You could take a look at the Sync Framework. How complex is the schema that you're looking to sync up & is it only one-way or does data need to come back down?
As a simply solution I'd look at exporting data in some delimited format and then using bcp/BULK INSERT to pull it in to your central server.
Might want to investigate concept of Log Shipping
There exists a open source project on Github also available on Nuget. It is called SyncWinR, it implements the Sync Framework Toolkit to enabled synchronization with WinRT or Windows Phone 8 and SQLite.
You can access the project from https://github.com/Mimetis/SyncWinRT.