Hey guys I'm new to C# and I'm a little confused on the fields that need to be provided in the connection string while using oledb to connect to my sql server 2008 database, particularly one of them.
The "Provider" field is really giving me problems, partially because I'm not really sure what it does. I have tried two different Provider strings and they both come back with the same error:
The "System.Data.SqlClient provider is not registered on the local machine
Or
The "Microsoft.Jet.OLEDB.4.0" provider is not registered on the local machine
Can someone tell me what this means? Also, my task requires me to not use any addition installations, is there a provider that is default?
Thanks
The Microsoft Jet Engine is the database engine used in Microsoft Access. The error simply means that the required Access version is not installed and thus, your application cannot open the OLEDB driver.
Generally, you should probably just use the System.Data.SqlClient.SqlConnection class instead of the System.Data.OleDb.OleDbConnection class to connect to your SQL Server 2008 database. The connection string should be much simpler.
Related
How can I use my LocalDB on other computers?
SqlConnection connection = new SqlConnection(#"Data Source=(LocalDB)\v.11.0;AttachDbFilename=[DataDirectory]\Database1.mdf;Integrated Security=True");
I tried this but it doesn't work because I get this error:
Local Database Runtime error occurred. Cannot create an automatic instance
Does someone know how to fix this, or what I can do instead?
I don't want to use SQLServer because I am making a program for an offline computer.
The fact that your app is for an offline computer is irrelevant. If you're attaching an MDF file on demand then that will only work with a SQL Server instance installed on the local machine anyway.
As suggested elsewhere, LocalDB is intended for development use only. Your users should be installing SQL Server Express and you can specify that in the connection string. If you're going to use a SQL Server data file, i.e. an MDF file, then you need a SQL Server instance to attach it to. If you don't want to have to have a SQL Server instance installed then don't use a SQL Server data file in the first place.
LocalDb is sql server and is only intended for development purposes. It isn't something you would use for distributing an application. SQL Express is an option for you, but may be overkill for what you need. You might look into SQLite as you might find it easier to embed and distribute with your application. Of course, the right answer depends on your actual requirements, etc.
Apparently, using AttachDbFilename and user instance in your connection string is a bad way to connect to a DB. I'm using SQL server express on my local machine and it all seems to work fine. But what's the proper way to connect to SQL server then?
Thanks for your explanation.
Using User Instance means that SQL Server is creating a special copy of that database file for use by your program. If you have two different programs using that same connection string, they get two entirely different copies of the database. This leads to a lot of confusion, as people will test updating data with their program, then connect to a different copy of their database in Management Studio, and complain that their update isn't working. This sends them through a flawed series of wild goose chase steps trying to troubleshoot the wrong problem.
This article goes into more depth about how to use this feature, but heed the very first note: the User Instance feature has been deprecated. In SQL Server 2012, the preferred alternatives are (in this order, IMHO):
Create or attach your database to a real instance of SQL Server. Your connection string will then just need to specify the instance name, the database name, and credentials. There will be no mixup as Management Studio, Visual Studio and your program(s) will all be connecting to a single copy of the database.
Use a container for local development. Here's a great starter video by Anna Hoffman and Anthony Nocentino, and I have some other resources here, here, and here. If you're on an M1 Mac, you won't be able to use a full-blown SQL Server instance, but you can use Azure SQL Edge if you can get by with most SQL Server functionality (the omissions are enumerated here).
Use SqlLocalDb for local development. I believe I pointed you to this article yesterday: "Getting Started with SQL Server 2012 Express LocalDB."
Use SQL Server Compact. I like this option the least because the functionality and syntax is not the same - so it's not necessarily going to provide you with all the functionality you're ultimately going to want to deploy. Compact Edition is also deprecated, so there's that.
Of course if you are using a version < SQL Server 2012, SqlLocalDb is not an option - so you should be creating a real database and using that consistently. I only mention the Compact option for completeness - I think that can be almost as bad an idea as using AttachDbFileName.
EDIT: I've blogged about this here:
Bad Habits : Using AttachDBFileName
In case someone had the problem.
When attaching the database with a connection string containing AttachDBFile
with SQLEXPRESS, I noticed this connection was exclusive to the ASP.NET application that was using the database. The connection did block the access to all other processes on the file level when made with System.Data.SqlClient as provider.
In order to assure the connection to be shareable with other processes
instead use DataBase to specify the database name in your connection string
Example or connection string :
Data Source=.\SQLEXPRESS;DataBase=PlaCliGen;User ID=XXX;password=ZZZ; Connect Timeout=30
,where PlaCliGen is the name (or logical name) by which SQLEXPRESS server knows the database.
By connecting to the data base with AttachDBFile giving the path to the .mdf file
(namely : replacing DataBase = PlacliGen by AttachDBFile = c:\vs\placligen\app_data\placligen.mdf) the File was connected exclusively and no other process could connect to the database.
Apparently, using AttachDbFilename and user instance in your connection string is a bad way to connect to a DB. I'm using SQL server express on my local machine and it all seems to work fine. But what's the proper way to connect to SQL server then?
Thanks for your explanation.
Using User Instance means that SQL Server is creating a special copy of that database file for use by your program. If you have two different programs using that same connection string, they get two entirely different copies of the database. This leads to a lot of confusion, as people will test updating data with their program, then connect to a different copy of their database in Management Studio, and complain that their update isn't working. This sends them through a flawed series of wild goose chase steps trying to troubleshoot the wrong problem.
This article goes into more depth about how to use this feature, but heed the very first note: the User Instance feature has been deprecated. In SQL Server 2012, the preferred alternatives are (in this order, IMHO):
Create or attach your database to a real instance of SQL Server. Your connection string will then just need to specify the instance name, the database name, and credentials. There will be no mixup as Management Studio, Visual Studio and your program(s) will all be connecting to a single copy of the database.
Use a container for local development. Here's a great starter video by Anna Hoffman and Anthony Nocentino, and I have some other resources here, here, and here. If you're on an M1 Mac, you won't be able to use a full-blown SQL Server instance, but you can use Azure SQL Edge if you can get by with most SQL Server functionality (the omissions are enumerated here).
Use SqlLocalDb for local development. I believe I pointed you to this article yesterday: "Getting Started with SQL Server 2012 Express LocalDB."
Use SQL Server Compact. I like this option the least because the functionality and syntax is not the same - so it's not necessarily going to provide you with all the functionality you're ultimately going to want to deploy. Compact Edition is also deprecated, so there's that.
Of course if you are using a version < SQL Server 2012, SqlLocalDb is not an option - so you should be creating a real database and using that consistently. I only mention the Compact option for completeness - I think that can be almost as bad an idea as using AttachDbFileName.
EDIT: I've blogged about this here:
Bad Habits : Using AttachDBFileName
In case someone had the problem.
When attaching the database with a connection string containing AttachDBFile
with SQLEXPRESS, I noticed this connection was exclusive to the ASP.NET application that was using the database. The connection did block the access to all other processes on the file level when made with System.Data.SqlClient as provider.
In order to assure the connection to be shareable with other processes
instead use DataBase to specify the database name in your connection string
Example or connection string :
Data Source=.\SQLEXPRESS;DataBase=PlaCliGen;User ID=XXX;password=ZZZ; Connect Timeout=30
,where PlaCliGen is the name (or logical name) by which SQLEXPRESS server knows the database.
By connecting to the data base with AttachDBFile giving the path to the .mdf file
(namely : replacing DataBase = PlacliGen by AttachDBFile = c:\vs\placligen\app_data\placligen.mdf) the File was connected exclusively and no other process could connect to the database.
Good morning all,
recently I came upon problem with DB connection in Python and C#.
For example, let's say we want to connect SQL Server. In .NET (C#) we just need to know the server name, credentials and we can connect to DB with SqlConnection object. That's clear.
Now, in Python, when using pypyodbc we need to specify driver additionally. And here's come the question:
Why in Python we have to specify driver? We don't have to specify it in C#.
On the other hand, if specifying driver is so crucial, then why don't we have to specify it in C#?
I know, that in C# we have dedicated class for SQL Server (does Python? or pypyodbc is the only choice?), does that mean, that it has some method to resolve which driver to use? Is it the same with Oracle?
I know nothing about python, but I think that should answer your main question:
SqlConnection is designed specifically to work with SQL server, so you don't need to specify the driver, because it uses it's own designated driver.
From SqlConnection.ConnectionString Property page on Microsoft docs:
The ConnectionString is similar to an OLE DB connection string, but is not identical. Unlike OLE DB or ADO, the connection string that is returned is the same as the user-set ConnectionString, minus security information if the Persist Security Info value is set to false (default). The .NET Framework Data Provider for SQL Server does not persist or return the password in a connection string unless you set Persist Security Info to true.
(Emphasis mine, other stuff in the quot are just to provide context.)
And later on down the page:
The .NET Framework Data Provider for SQL Server uses its own protocol to communicate with SQL Server. Therefore, it does not support the use of an ODBC data source name (DSN) when connecting to SQL Server because it does not add an ODBC layer.
(again, emphasis mine.)
When working with other connection classes such as OdbcConnection or OleDbConnection, you need to specify the driver in the connection string.
With Odbc Connection Strings use the keyword Driver,
and with OleDb Connection Strings use the keyword Provider.
About Oracle, The .Net framework have a namespace called System.Data.OracleClient, but it's deprecated (from Oracle and ADO.NET):
The types in System.Data.OracleClient are deprecated. The types remain supported in the current version of.NET Framework but will be removed in a future release. Microsoft recommends that you use a third-party Oracle provider.
I'm guessing Oracle's own ADO.Net implementation also works with it's own driver. If you really want to know, you can look it up in their documentation.
I've an oracle server, already installed on a remote server.
I've installed oracle latest provider, to use them in visual studio with entity framework.
But when I'm trying to connect to the server, I got this exception:
ORA-12560: TNS:protocol adapter error.
I'm really new to the oracle world, and I cannot find what is the problem or even how to debug it.
I saw that listeners are ups, by doing a lsnrctl status I've my listener on the port 1521.
But, I saw that i've the security like this: "Security ON: Local OS Authentication", but since I've no common users between the server and the client, can it make somes troubles?
Should I have some specials rights on my user? In local, I can connect myself with the sqldeveloper tools.
Any help would be greatly appreciated
EDIT
Some more informations:
The server runs under windows, it has the OracleXETNSListener service started. I forgot to mention, but the server firewall is off.
Edit 2
I tried to download the oracle sql developer on my workstation, and I connected myself with exactly the same informations.(I just saw that in fact sql developer use a "base" connection instead of "TNS", which seems to be used by the EF?
I ended by using the devart connector: http://www.devart.com/dotconnect/oracle/
it worked for me directly in all mode(Direct or normal). If only I did tried it this morning, I will have loosed less time.
Are you using your tns names via AD or locally on your machine? If it's local then you'll need to make sure that you have the correct connection descriptors listed in the tns names file located in the default location - this depends on Oracle version.
There are known issues around entity framework and connecting to remote instances, but these can be overcome with a l
Using the Oracle Provider, your connection string should look something like this:
Data Source={serverAddress}/xe;User Id={UserName};Password={Password};
Example:
Data Source=localhost/xe;User Id=scott;Password=tiger
I suggest you to always mention the Oracle Instance Identifier (which in the Express Edition is always xe), so you don't have to rely on your tns config settings.