Develop Reference

connect database with dataGridView

How can I connect my Trgovina.mdf with dataGridView?
I follow this tutorial, but it seems that program doesn't find my database.
Connection string looks like that:
string connString = #"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\Klemen\documents\visual studio 2012\Projects\Trgovina\Trgovina\Trgovina.mdf;Integrated Security=True";
Everything else is the same as tutorial example.
Error string is An OLE DB Provider was not specified in the ConnectionString. An example would be, 'Provider=SQLOLEDB;'
Full code looks like this.

The tutorial you talk about in your question use an Access Database and thus uses the OleDB engine to reach and work with the database. Instead your connection string use the syntax reserved for SQLServer LocalDB.
You should change your objects to SqlConnection (instead of OleDbConnection), SqlCommand (instead of OleDbCommand) and so on...
With these changes you should be able to connect to the automatic instance of SqlServer LocalDB. The rest of the tutorial could work or not, depending on what is present in the MDF file used.

You trying to connect to database .mdf file, but you have a wrong provider.
An MDF is a Microsoft SQL Server database not a Jet Database like
Access (*.mdb). You cannot just connect to the flat file and read it.
You would need to mount the database in an instance of SQL Server.
You could install SQL Server 2005 Express
Source
Note: Just download MS SQL Server 2005 Express or later and you must use the System.Data.SqlClient instead of OLE DB to solve your problem.

C# Database Connection Stored in DLL to Call

I am New to the more enhanced features of the C# and .NET coding practices
I have been trying to Find A solution to using a particular method in C# for Winforms, Windows Services And ASP.NET web Applications where you program your connection to SQL and Convert the C# Code file to a dll to be used in your project.
The idea is to Create the Connection and Convert it to a dll so that every time you start a function and need to make a database connection you will just write it where you say
Function ABC
{
//VB Version would be like this as i have seen this
Dim DCDLL as New Dataconn
//Where 'DCDLL' is the DLL file which is being declared as a new dataconnection
//C# Version would be Alon these Lines
SQLConnection DataConn = New SQLConnection(DCDLL)
}
I have only seen the VB Code version of the Call so I am not keen on the C# Method that this would be done
Meanwhile The DLL Holds all the other code like
string ConnectionString =
"Data Source=Datasource; UID=User; PWD=Pass; Persist Security
Info=True; Initial Catalog= Catalog";
Dataconn = new SqlConnection(ConnectionString);
Dataconn.Open();
the purpose of the DLL would be to handle the connection to the database, Open it catch errors if dataconnection is not successfull and close the connection if needed so that you dont have to programatically do this every time. Also it is only responsible for the connection therefore you can use a function to call the connection execute the procedure and whatever else is required.
The idea of using a DLL is just to make the Connection settings to the Database a little more secure, the Connection obviously wont become super secure but it adds more security than having the Code in you code pages etc.
i have spoken to and seen people use this type of method but my research on how to achieve this via google and other sources does not seem to understand what i am searching for.
I am trying to understand that when i code this file how it must be done as to ensure that it handles the database connection correctly without issues and doesnt break.
If anyone can Give me Examples in C# of how to do this it would be appreciated or if you know of any pages that have explained how to achieve this i would be most grateful for your assistance

You should put your connection strings in app.config / web.config, and use c# to get the values...
Get ConnectionString from app.config in c#
You can also encrypt the connection string...
http://msdn.microsoft.com/en-us/library/89211k9b(v=vs.80).aspx

Create connection to database in VS2010 without SQL Client - dynamically

How to create connection to database in VS2010 without SQL Client dynamically?
I tried using ConnectionStringSettings and SqlConnection and I succeeded, but I'm not supposed to use SQL Client.
I'm using Massive.

You should be able to use System.Data.OleDb.OleDbConnection.
Use a connection string like this:
Provider=SQLOLEDB;Server=myServerAddress;Database=myDataBase;Uid=myUsername; Pwd=myPassword;

It might be that you just miss to reference System.Configuration in your project and consequently Massive cannot find the connection string in your app.config.
Following the instructions on github I could query my SQL Express database without any problems using Massive having a plain SqlClient connection string in my app.config.

Is there a generic way of dealing with varying connection strings in C#?

I have an application that needs to connect to a SQL database, and execute a SQL Agent Job.
The connection string I am trying to access is stored in the registry, which is easily enough pulled out.
This appliction is to be run on multiple computers, and I cannot guarantee the format of this connection string being consistent across these computers. Two that I have pulled out for example are:
Data Source=Server1;Initial Catalog=DB1;Integrated Security=SSPI;
Data Source=Server2;Initial Catalog=DB1;Provider=SQLNCLI.1;Integrated Security=SSPI;Auto Translate=False;
I can use an object of type System.Data.SqlClient.SqlConnection to connect to the database with the first connection string, howevever, I get the following error when I pass the second to it:
keyword not supported: 'provider'
Similarly, I can use the an object of type System.Data.OleDb.OleDbConnection to connect to the database with the second connection string, howevever, I get the following error when I pass the first to it:
An OLEDB Provider was not specified in the ConnectionString'
I can solve this by scanning the string for 'Provider' and doing the connect conditionally, however I can't help but feel that there is a better way of doing this, and handle the connection strings in a more generic fashion.
Does anyone have any suggestions?

The normal way of handling this is storing the ADO.NET provider unique name (separately from the connection string) and using a DB Provider Factory.

Use a SqlConnectionStringBuilder, initialize it with the connection string you find in registry and then read its ConnectionString property, which would normalize the connection string to proper SQL Client syntax.

concurrent SqlConnection and EntityConnection to a local Sql Express Server

I'm using Linq2Entity for most of my database operations. However for database creation, table creation and initial data insertion I use plain SQL files. Therefore I need both an SqlConnection and an EntityConnection. Unfortunately the Entity Framework starts complaining that the Sql Server is not listening on the other end of the pipe.
I'm not sure what the problem is here, it could be due to user instancing. Clearing the pool of the SqlConnection or disposing the connection instance does not help.
The connection string I'm using is the following:
"Data Source=.\SQLEXPRESS; Initial Catalog=dbname; Integrated Security=SSPI;"
update:
I have tried to use the EntityConnection for database maintenance purposes but I'm running into troubles. I can't use the EntityConnection to create databases and drop databases. The following syntax is unsupported for an EntityConnection but works fine for an SqlConnection to ms SQL express.
CREATE DATABASE silverfit ON ( NAME = silverfit, FILENAME = 'c:\silverfit\silverfit.mdf' );
Also for some reason the EntityConnection does not allow me to change databases which is necessary to drop a database. I'm afraid I still need the SqlConnection to create the database and tables..
Is there a way for SqlConnections and EntityConnections to coexist for local ms SQL express databases?
Thanks,
Wouter

Have you tried creating a SqlConnection which you then pass to the constructor for your EntityConnection? One of the overloads for EntityConnection takes a MetadataWorkspace and a DbConnection (from which SqlConnection derives.) The slight drawback of this is that you must create your MetadataWorkspace manually, which gathers up the .csdl, .ssdl, and .msl files that define your workspace. However, in the long run, you should be able to share a single connection for both executing DML queries, and using Entity Framework.

I don't agree that you need a plain SQL connection and Entity connection for this task, at least as you've described it. You can execute SQL using the Entity connection. Look at EntityConnection.CreateDbCommand. Naturally, there's a danger here that you are doing DB-server-specific things on a non-DB-server-specific instance like a EntityConnection. But it probably beats having a separate connection, in this case.

Did you try to use the EntityConnection.StoreConnection to retrieve the SqlConnection and execute commands with it ?

If you're trying attaching your database file to SQL Server Express at run time, which it seems as if you are, then only one connection can be open on it at once. This is a problem for other things, not just what you're trying to accomplish. Say, for instance, you connect to 'c:\silverfit\silverfit.mdf' through the server explorer in VS and try to open one of the tables in the db. After you open the table, try running your application. It will bomb.
However, if you open up SQL Management Studio Express (you can download it here), and then attach the database to the SQL Server, the problems you are experiencing should go away. At that point you should be able to open multiple connections to your database, via SQLConnection or EntityConnection.
Attaching your database at run time to the SQL Server express engine really only works well for demoing purposes, or proof of concepts.

Is ADO.NET holding a connection open to the database through connection pooling? Try adding Pooling=False to the connection string, as this may allow the database to be closed before you drop it.