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Changing connection string dynamically on runtime in WinForms

I am making Winform dekstop application. I am giving an option in my application that user can select database or set database path. when user select database or database path then connection string should be changed at runtime in APP.config.

You probably shouldn't try and change the connection string in the config at runtime. You could have a set of possible connection strings in the <connectionStrings> section of the config file, allow the user to choose what database they want to use and read the appropriate connection from the file.

Even if there is no special needing for connection strings being stored in the standard way in the configuration file,it could be convenient to have a bounch of named <connectionStrings> in the standard configuration file and you can enumerate it like this:
foreach (ConnectionStringSettings c in System.Configuration.ConfigurationManager.ConnectionStrings)
{
//present the name in some combo etc etc.
}
then the user can select the connection string based on a friendly name.
The configuration file for your app will look like:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
.....
<connectionStrings>
<add name="connection1" connectionString="Data Source=your connection string 1" />
<add name="connection2" connectionString="Data Source=your connection string 2" />
<add name="connection3" connectionString="Data Source=your connection string 3" />
</connectionStrings>
....

Is the path of database file effects connection string??? One database is in my "C:\ProgramFiles\SQLEXPRESS\data\abc.mdf" and same database with same name is in "F:\mydb\abc.mdf" both database have same connection string or not????

How to set connectionstring at web.config file programmatically or dynamically?

I'm trying to create an ASP.NET website. There I'm using a database. To connect with the database I'm using the connectionstring which I've stored in the web.config file like
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=G:\CarRentalServices\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>
</connectionStrings>
and at code behind
private string _connectionString = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
So you can see the database is stored at G:\path\to\db\CarRentalServiceDB.mdf.
But now if my friend want to take the project from me and try to run the project from his machine then he has to change the connectionString at web.config. Say the website is now at D:\path\to\db\foo\CarRentalServiceDB.mdf in my friend's machine, then the connectionString needs to change. Isn't it tedious?
Is there any way to change the connectionString dynamically with any batch file or code so that it will change with respect to the current directory it is residing now?

You shoud use the |DataDirectory| token: http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring.aspx
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>

You would add multiple connections strings in your web.config file and call the one you need like
Web.config File
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=G:\CarRentalServices\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>
<add name="DBConnectionStringTwo"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=D:\path\to\db\foo\CarRentalServiceDB.mdf;Integrated Security=True"/>
</connectionStrings>
Code for connection strings
//Connection String 1
private string _connectionString = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
//Connection String 2
private string _connectionString2 = ConfigurationManager.ConnectionStrings["DBConnectionStringTwo"].ConnectionString;

How to connect database by using username and password in .net c#

I'm new to .net c#, hope this question is not sound silly. How can I connect to the database in web.config by using the username and password??
Example:
Following is the connection strings that I used to connect to the database. How could I write/set so that I can set the username (username = test) and password (password = abc123) for this connection strings and so that it will allows me to access to the database?
<connectionStrings>
<add name="aConnectionString" connectionString="Data Source=AAA-LLLL-SQL-00;Initial Catalog=Database_Name;Connect Timeout=1;Integrated Security=True;" providerName="System.Data.SqlClient"/>
</connectionStrings>

Try something like this.
<connectionStrings>
<add name="aConnectionString" connectionString="Data
Source=AAA-LLLL-SQL-00;Initial Catalog=Database_Name;User Id=myUsername;Password=myPassword"
providerName="System.Data.SqlClient"/>
</connectionStrings>

Use this to pull your connection string from the web.config.
http://msdn.microsoft.com/en-us/library/ms178411.aspx
Then you will use the .net Sql Provider to create a connection.
using(SqlConnection con = new SqlConnection(connectionstring))
{
con.Open();
// Perform operations here
}

Are you trying from IIS?
Then you need to grant your App Pools account access to SQL Server.
CREATE LOGIN [IIS APPPOOL\ASP.NET v4.0] FROM WINDOWS WITH DEFAULT_DATABASE=[AAA-LLLL-SQL-00], DEFAULT_LANGUAGE=[us_english]
GO

Reference for ADO and ADO.NET connection strings http://www.sqlstrings.com/

<connectionStrings>
<add name="aConnectionString" connectionString="Server={ip};Database= {databasename}; User Id={username}; Password={password}"/>
</connectionStrings>
This should work replace {...} with your values.

<connectionStrings>
<add name="aConnectionString" connectionString="Data Source=AAA-LLLL-SQL-00;Initial Catalog=Database_Name; User Id=your username; Password=pwd;" providerName="System.Data.SqlClient"/>
</connectionStrings>

C# Sql Connection String Across Pages

If I have several pages what would be the correct procedure in creating a connection string variable and sharing it among all of my pages. I would prefer not to type the connection string 100 times for each page and would just rather call it. Can I create it in my namespace or whats the best approach?

Put the connection string in the web.config file. See the following on MSDN: How to: Read Connection Strings from the Web.config File
Example of connection string in config:
<connectionStrings>
<add name="Movies2"
connectionString="Data Source=(local);Initial Catalog=Movies;User ID=wt3movies;Password=lalalalala;Integrated Security=SSPI"
providerName="System.Data.SqlClient" />
</connectionStrings>
Using the string:
string connStr = ConfigurationManager.ConnectionStrings["Movies2"].ConnectionString;

It's typically in your configuration file (web.config)

can't you use the <connectionStrings/> configuration ?
http://msdn.microsoft.com/en-us/library/ms178411.aspx

Well i would have included Setting file and placed it over there.It may be not the best bet but works for me.

There are many options. It depends on what data access methodology you are using. I would suggest creating a class to handle loading the connection string from the web.config file and exposing it as a public property.

There are a variety of ways to approach this which would delve in to architecture/SOC/IoC/Repository/ etc, but to answer your question in its simplest possible sense, you could create a Database class that had a single method that fetched your connection string from configuration.
internal class DataAccess
{
static string GetDatabaseConnection()
{
return ConfigurationManager.ConnectionStrings["AppDb"].ConnectionString;
// where AppDb is defined in your web.config/app.config.
}
}
Your pages could just use:
string connection = DataAccess.GetDatabaseConnection();

connection strings are usually stored in configuration files such as the web config. Here is a simple example
add something like this to the config
<connectionStrings>
<add
name="NorthwindConnectionString"
connectionString="Data Source=serverName;Initial
Catalog=Northwind;Persist Security Info=True;User
ID=userName;Password=password"
providerName="System.Data.SqlClient"
/>
</connectionStrings>
and then retrive it as
System.Configuration.Configuration rootWebConfig =
S
ystem.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/MyWebSiteRoot");
System.Configuration.ConnectionStringSettings connString;
if (rootWebConfig.ConnectionStrings.ConnectionStrings.Count > 0)
{
connString =
rootWebConfig.ConnectionStrings.ConnectionStrings["NorthwindConnectionString"];
if (connString != null)
Console.WriteLine("Northwind connection string = \"{0}\"",
connString.ConnectionString);
else
Console.WriteLine("No Northwind connection string");
}
full article is here http://msdn.microsoft.com/en-us/library/ms178411.aspx

You should keep it in you config file. For winforms that will be app.config, and for webforms it's web.config. Here is the section you need to have (for winforms).
<connectionStrings>
<add name="MyNameSpace.Properties.Settings.ConnectionString1"
connectionString="Data Source=MYSQLSERVER;Initial Catalog=DATABASENAME;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
Then you can access the connection string like this (depending on your .NET version - this is for 2.0)
string connectionString = ((string)(configurationAppSettings.GetValue(ConnectionString1"", typeof(string))));

Have the connection string (CS) in (App/Web).Config file and have the CS returned from a static method GetConncectionString().It means, this particular static method would be used in all the pages where CS is required.

You can also make a file called connectionStrings.config,or a name you choose, with this content:
<connectionStrings>
<add name="MyConnection" connectionString="server=MyServer; database=MyDataBase; user id=myUser; pwd=MyPwd;"/>
</connectionStrings>
And then, in your Web.Config
Insert this tag under node
<connectionStrings configSource="connectionStrings.config"/>

Multiple SQL Server connection strings in app.config file

I'm interested in displaying in a Windows Forms app a list of N radio buttons for the user to choose a target database server. I would like to add the SQL Server connection strings in the app.config file, so they are read by the app at runtime and rendered in the windows form as radio buttons.
At first I thought of using a delimiter to separate the connections
<appSettings>
<add key="ConnectionString" value="connection1|user id=user;password=123;server=10.0.0.1;database=myDatabase;connection timeout=30|connection2|user id=user;password=123;server=10.0.0.2;database=myDatabase;connection timeout=30"/>
</appSettings>
And then split the key value pairs.
Is it possible to do this in a different way?

To find all defined connection strings from your app.config, use the ConfigurationManager (from System.Configuration).
It has an enumeration: ConfigurationManager.ConnectionStrings which contains all entries in your <connectionStrings>.
You can loop over it with this code:
foreach(ConnectionStringSettings css in ConfigurationManager.ConnectionStrings)
{
string name = css.Name;
string connString = css.ConnectionString;
string provider = css.ProviderName;
}
The Name is just the symbolic name you give your connection string - it can be anything, really.
The ConnectionString is the connection string itself.
The ProviderName is the name of the provider for the connection, e.g. System.Data.SqlClient for SQL Server (and others for other database system). If you omit the providerName= attribute from your connection string in config, it defaults to SQL Server (System.Data.SqlClient).
Marc

Use the connectionStrings section to define your connection strings.
<connectionStrings>
<add name="connection1" connectionString="user id=user;password=123;server=10.0.0.1;database=myDatabase;connection timeout=30"/>
<add name="connection2" connectionString="user id=user;password=123;server=10.0.0.2;database=myDatabase;connection timeout=30"/>
</connectionStrings>

Yes, it is possible to do this in another way. Check the connectionStrings section that you can make in the app.config file.
<configuration>
<connectionStrings>
<add name="" connectionString=""/>
<add name="" connectionString=""/>
</connectionStrings>
</configuration>

We can declare multiple connection string under Web.Config or App.Config
<connectionStrings>
<add name="SourceDB" connectionString="..." />
<add name="DestinationDB" connectionString="..." />
</connectionStrings>
In DAL or .cs file you can access connection strings like this string SounceConnection = ConfigurationManager.ConnectionStrings["SourceDB"].ConnectionString;
string DestinationConnection = ConfigurationManager.ConnectionStrings["DestinationDB"].ConnectionString;

You can use the AppSettings class, get a list of all keys that start with ConnectionString and display them.
Your config file will look like this:
<appSettings>
<add key="ConnectionString_Name1" value="..."/>
<add key="ConnectionString_Name2" value="..."/>
<add key="ConnectionString_Name3" value="..."/>
</appSettings>
You can get the name, by splitting the key name (using "_" in this example).
BTW: You should also use the ConnectionStrings section, you are only interrested in connection strings.

This is how to use LINQ to get list of connection strings:
List<string> connectionStrings = ConfigurationManager.ConnectionStrings
.Cast<ConnectionStringSettings>()
.Select(v => v.ConnectionString)
.ToList();
Or you can build a dictionary of it:
Dictionary<string/*name*/, string/*connectionString*/> keyValue = ConfigurationManager.ConnectionStrings
.Cast<ConnectionStringSettings>()
.ToDictionary(v => v.Name, v => v.ConnectionString);