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Store connection string in database and retrieve it on application startup

I am developing an winforms application in VS 2010 to retrive data from Sql Server or MySql to Sql Server or MySql.
My design is something like this.
So here I am storing all values of connection string in Sql Server database table in separate column.
I am able to get the required fields and validate them, test them and store it in database but I am stuck at how to get the stored connection string at runtime to work and how to use the last selected connection string?
guidance please.

Your config file might have a connectionStrings section like this:
<connectionStrings>
<add name="ConnectionNumberOne"
connectionString="Data Source=ds;Initial Catalog=DB;Integrated Security=True"
providerName="System.Data.SqlClient" />
<add name="ConnectionNumberTwo"
connectionString="Data Source=ds2;Initial Catalog=DB2;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
You can read the connection string thusly:
var connectionOne = System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionNumberOne"];
var connectionTwo = System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionNumberTwo"];
And you can save the connection string as well:
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.ConnectionStrings.ConnectionStrings["ConnectionNumberOne"].ConnectionString = //CONCATINATE YOUR FIELDS TOGETHER HERE
config.Save(ConfigurationSaveMode.Modified, true);
ConfigurationManager.RefreshSection("connectionStrings");

Reading a connection string from a class library

I am currently struggling to read a connection string from the App.config inside my WinForms application from my Class Library (and Unit Testing).
I added a 'test' entry to the App.config;
<connectionStrings>
<add name="MyConnString" connectionString="Test;" />
</connectionStrings>
My TestMethod looks like this;
[TestMethod]
public void TestConnection1()
{
string connString = "";
if (ConfigurationManager.ConnectionStrings["MyConnString"] != null)
{
connString = ConfigurationManager.ConnectionStrings["MyConnString"].ConnectionString;
}
string expected = "Test;";
string actual = connString;
Assert.AreEqual(expected, actual);
}
This, obviously, fails. Actual's value is empty.
What am I doing wrong?

you need to add connection string key into Test project's config as well.

Regarding your comment to DJ Kraze: "#DJ KRAZE, If I put 0 as index, it returns me a connectionstring for SQLExpress "aspnetdb.mdf". If I put 1 as index, I get an exception (IndexOutOfRangeException), so obviously my string is not found."
The problem is you forgot the configuration element. For example:
Referenced from MSDN: Storing and Retrieving Connection Strings
<?xml version='1.0' encoding='utf-8'?>
<configuration>
<connectionStrings>
<clear />
<add name="Name"
providerName="System.Data.ProviderName"
connectionString="Valid Connection String;" />
</connectionStrings>
</configuration>
The machine.config file also contains a <connectionStrings> section, which contains connection strings used by Visual Studio. When retrieving connection strings by provider name from the app.config file in a Windows application, the connection strings in machine.config get loaded first, and then the entries from app.config. Adding clear immediately after the connectionStrings element removes all inherited references from the data structure in memory, so that only the connection strings defined in the local app.config file are considered.

How do I write an external connection string config file and make my c# application recognize and read it?

My current c# windows form application is using the following code to connect to a database to retrieve information and the it is stored at Setting.cs
public static String connectionString ="Data Source=####; Initial Catalog=###; User ID=####; Password='####'";
I have written out an external Connection.config file and the content would be :
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="Connection" providerName="System.Data.providername"
connectionString="Data Source=####; Initial Catalog=###; User ID=###; Password='####!';" />
</connectionStrings>
</configuration>
is the above code written correctly? as I sort of just copied and paste online and editted the connection string part as i do not know what does the "add name" and providerName part does.
what i would like to ask is where should i write the code in my forms to read the connection string from my external config file so i can remove the one in my setting.cs file.
thank you.
don mind the ### as it is just replaced by me to represent the information.

You can use config source to split your config files. Example App/web.config:
<connectionStrings configSource="myExternalConfigSource.xml" />
External Config:
<connectionStrings>
<add name="Connection" providerName="System.Data.providername"
connectionString="Data Source=####; Initial Catalog=###; User ID=###; />
</connectionStrings>
More info: http://www.nikhilk.net/Entry.aspx?id=158
If you use this method, you can reference your config as normal and still have your configuration split out into seperate files.

Add the following in your web.config file right at the bottom above the closing config tag.
<connectionStrings>
<add connectionString="Data Source=Servernamegoeshere;Initial Catalog=databasenamehere;Persist Security Info=True;User ID=***;Password=***" name="nameyouwanttogivethisconnection" providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>
To reference the connection on the page load of the main form use this:
public void Page_Load(object sender, EventArgs e)
{
string connectionString = ConfigurationManager.ConnectionStrings["nameyouwanttogivethisconnection"].ConnectionString;
SqlConnection SqlConnection = new SqlConnection(connectionString);
SqlCommand SqlCommand = new SqlCommand("update table etc etc....",SqlConnection);
SqlConnection.Open();
SqlCommand.ExecuteNonQuery(); //This line is for updates and inserts, use SqlCommand.ExecuteReader(CommandBehavior.CloseConnection); for select statments
SqlConnection.Close();
}
Make sure you add these references to the top of the page you are using this code on:
using System.Data;
using System.Configuration;
using System.Data.SqlClient;
You may then use that connection to create a Sqlcommand to run against your database.

we use:
<configuration>
<appSettings>
<add key="connection.string" value="Initial Catalog=XXX;server=localhost;User=YYY;Password=ZZZ;" />
</appSettings>
</configuration>
and then just:
ConfigurationManager.AppSettings["connection.string"];

You could also use ApplicationSettings, and forget about writing information in config files manually (It will be done automatically)
Right click on your project in solution explorer and select Properties.
Go to Settings tab.
Click on the link to create the settings file. (It will be called Settings.settings)
For Name, type the name you want to use for the connection string. (i.e. ConnectionString)
For Type, select Connection String
For Scope, select Application
For Value paste your connection string.
When you want to use it, just type
Application.Settings.Default.ConnectionString
i.e
SqlConnection connection = new SqlConnection(Application.Settings.Default.ConnectionString);

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);