Change Sql Connection String Dynamically

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We can easily to read Sql Connection String from config file such as app.config and web.config. But how can we change string items in run time ?

We can use DbConnectionStringBuilder class to implement it:

Firstly, we can get Connection String:

String connStr = ConfigurationManager.ConnectionStrings[�WinTerminalDBConnString�].ConnectionString;

then, transfer the connection string to DBConnectionStringBuilder;

dbConnBuilder.ConnectionString = connStr;

then you can follow the following code to use dbConnBuilder.Add or _dbConnBuilder.Remove methods to change Connection string:

The following code copied from Microsoft MSDN:

static void Main()
{
    DbConnectionStringBuilder builder =
        new DbConnectionStringBuilder();
    builder.ConnectionString = @�Data Source=c:\MyData\MyDb.mdb�;
    builder.Add(�Provider�, �Microsoft.Jet.Oledb.4.0�);
    builder.Add(�Jet OLEDB:Database Password�, �*******�);
    builder.Add(�Jet OLEDB:System Database�,
        @�c:\MyData\Workgroup.mdb�);
    // Set up row-level locking.
    builder.Add(�Jet OLEDB:Database Locking Mode�, 1);
// The DbConnectionStringBuilder class 
    // is database agnostic, so it�s possible to 
    // build any type of connection string using 
    // this class.

    // The ConnectionString property may have been 
    // formatted by the DbConnectionStringBuilder class.
    OleDbConnection oledbConnect = new
        OleDbConnection(builder.ConnectionString);
    Console.WriteLine(oledbConnect.ConnectionString);

    // Use the same DbConnectionStringBuilder to create 
    // a SqlConnection object.
    builder.Clear();
    builder.Add(�integrated security�, true);
    builder.Add(�Initial Catalog�, �AdventureWorks�);
    builder.Add(�Data Source�, �(local)�);

    SqlConnection sqlConnect = new
        SqlConnection(builder.ConnectionString);
    Console.WriteLine(sqlConnect.ConnectionString);

    // Pass the DbConnectionStringBuilder an existing 
    // connection string, and you can retrieve and
    // modify any of the elements.
    builder.ConnectionString = �server=(local);user id=*******;� +
        �password=*******;initial catalog=AdventureWorks�;
    builder[�Server�] = �.�;
    builder.Remove(�User ID�);

    // Note that calling Remove on a nonexistent item doesn�t
    // throw an exception.
    builder.Remove(�BadItem�);

    // Setting the indexer adds the value if 
    // necessary.
    builder[�Integrated Security�] = true;
    builder.Remove(�password�);
    builder[�User ID�] = �Hello�;
    Console.WriteLine(builder.ConnectionString);

    Console.WriteLine(�Press Enter to finish.�);
    Console.ReadLine();
}

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