how to get all databases in a server instance using c#

Try
http://msdn.microsoft.com/en-us/library/a6t1z9x2.aspx[^]
http://www.c-sharpcorner.com/UploadFile/iersoy/get-all-instances-of-sql-server-in-C-Sharp/[^]
http://www.ehsanenaloo.com/index.php/200/programming/csharp/how-to-find-all-sql-server-instance-running-in-local-network-c.html[^]
http://www.emrekurubas.com/blog/?p=147[^]

hii,
following commands will give database list
All the following Stored Procedure list all the Databases on Server.

I personally use EXEC sp_databases because it gives the same results as other but it is self explaining.
----SQL SERVER 2005 System Procedures
EXEC sp_databases
EXEC sp_helpdb
----SQL 2000 Method still works in SQL Server 2005
SELECT name
FROM sys.databases
SELECT name
FROM sys.sysdatabases
----SQL SERVER Un-Documented Procedure
EXEC sp_msForEachDB 'PRINT ''?'''

just call any one with ado.net and get data like below code

System.Data.SqlClient.SqlConnection SqlCon = new System.Data.SqlClient.SqlConnection("server=192.168.0.1;uid=sa;pwd=1234");
SqlCon.Open();

System.Data.SqlClient.SqlCommand SqlCom = new System.Data.SqlClient.SqlCommand();
SqlCom.Connection = SqlCon;
SqlCom.CommandType = CommandType.StoredProcedure;
SqlCom.CommandText = "sp_databases";

System.Data.SqlClient.SqlDataReader SqlDR;
SqlDR = SqlCom.ExecuteReader();

while(SqlDR.Read())
{
MessageBox.Show(SqlDR.GetString(0));
}

public List<string> GetDatabaseList()
{
    List<string> list = new List<string>();

    // Open connection to the database
    string conString = "server=xeon;uid=sa;pwd=manager; database=northwind";

    using (SqlConnection con = new SqlConnection(conString))
    {
        con.Open();

        // Set up a command with the given query and associate
        // this with the current connection.
        using (SqlCommand cmd = new SqlCommand("SELECT name from sys.databases", con))
        {
            using (IDataReader dr = cmd.ExecuteReader())
            {
                while (dr.Read())
                {
                    list.Add(dr[0].ToString());
                }
            }
        }
    }
    return list;

}
</string></string></string>