// This example needs the 
// System.Data.SqlClient library
 
#region Building the connection string
 
string Server = "localhost";
string Username = "my_username";
string Password = "my_password";
string Database = "my_database";
 
string ConnectionString = "Data Source=" + Server + ";";
ConnectionString += "User ID=" + Username + ";";
ConnectionString += "Password=" + Password + ";";
ConnectionString += "Initial Catalog=" + Database;
 
#endregion
 
 
#region Try to establish a connection to the database
 
SqlConnection SQLConnection = new SqlConnection();
 
try
{
    SQLConnection.ConnectionString = ConnectionString;
    SQLConnection.Open();
 
    // You can get the server version 
    // SQLConnection.ServerVersion
}
catch (Exception Ex)
{
    // Try to close the connection
    if (SQLConnection != null)
        SQLConnection.Dispose();
 
    // Create a (useful) error message
    string ErrorMessage = "A error occurred while trying to connect to the server.";
    ErrorMessage += Environment.NewLine;
    ErrorMessage += Environment.NewLine;
    ErrorMessage += Ex.Message;
 
    // Show error message (this = the parent Form object)
    MessageBox.Show(this, ErrorMessage, "Connection error", MessageBoxButtons.OK, MessageBoxIcon.Error);
 
    // Stop here
    return;
}
 
#endregion
 
 
#region Execute a SQL query
 
string SQLStatement = "SELECT * FROM ExampleTable";
 
// Create a SqlDataAdapter to get the results as DataTable
SqlDataAdapter SQLDataAdapter = new SqlDataAdapter(SQLStatement, SQLConnection);
 
// Create a new DataTable
DataTable dtResult = new DataTable();
 
// Fill the DataTable with the result of the SQL statement
SQLDataAdapter.Fill(dtResult);
 
// Loop through all entries
foreach (DataRow drRow in dtResult.Rows)
{
    // Show a message box with the content of 
    // the "Name" column
    MessageBox.Show(drRow["Name"].ToString());
}
 
// We don't need the data adapter any more
SQLDataAdapter.Dispose();
 
#endregion
 
 
#region Close the database link
 
SQLConnection.Close();
SQLConnection.Dispose();
 
#endregion