OleDbConnection con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; data source=data.mdb");
con.Open();
OleDbCommand dc=new OleDbCommand("select name from us where id=2", con);
textBox1.Text=dc.ExecuteScalar().ToString();

OleDbConnection con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; data source=data.mdb");
con.Open();
OleDbCommand dc=new OleDbCommand("insert into us (name) values (11)", con);
dc.ExecuteNonQuery();
con.Close();

string us=textBox2.Text;
string pa=textBox1.Text;
OleDbConnection con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; data source=data.mdb"); 
OleDbCommand oldC=new OleDbCommand("insert into users (username, userpassword) values (@username, @userpassword)", con);
oldC.Parameters.Add("@username", us);
oldC.Parameters.Add("@userpassword", pa);
con.Open();
oldC.ExecuteNonQuery();
con.Close();
MessageBox.Show("Register successful!");
this.Dispose();