OleDbCommand
具体用法：

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();

C# 连接数据库