string sqlText = @"SELECT * FROM [User] WHERE UserName= @name";

string sqlText = @"SELECT * FROM [User] WHERE UserName= ？";

OleDbCommand dataAction = new OleDbCommand(sqlText,linkDB);

dataAction.Parameters.AddWithValue("@name","wangyong");

using (OleDbConnection linkDB = new OleDbConnection(@" Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|/AiMeiLi.accdb"))
            {
                linkDB.Open();
                string sqlText = @"SELECT * FROM [User] WHERE UserName= @name";
                OleDbCommand dataAction = new OleDbCommand(sqlText,linkDB);
                dataAction.Parameters.AddWithValue("@name","wangyong");
                try
                {
                    OleDbDataReader scanItems = dataAction.ExecuteReader();
                    if (scanItems.HasRows)
                    {
                        while (scanItems.Read())
                        {
                            MessageBox.Show(scanItems[1].ToString());
                        }
                    }

                }
                catch (Exception ex)
                {
                    MessageBox.Show("Failure" + ex.Message);
                }
            }