Ваше поле данных RTF должно быть "Memo".
private void InsertToMemo()
{
using (OleDbConnection oleDbConn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\AD.mdb"))
{
OleDbCommand oleDbCmd = new OleDbCommand("insert into Table2 values(1,'" + this.richTextBox1.Rtf + "')", oleDbConn);
oleDbCmd.Connection.Open();
oleDbCmd.ExecuteNonQuery();
}
}
private void ReadFormMemo()
{
using (OleDbConnection oleDbConn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\AD.mdb"))
{
OleDbCommand oleDbCmd = new OleDbCommand("select Field1 from Table2", oleDbConn);
oleDbCmd.Connection.Open();
OleDbDataReader oleDbDataReader = oleDbCmd.ExecuteReader();
oleDbDataReader.Read();
this.richTextBox2.Rtf = oleDbDataReader.GetString(0);
}
}