con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Extended Properties=dBASE IV;User ID=;Password=;Data Source="+System.IO.Directory.GetCurrentDirectory());
....
cmd.CommandText="insert into TableName (FieldChar, FieldNumeric) values (?, ?)";
CommandDest.Parameters.Add("FieldChar",OleDbType.VarChar); // 1 
CommandDest.Parameters.Add("FieldNumeric",OleDbType.Numeric); // 2 

CommandDest.Parameters["FieldChar"].Value="A";
CommandDest.Parameters["FieldNumeric"].Valie= 1 ;

CommandDest.Parameters["FieldNumeric"].Valie=row["FieldSrc"];
||
CommandDest.Parameters["FieldNumeric"].Valie=Convert.ToDecimal(row["FieldSrc"]);
||
CommandDest.Parameters["FieldNumeric"].Valie=Convert.ToDouble(row["FieldSrc"]);