一个可能比较简单的关于读取excel的问题

我把excel当成一个数据库来查询，但是遇到一个问题，当一个字段（第一个字段mpg）里有小数（一位小数）而且还有整数的时候，读出的结果里有整数的那个记录的那个字段是空值，不知道为什么，代码我看上去是很标准的读取数据的代码，百思不得其解，望大虾们请教。 
public DataSet GetDataSetFromExcel(string FileName , string strSQL ) 
        {
            try
            {   
                //Skapa connectionstring till excel-filen
                StringBuilder connectionStringBuilder = new StringBuilder();
                connectionStringBuilder.Append("Provider=Microsoft.Jet.OLEDB.4.0;");
                connectionStringBuilder.Append("Data Source=");
                connectionStringBuilder.Append(FileName);
                connectionStringBuilder.Append(";Extended Properties=");
                connectionStringBuilder.Append(Convert.ToChar(34));
                connectionStringBuilder.Append("Excel 8.0;HDR=Yes;IMEX=2");
                connectionStringBuilder.Append(Convert.ToChar(34));                String connectionString = connectionStringBuilder.ToString();                //Anslut till filen
                OleDbConnection connection =new OleDbConnection(connectionString);
                
                connection.Open();                //Skapa SQL-kommando
                OleDbCommand command = new OleDbCommand(strSQL, connection);//"SELECT * FROM [" + WorksheetName + "$]", connection);                //Skapa data-adapter
                OleDbDataAdapter dataAdapter = new OleDbDataAdapter();
                dataAdapter.SelectCommand = command;                DataSet dataSet = new DataSet();
                dataAdapter.Fill(dataSet);                connection.Close();                dataAdapter.Dispose();
                command.Dispose();
                connection.Dispose();                //Returnera dataset:et
                return dataSet;
            }
            catch(Exception e)
            {
                System.Windows.MessageBox.Show(e.ToString(), "error");
                return null;
            }
        }mpg cylinders horsepower accel year weight origin make model price
43.1 4 48 21.5 78 1985 GERMANY Volkswagen Rabbit Dl  2400
36.1 4 66 14.4 78 1800 USA Ford       Fiesta     1900
32.8 4 52 19.4 78 1985 JAPAN Mazda      GLC Deluxe 2200
39.4 4 70 18.6 78 2070 JAPAN Datsun     B210 GX    2725
36.1 4 60 16.4 78 1800 JAPAN Honda      Civic CVCC 2250
19.9 8 110 15.5 78 3365 USA Oldsmobile Cutlass    3300
19.4 8 140 13.2 78 3735 USA Dodge      Diplomat   3125
20.2 8 139 12.8 78 3570 USA Mercury    Monarch    2850
19.2 6 105 19.2 78 3535 USA Pontiac    Phoenix    2800
20.5 6 95 18.2 78 3155 USA Chevrolet  Malibu     3275
20.2 6 85 15.8 78 2965 USA Ford       Fairmont A 2375
25.1 4 88 15.4 78 2720 USA Ford       Fairmont M 2275
20.5 6 100 17.2 78 3430 USA Plymouth   Volare     2700
19.4 6 90 17.2 78 3210 USA AMC        Concord    2300
20.6 6 105 15.8 78 3380 USA Buick      Century    3300
20.8 6 85 16.7 78 3070 USA Mercury    Zephyr     2425
18.6 6 110 18.7 78 3620 USA Dodge      Aspen      2700
18.1 6 120 15.1 78 3410 USA AMC        Concord D1 2425
19.2 8 145 13.2 78 3425 USA Chevrolet  MonteCarlo 3900
17.7 6 165 13.4 78 3445 USA Buick      RegalTurbo 4400
18.1 8 139 11.2 78 3205 USA Ford       Futura     2525
17.5 8 140 13.7 78 4080 USA Dodge      Magnum XE  3000
30 4 68 16.5 78 2155 USA Chevrolet  Chevette   2100