[重奖100分]帮我看一下，读Excel问题

public static String[] GetExcelSheetNames(string excelFile)
    {
        OleDbConnection objConn = null;
        System.Data.DataTable dt = null;

        try
        {
            //string strConn = "Provider=Microsoft.Jet.OleDb.4.0;" + "data source=" + excelFile + ";Extended Properties='Excel 8.0; HDR=NO; IMEX=1'"; //此连接只能操作Excel2007之前(.xls)文件

            string strConn = "Provider=Microsoft.Ace.OleDb.12.0;" + "data source=" + excelFile + ";Extended Properties='Excel 12.0; HDR=NO; IMEX=1'"; //此连接可以操作.xls与.xlsx文件
            objConn = new OleDbConnection(strConn);
            objConn.Open();
            dt = objConn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
            if (dt == null)
            {
                return null;
            }
            String[] excelSheets = new String[dt.Rows.Count];
            int i = 0;
            foreach (DataRow row in dt.Rows)
            {
                excelSheets[i] = row["TABLE_NAME"].ToString();
                i++;
            }

            return excelSheets;
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            return null;
        }
        finally
        {
            if (objConn != null)
            {
                objConn.Close();
                objConn.Dispose();
            }
            if (dt != null)
            {
                dt.Dispose();
            }
        }
    }

    public static DataTable GetExcelToDataTableBySheet(string FileFullPath, string SheetName)
    {
        //string strConn = "Provider=Microsoft.Jet.OleDb.4.0;" + "data source=" + FileFullPath + ";Extended Properties='Excel 8.0; HDR=NO; IMEX=1'"; //此连接只能操作Excel2007之前(.xls)文件
        try
        {
            string strConn = "Provider=Microsoft.Ace.OleDb.12.0;" + "data source=" + FileFullPath + ";Extended Properties='Excel 12.0; HDR=NO; IMEX=1'"; //此连接可以操作.xls与.xlsx文件
            OleDbConnection conn = new OleDbConnection(strConn);
            conn.Open();
            DataSet ds = new DataSet();
            OleDbDataAdapter odda = new OleDbDataAdapter(string.Format("SELECT * FROM [{0}]", SheetName), conn);                    //("select * from [Sheet1$]", conn);
            odda.Fill(ds, SheetName);
            conn.Close();
            return ds.Tables[0];
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            return null;
        }

    }

调用
string[] abc = GetExcelSheetNames(Server.MapPath("/accessories/xls/" + pname));
        loadExcelSheet(GetExcelToDataTableBySheet(Server.MapPath("/accessories/xls/a" + pname), abc[0]));

为什么会出现下述错误？？？？？

[NullReferenceException: 未将对象引用设置到对象的实例。]
   system_dingcang_loadExcel.Button1_Click(Object sender, EventArgs e) +630
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +111
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565

各位大侠，谁能给我解答一下，重奖100分，谢谢啦

下跪 --------------------编程问答-------------------- 1，Server.MapPath("/accessories/xls/" + pname)打印出来看什么，存在吗？还有Server.MapPath("/accessories/xls/a" + pname)存在吗？

2，abc.Length>0才能继续执行 abc[0] --------------------编程问答-------------------- --------------------编程问答-------------------- 只是一段，NullReferenceException: 未将对象引用设置到对象的实例，这一般是没有初始实例化

补充：.NET技术 ,  C#