Access to report file denied. Another program may be using it.(水晶报表导出PDF时的异常)

ReportDoc.Load(Server.MapPath("../Report") + "\\CrystalReport2.rpt");            SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=Buyautomation;User ID=sa;Password=123456");            SqlCommand comm = new SqlCommand("SELECT * FROM View_tbOperate", conn);            SqlDataAdapter adapter = new SqlDataAdapter();            if (conn.State == ConnectionState.Closed) conn.Open();            // get data from db            DataSet2 ds = new DataSet2();            adapter.SelectCommand = comm;            adapter.Fill(ds, "View_tbOperate");            conn.Close();            // set data to report            ReportDoc.SetDataSource(ds);            ReportDoc.Refresh();            // set output type "pdf"            ReportDoc.ExportOptions.ExportDestinationType = ExportDestinationType.DiskFile;            ReportDoc.ExportOptions.ExportFormatType = ExportFormatType.PortableDocFormat;            CrystalDecisions.Shared.DiskFileDestinationOptions options = new CrystalDecisions.Shared.DiskFileDestinationOptions();            options.DiskFileName = Server.MapPath("../DOC") + "\\Chap0101.pdf";            ReportDoc.ExportOptions.DestinationOptions = options;            FileLockedThenWait(Server.MapPath("../DOC") + "\\Chap0101.pdf");            if (File.Exists(Server.MapPath("../DOC") + "\\Chap0101.pdf"))            {                File.Delete(Server.MapPath("../DOC") + "\\Chap0101.pdf");            }            ReportDoc.Export();            //set data to view            //this.CrystalReportViewer1.ReportSource = ReportDoc;