Excel外部表格不是预期的格式

我从同一个Excel文件运行这个代码两次，它工作正常，我得到正确的表。 但是，当我尝试运行它第三次崩溃，并引发外部表格不是预期的格式。

Filename = filename; if (ExcelSet == null) { string HDR = firstRowContainsColumnNames ? "Yes" : "No"; string strConn; if (filename.Substring(filename.LastIndexOf('.')).ToLower() == ".xlsx") { strConn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + Filename + ";Extended Properties=\"Excel 12.0;HDR=" + HDR + ";IMEX=1\""; } else if (filename.Substring(filename.LastIndexOf('.')).ToLower() == ".xls") { strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Filename + ";Extended Properties=\"Excel 8.0;HDR=" + HDR + ";IMEX=1\""; } else { throw new Exception("File is not an Excel file"); } DataSet ds = new DataSet(); using (OleDbConnection conn = new OleDbConnection(strConn)) { if (conn.State != ConnectionState.Open) { conn.Open(); } DataTable schemaTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" }); foreach (DataRow schemaRow in schemaTable.Rows) { string sheet = schemaRow["TABLE_NAME"].ToString(); if (!sheet.EndsWith("_")) { try { OleDbCommand cmd = new OleDbCommand("SELECT * FROM [" + sheet + "]", conn); cmd.CommandType = CommandType.Text; DataTable outputTable = new DataTable(sheet); ds.Tables.Add(outputTable); new OleDbDataAdapter(cmd).Fill(outputTable); outputTable.Dispose(); } catch (Exception ex) { throw new Exception(ex.Message + string.Format("Sheet: {0}.File.F{1}", sheet, Filename), ex); } } } conn.Close(); conn.Dispose(); } ExcelSet = ds; } 

我不知道为什么它会出现问题，任何人都有同样的问题？