Excel “External table is not in the expected format.” .

Question:

I'm trying to read an Excel (xlsx) file using the code shown below. I get an "External table is not in the expected format." error unless I have the file already open in Excel. In other words, I have to open the file in Excel first before I can read if from my C# program. The xlsx file is on a share on our network. How can I read the file without having to open it first? Thanks

string sql = "SELECT * FROM [Sheet1$]";  string excelConnection = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathname + ";Extended Properties=/"Excel 8.0;HDR=YES;IMEX=1;/"";    using (OleDbDataAdapter adaptor = new OleDbDataAdapter(sql, excelConnection)) {  DataSet ds = new DataSet();  adaptor.Fill(ds);  }  

Answers:

"External table is not in the expected format." typically occurs when trying to use an Excel 2007 file with a connection string that uses: Microsoft.Jet.OLEDB.4.0 and Extended Properties=Excel 8.0

Using the following connection string seems to fix most problems.

public static string path = @"C:/src/RedirectApplication/RedirectApplication/301s.xlsx";  public static string connStr = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=Excel 12.0;";
以上出處：

很多人換了2010後，問的最多的問題之一是2003裡最經典的ADO中的“provider=Microsoft.Jet.OLEDB.4.0”這句怎麼不能用了。

百度一下可以瞭解到，Microsoft.Jet.OLEDB.4.0是Microsoft Jet引擎，這適用於2003版本（2003之前的我沒裝，所以也不知道能向下適應到哪個版本），而在2007中，微軟對其旗下 Access 與 Excel 的主要檔案格式進行修改，並且重新命名為 .accdb（Access 2007 資料庫檔案）與 .xlsx（Excel 2007 檔案），因此未被 Microsoft Jet 引擎所支援，不過微軟也很快的提出了Microsoft Office 2007 Desktop Drivers: Data Connectivity Components 來支援，目前的解決方法就是把連線字串中的資料提供者改為Microsoft.ACE.OLEDB.12.0。

//2003（Microsoft.Jet.Oledb.4.0）
string strConn = string.Format("Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'", excelFilePath);

//2010（Microsoft.ACE.OLEDB.12.0）
string strConn = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'", excelFilePath);