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;";
以上出处：http://blog.csdn.net/ldl22847/article/details/6322339

很多人换了2010后，问的最多的问题之一是2003里最经典的ADO中的“provider=Microsoft.Jet.OLEDB.4.0”这句怎么不能用了。

百度一下可以了解到，Microsoft.Jet.OLEDB.4.0是Microsoft Jet引擎，这适用于2003版本（2003之前的我没装，所以也不知道能向下适应到哪个版本），而在2007中，微软对其旗下 Access 与 Excel 的主要文件格式进行修改，并且重命名为 .accdb（Access 2007 数据库文件）与 .xlsx（Excel 2007 文件），因此未被 Microsoft Jet 引擎所支持，不过微软也很快的提出了Microsoft Office 2007 Desktop Drivers: Data Connectivity Components 来支持，目前的解决方法就是把连接字符串中的数据提供者改为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);