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;";