Thanks for this code :) I really appreciate it. Works for me.

public static string connStr = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=Excel 12.0;";

So if you have diff version of Excel file, get the file name, if its extension is .xlsx, use this:

Private Const connstring As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=Excel 12.0;";

and if it is .xls, use:

Private Const connstring As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=" + path + ";Extended Properties=""Excel 8.0;HDR=YES;"""

I had the same problem. which as resolved using these steps:

1.) Click File

2.) Select "save as"

3.) Click on drop down (Save as type)

4.) Select Excel 97-2003 Workbook

5.) Click on Save button

If the file is read-only, just remove it and it should work again.

I know this is a very old post, but I can give my contribution too, on how I managed to resolve this issue.

I also use "Microsoft.ACE.OLEDB.12.0" as a Provider. When my code tried to read the XLSX file, it received the error "External table is not in the expected format." However, when I kept the file open in Excel and then the code tried to read it ... it worked.

SOLUTION: I use Office 365 with company documents and in my case, the solution was very simple, I just needed to disable the sensitivity of the document, setting it to "public". Detail: Even after saving as "public" the green check still remained marked in "Internal Use", but the problem remained solved after that.

ACE has Superceded JET

Ace Supports all Previous versions of Office

This Code works well!

        OleDbConnection MyConnection;
        DataSet DtSet;
        OleDbDataAdapter MyCommand;
        
        MyConnection = new System.Data.OleDb.OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=..\\Book.xlsx;Extended Properties=Excel 12.0;");
        MyCommand = new System.Data.OleDb.OleDbDataAdapter("select * from [Sheet1$]", MyConnection);
        DtSet = new System.Data.DataSet();
        
        MyCommand.Fill(DtSet);
        dataGridView1.DataSource = DtSet.Tables[0];
        MyConnection.Close();

Ran into the same issue and found this thread. None of the suggestions above helped except for @Smith's comment to the accepted answer on Apr 17 '13.

The background of my issue is close enough to @zhiyazw's - basically trying to set an exported Excel file (SSRS in my case) as the data source in the dtsx package. All I did, after some tinkering around, was renaming the worksheet. It doesn't have to be lowercase as @Smith has suggested.

I suppose ACE OLEDB expects the Excel file to follow a certain XML structure but somehow Reporting Services is not aware of that.

Instead of OleDb, you could use the Excel Interop and open the worksheet as read-only.

https://msdn.microsoft.com/en-us/library/microsoft.office.interop.excel.workbooks.open(v=office.15).aspx

That excel file address may have an incorrect extension. You can change the extension from xls to xlsx or vice versa and try again.

I recently had this "System.Data.OleDb.OleDbException (0x80004005): External table is not in the expected format." error occur. I was relying on Microsoft Access 2010 Runtime. Prior to the update that was automatically installed on my server on December 12th 2018 my C# code ran fine using Microsoft.ACE.OLEDB.12.0 provider. After the update from December 12th 2018 was installed I started to get the “External table is not in the expected format" in my log file.

I ditched the Microsoft Access 2010 Runtime and installed the Microsoft Access 2013 Runtime and my C# code started to work again with no "System.Data.OleDb.OleDbException (0x80004005): External table is not in the expected format." errors.

2013 version that fixed this error for me https://www.microsoft.com/en-us/download/confirmation.aspx?id=39358

2010 version that worked for me prior to the update that was automatically installed on my server on December 12th. https://www.microsoft.com/en-us/download/confirmation.aspx?id=10910 https://www.microsoft.com/en-us/download/confirmation.aspx?id=10910

I also had this error occur last month in an automated process. The C# code ran fine when I ran it debugging. I found that the service account running the code also needed permissions to the C:\Windows\Temp folder.

Working with some older code and came across this same generic exception. Very hard to track down the issue, so I thought I'd add here in case it helps someone else.

In my case, there was code elsewhere in the project that was opening a StreamReader on the Excel file before the OleDbConnection tried to Open the file (this was done in a base class).

So basically I just needed to call Close() on the StreamReader object first, then I could open the OleDb Connection successfully. It had nothing to do with the Excel file itself, or with the OleDbConnection string (which is naturally where I was looking at first).

I've had this occur on a IIS website that I host, rarely but periodically this error will popup for files that I've previously parsed just fine. Simply restarting the applicable app pool seems to resolve the issue. Not quite sure why though...

This happened to us just recently. A customer of ours was getting this error when trying to upload their excel file on our website. I could open the xlsx file fine on ms excel and don't see any irregularities with the file. I've tried all mentioned solutions in here and none worked. And i found this link Treating data as text using Microsoft.ACE.OLEDB.12.0. What worked for our case is adding IMEX=1 attribute to the connection string. So if you are using Microsoft ACE OLEDB 12.0 this might help fix your issue. Hope this helps.

<add name="ExcelTextConnection" connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 12.0;HDR={1};IMEX=1'" />