The 'Microsoft.Jet.OLEDB.4.0' provider is not registered

If you face consistent compatibility issues, consider using a library like EPPlus or ClosedXML for Excel file operations. These libraries avoid the dependency on OLEDB and are more reliable for modern applications.

using OfficeOpenXml;

var package = new ExcelPackage(new FileInfo("path-to-your-file.xlsx"));
var worksheet = package.Workbook.Worksheets[0];

for (int row = 1; row <= worksheet.Dimension.End.Row; row++)
{
    for (int col = 1; col <= worksheet.Dimension.End.Column; col++)
    {
        Console.WriteLine(worksheet.Cells[row, col].Text);
    }
}

Replace Microsoft.Jet.OLEDB.4.0 with Microsoft.ACE.OLEDB.12.0 or Microsoft.ACE.OLEDB.16.0, which support both .xls and .xlsx files. Update your connection string as follows:

string connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=yourFilePath;Extended Properties=\"Excel 12.0 Xml;HDR=YES;IMEX=1\"";

• Provider=Microsoft.ACE.OLEDB.12.0: Uses the ACE OLEDB driver to access Excel files.
• Data Source=yourFilePath: Path to your Excel file.
• Excel 12.0 Xml: Specifies .xlsx format.
• HDR=YES: Indicates that the first row in Excel contains headers.
• IMEX=1: Treats all data as text to avoid type conversion issues.

Also If your application is running in IIS:

1. Open IIS Manager.
2. Go to Application Pools.
3. Select your application pool and click Advanced Settings.
4. Set Enable 32-Bit Applications to True (if using 32-bit Access Database Engine).