Error on importing Excel data into a datatable

Below is the function I used. But I receive the error message:

external table not in the expected format

As a solution provided at different sites I used it as commented below but I receive the same error. Any suggestions?

public DataTable exceldata(string pathName, string sheetName)
{
    DataTable tbContainer = new DataTable();
    string strConn = string.Empty;
    if (string.IsNullOrEmpty(sheetName)) { sheetName = "Sheet1"; }
    FileInfo file = new FileInfo(pathName);
    if (!file.Exists)
    {
        throw new Exception("Error, file doesn't exists!");
    }
    string extension = file.Extension;
    switch (extension)
    {
        case ".xls":
            strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathName + ";Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'";
            // strConn = @"Data Source="+ pathName + ";Provider=Microsoft.ACE.OLEDB.12.0; Extended Properties=Excel 12.0;";
            break; Solution provided
        case ".xlsx":
            strConn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + pathName + ";Extended Properties='Excel 12.0;HDR=Yes;IMEX=1;'";
            //  strConn = @"Data Source="+ pathName + ";Provider=Microsoft.ACE.OLEDB.12.0; Extended Properties=Excel 12.0;"; Solution provided

            break;
        default:
            strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathName + ";Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'";
            break;
    }
    OleDbConnection cnnxls = new OleDbConnection(strConn);
    OleDbDataAdapter oda = new OleDbDataAdapter(string.Format("select * from [{0}$]", sheetName), cnnxls);
    DataSet ds = new DataSet();
    oda.Fill(tbContainer);
    return tbContainer;
}