c# – Why is the OleDbDataAdapter.Fill() extremely slow?

I am trying to build an application that will read through an excel files (.xlsx, .xls). Unfortunately, the OleDbDataAdapter.Fill() performance is surprisingly bad. I takes up to 2 minutes to read one record from the file.

More info about the file:

1. Size – 257MB
2. Columns – 104
3. Rows – 1 000 000

Code I am currently using to read the file:

    string conStr = string.Empty;
    string strQuery = string.Empty;
    switch (extension)
    {
        case ".xls": //Excel 97-03
            conStr = @"Provider=Microsoft.Jet.OleDb.12.0;Data Source=" + file_source + ";Extended Properties='Excel 8.0;HDR=YES;IMEX=1;';";
            strQuery = "SELECT " + col_no + " * FROM [" + workbook + "] ";
            break;

        case ".xlsx": //Excel 07
            //connection string to connect to the xlsx file
            conStr = @"Provider=Microsoft.Ace.OleDb.12.0;Data Source=" + file_source + ";Extended Properties='Excel 12.0 Xml;HDR=YES;IMEX=1;';";
            strQuery = "SELECT " + col_no + " * FROM [" + workbook + "] ";
            break;
    }
    DataTable tbl = new DataTable();
    OleDbDataAdapter ada = new OleDbDataAdapter(strQuery, conStr);
    ada.Fill(tbl);
    ada.Dispose();

    return tbl;

Your help would be greatly appreciated!

Thanks!

Tags: c#c#