Excel – Difference between DateValue and CDate in VBA

You can use a library called ExcelLibrary. It's a free, open source library posted on Google Code:

ExcelLibrary

This looks to be a port of the PHP ExcelWriter that you mentioned above. It will not write to the new .xlsx format yet, but they are working on adding that functionality in.

It's very simple, small and easy to use. Plus it has a DataSetHelper that lets you use DataSets and DataTables to easily work with Excel data.

ExcelLibrary seems to still only work for the older Excel format (.xls files), but may be adding support in the future for newer 2007/2010 formats.

You can also use EPPlus, which works only for Excel 2007/2010 format files (.xlsx files). There's also NPOI which works with both.

There are a few known bugs with each library as noted in the comments. In all, EPPlus seems to be the best choice as time goes on. It seems to be more actively updated and documented as well.

Also, as noted by @АртёмЦарионов below, EPPlus has support for Pivot Tables and ExcelLibrary may have some support (Pivot table issue in ExcelLibrary)

Here are a couple links for quick reference:
ExcelLibrary - GNU Lesser GPL
EPPlus - GNU (LGPL) - No longer maintained
EPPlus 5 - Polyform Noncommercial - Starting May 2020
NPOI - Apache License

Here some example code for ExcelLibrary:

Here is an example taking data from a database and creating a workbook from it. Note that the ExcelLibrary code is the single line at the bottom:

//Create the data set and table
DataSet ds = new DataSet("New_DataSet");
DataTable dt = new DataTable("New_DataTable");

//Set the locale for each
ds.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;
dt.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;

//Open a DB connection (in this example with OleDB)
OleDbConnection con = new OleDbConnection(dbConnectionString);
con.Open();

//Create a query and fill the data table with the data from the DB
string sql = "SELECT Whatever FROM MyDBTable;";
OleDbCommand cmd = new OleDbCommand(sql, con);
OleDbDataAdapter adptr = new OleDbDataAdapter();

adptr.SelectCommand = cmd;
adptr.Fill(dt);
con.Close();

//Add the table to the data set
ds.Tables.Add(dt);

//Here's the easy part. Create the Excel worksheet from the data set
ExcelLibrary.DataSetHelper.CreateWorkbook("MyExcelFile.xls", ds);

Creating the Excel file is as easy as that. You can also manually create Excel files, but the above functionality is what really impressed me.

While Issun has answered your question as asked I had enough detail that I wanted to post to provide a further answer as opposed to comment.

The string versions are significantly faster ~ approx 10-30% depending on the data type from my testing over the years. While this is not normally noticeable, it is a performance difference when running on large datasets. So for me it's a no-brainer to use the string rather than variant version.

The sample below works on strings so it shows a speed advantage at the higher end of this range

I have used these functions in combination with variant arrays in both of my public addins as these programs are typically used on entire worksheets even entire workbooks

This link is an excellent reference, for your question, and well beyond

1. Comparing in vbBinaryCompare rather than vbTextCompare
2. Optimising empty strings
3. Testing before replacing
4. Using built in constants, VbNullString is faster than "", although both will miss a cell that contains ' whereas IsEmpty picks this up
5. Optimising Loops (break AND into two separate IFs to give an early escape)
6. Optimising If tests to return the most common Boolean result first rather than run through the Else path (ie a False test may be more appropriate than True)

7. Using Mid$ on the left hand side of an assignment. From hidden features of VBA

   Sub QuickTimer1()
   Dim lngRow As Long
   Dim dbTime As Double
   Dim strSample As String
   Dim strShort As String
   strSample = "random string"
   dbTime = Timer()
   For lngRow = 1 To 50000000
       strShort = Left$(strSample, 6)
   Next lngRow
   MsgBox Timer() - dbTime
   End Sub
   
   Sub QuickTimer2()
   Dim lngRow As Long
   Dim dbTime As Double
   Dim strSample As String
   Dim strShort As String
   strSample = "random string"
   dbTime = Timer()
   For lngRow = 1 To 50000000
       strShort = Left(strSample, 6)
   Next lngRow
   MsgBox Timer() - dbTime
   End Sub