Sorry for the delay in responding.
1) Here is the usage snippet for entering array formulas
mySheet.Range["A1"].Number = 1;
mySheet.Range["A2"].Number = 2;
mySheet.Range["A3"].Number = 3;
mySheet.Range["A4"].Number = 4;
mySheet.Range["B1"].Number = 1;
mySheet.Range["B2"].Number = 2;
mySheet.Range["B3"].Number = 3;
mySheet.Range["B4"].Number = 5;
mySheet.Range["C1"].FormulaArray = "SUM(IF(A1:A4=B1:B4,1,0))";
I tested the above snippet using version 18.104.22.168[Will be available for download later today]and it worked fine. The value in cell C1 was 3.
2) Here is the code snippet that I had used to test the your sample file
MessageBox.Show("B2 is Blank");
The result was
B2 is not blank and the FormulaArray value in B2 was
''10 + first'' which is the correct value.
However I did see a but that caused the spreadsheet generated to crash when opened using MS Excel. I have filed a bug report with the development team and it should be addressed shortly. You can track the current status here
Please let me know if you have any questions.
>Although I planned to implement read/write of xls array formulas this week, I am failing using ExcelRW 22.214.171.124.
>Attached is a "simple" xls example of array calculations (using named ranges which probably don''t work well in my version either).
>When I try to read this file in, I get a blowup when checking for B2.IsBlank. And when I check the range B2:D2, I get nothing for Formula and FormulaArray. (yes, I can read/write formulas for cells, and can read/write named ranges for a range of cells, but have not been successful in reading nor writing array formulas)
>Please show me how to read AND write such an xls using your system. I have given you months of advanced notice of my intention, but have received no samples, nor do I believe ExcelRW is ready for this.