The CalculationMode property specifies the calculation mode for all formulas in the workbook. The CalculationMode enumeration provides three options: Manual (you manually perform the calculation), Auto (the calculation is automatically performed), or AutoNoTable (the calculation is performed except on tables).

To set the calculation mode, follow these steps:

1. Add a reference to C1.WPF.Excel.dll or C1.Silverlight.Excel.dll and create a C1XLBook.

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   // Create a new workbook C1XLBook book = new C1XLBook();

2. Add a simple formula using the following code:

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   XLSheet sheet = book.Sheets[0]; // simple formula sheet[7, 0].Value = "Formula: 5!"; sheet[7, 1].Value = 122; sheet[7, 1].Formula = "1*2*3*4*5"; book.CalculationMode = CalculationMode.Auto;

3. Save and open the .xlsx file.

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   // Save and open the file book.Save(@"C:\test.xlsx"); System.Diagnostics.Process.Start(@"C:\test.xlsx");

   Notice that the value for the cell in (7,1) is 120, or the total of 1*2*3*4*5, not 122, since we set the CalculationMode to Auto.