Live Razor Page Samples

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using System.ComponentModel.DataAnnotations;
using System.Threading.Tasks;

namespace Website.Pages.Support.Samples.RazorPages.Calculations
{
    public partial class FormulaEvaluationModel : PageModel
    {
        [BindProperty]
        [StringLength(50)]
        [Display(Name = "Formula")]
        public string Formula { get; set; }

        public string Result { get; set; }

        public void OnGet()
        {
            Formula = @"TEXT(STDEV(1, 2, 3, 4), ""0.00"")";
        }

        public void OnPost()
        {
            if (!ModelState.IsValid)
            {
                SetErrorMessage("Error occurred while running sample.  Please correct the errors shown below.");
                return Page();
            }

            // Create a new empty workbook and get the first sheet. 
            SpreadsheetGear.IWorkbook workbook = SpreadsheetGear.Factory.GetWorkbook();
            SpreadsheetGear.IWorksheet worksheet = workbook.Worksheets[0];

            // Evaluate the input formula.
            object result = worksheet.EvaluateValue(Formula ?? "");

            // Display the result to the user.
            if (result == null)
                Result = "Empty cell or invalid formula.";
            else if (result is SpreadsheetGear.ValueError valueError)
                Result = $"Value Error: #{valueError.ToString().ToUpper()}";
            else
                Result = $@"Result calculated from ISheet.EvaluateValue(""{Formula}""): {result}";

            return Page();
        }
    }
}