source: stable/HeuristicLab.ExtLibs/HeuristicLab.EPPlus/4.0.3/EPPlus-4.0.3/FormulaParsing/Excel/Functions/Math/CountBlank.cs

using OfficeOpenXml.FormulaParsing.Excel.Functions.Logical;
using OfficeOpenXml.FormulaParsing.ExpressionGraph;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace OfficeOpenXml.FormulaParsing.Excel.Functions.Math
{
    public class CountBlank : ExcelFunction
    {
        public override CompileResult Execute(IEnumerable<FunctionArgument> arguments, ParsingContext context)
        {
            ValidateArguments(arguments, 1);
            var arg = arguments.First();
            if(!arg.IsExcelRange)throw new InvalidOperationException("CountBlank only support ranges as arguments");
            var result = arg.ValueAsRangeInfo.GetNCells();
            foreach (var cell in arg.ValueAsRangeInfo)
            {
                if (!(cell.Value == null || cell.Value == string.Empty))
                {
                    result--;
                }
            }
            return CreateResult(result, DataType.Integer);
        }
    }
}