merge pdf pages using pdfsharp in csharp

main.cs
using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;

// List of input PDF files to be merged
List<string> inputPdfFiles = new List<string>();
inputPdfFiles.Add("input1.pdf");
inputPdfFiles.Add("input2.pdf");
inputPdfFiles.Add("input3.pdf");

// Output PDF file
string outputPdfFile = "output.pdf";

// Merge PDFs
using (PdfDocument outputPdf = new PdfDocument())
{
    foreach (string inputPdfFile in inputPdfFiles)
    {
        using (PdfDocument inputPdf = PdfReader.Open(inputPdfFile, PdfDocumentOpenMode.Import))
        {
            int pageCount = inputPdf.PageCount;
            for (int i = 0; i < pageCount; i++)
            {
                // Append each page from input PDF to output PDF
                PdfPage page = inputPdf.Pages[i];
                outputPdf.AddPage(page);
            }
        }
    }
    // Save output PDF file
    outputPdf.Save(outputPdfFile);
}
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