I need that when I send an email through Outlook using code written in C# it is sent with the email signature – Artificial Intelligence

    private void btnEnviar_Click(object sender, EventArgs e)
    {
        try
        {
            // Crear una instancia de Outlook
            Outlook.Application outlookApp = new Outlook.Application();

            // Crear un objeto de correo electrónico
            Outlook.MailItem mailItem = (Outlook.MailItem)outlookApp.CreateItem(Outlook.OlItemType.olMailItem);

            // Obtener la firma del correo electrónico
            string signature = GetOutlookSignature();

            // Establecer la firma en el correo electrónico
            mailItem.HTMLBody = signature + "<br><br>";

            // Establecer los campos del correo electrónico
            mailItem.To = "[email protected]";
            mailItem.Subject = "Asunto del correo electrónico";
            mailItem.Body = "Cuerpo del correo electrónico";

            if (lstAdjuntos.Items.Count != 0)
            {
                foreach (string filePath in lstAdjuntos.Items)
                {
                    // Adjuntar el archivo al objeto MailItem
                    mailItem.Attachments.Add(@filePath.ToString());
                }
            }

            // Enviar el correo electrónico
            mailItem.Send();

            // Liberar recursos
            System.Runtime.InteropServices.Marshal.ReleaseComObject(mailItem);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(outlookApp);
        }
        catch (Exception)
        {
            throw;
        }
    }

The code that I share already sends the email but it is sent without the signature, which I already have configured in Outlook, well, the button code also uses the following method to obtain the signature.

    public static string GetOutlookSignature()
    {
        // Obtener la ruta de la carpeta de firmas de Outlook
        string appDataPath = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
        string signatureFolder = Path.Combine(appDataPath, "Microsoft\Signatures");

        // Obtener la firma predeterminada de Outlook
        string signatureFile = Path.Combine(signatureFolder, "default.htm");

        if (File.Exists(signatureFile))
        {
            // Leer el contenido del archivo de firma
            string signature = File.ReadAllText(signatureFile, Encoding.UTF8);

            // Reemplazar las rutas absolutas de las imágenes por rutas relativas
            if (signature.Contains("<img"))
            {
                string baseFolder = signatureFolder;
                Regex regex = new Regex("src=["']([^"']*)["']", RegexOptions.IgnoreCase);
                MatchCollection matches = regex.Matches(signature);

                foreach (Match match in matches)
                {
                    string absolutePath = match.Groups[1].Value;

                    if (absolutePath.StartsWith("file://"))
                    {
                        absolutePath = absolutePath.Substring(7);
                    }

                    if (absolutePath.StartsWith("/"))
                    {
                        absolutePath = absolutePath.Substring(1);
                    }

                    string relativePath = absolutePath.Replace(baseFolder, ".");
                    signature = signature.Replace(absolutePath, relativePath);
                }
            }

            return signature;
        }
        else
        {
            // No se encontró la firma predeterminada
            return string.Empty;
        }
    }

Library used:

using Outlook = Microsoft.Office.Interop.Outlook;

I am not an advanced programmer yet and I have helped myself from artificial intelligence to get that function that gets the signature but it didn’t really help me, thanks for the help in advance.