using System;

using System.Linq;

using HtmlAgilityPack;

public class Program

{

    public static void Main()

    {

        var html = @"

        <p>

          <span style=""font-size: 12px""

            ><br />

            <img id=""#assinatura46969#"" style=""display: none;"">

            <br />_________________________________________________________________<br />

            <span id=""#nome46969#"" style=""display: none;""></span>

            <br />CPF:

          </span>

        </p>";

        var htmlDoc = new HtmlDocument();

        htmlDoc.LoadHtml(html);

        ExibirTagHtml(htmlDoc, $"//img[@id='#assinatura46969#']", (node) =>

        {

            node.Attributes.Add("height", "35px");

            node.Attributes.Add("src", "assinatura");

        });

        ExibirTagHtml(htmlDoc, $"//span[@id='#nome46969#']", (node) =>

        {

            node.InnerHtml = "GABRIEL DE GRANDE";

        });

        //foreach (var node in htmlDoc.DocumentNode.SelectNodes("//img[@id='#assinatura46970#']"))

        //{

        //  node.Attributes.Add("height", "50px");

        //  var height = node.Attributes["height"];

        //  string style = node.GetAttributeValue("style", "");

        //  if (!string.IsNullOrEmpty(style))

        //  {

        //      var properties = style.Split(';')

        //          .Select(p => p.Trim())

        //          .Where(p => !p.StartsWith("display", StringComparison.OrdinalIgnoreCase))

        //          .Where(p => !string.IsNullOrEmpty(p));

​

        //      if (properties.Any())

        //      {

        //          node.SetAttributeValue("style", string.Join("; ", properties));

        //      }

        //      else

        //      {

        //          node.Attributes.Remove("style");

        //      }

        //  }

            //Console.WriteLine(height);

            //imagem.Attributes["height"].Value = "50";

            //imagem.Attributes["display"].Remove();

        //}

        Console.WriteLine(htmlDoc.DocumentNode.OuterHtml);

    }

    private static void ExibirTagHtml(HtmlDocument htmlDoc, string xPath, Action<HtmlNode> acao = null)

    {

        foreach (var node in htmlDoc.DocumentNode.SelectNodes(xPath))

        {

            acao?.Invoke(node);

​

            string style = node.GetAttributeValue("style", "");

​

            if (!string.IsNullOrEmpty(style))

            {

                var properties = style.Split(';')

                    .Select(p => p.Trim())

                    .Where(p => !p.StartsWith("display", StringComparison.OrdinalIgnoreCase))

                    .Where(p => !string.IsNullOrEmpty(p));

​

                if (properties.Any())

                    node.SetAttributeValue("style", string.Join("; ", properties));

                else

                    node.Attributes.Remove("style");

            }

        }

    }

}