How to remove the
tag in my html string using HtmlAgilityPack in C#?

It's as easy as:

• loading the HTML fragment into an Agility Pack HtmlDocument
• getting all <br /> tags using the "//br" xpath expression
• removing the tags obtained at the previous step using the Remove() method
• inspecting the result in the DocumentNode.OuterHtml property

Here it is in code:

const string htmlFragment =
    @"<p class=""Normal-P"" style=""direction: ltr; unicode-bidi: normal;"">" +
    @"<span class=""Normal-H"">sample<br/></span>" +
    @"<span class=""Normal-H"">texting<br></span></p> ";

var document = new HtmlAgilityPack.HtmlDocument();
document.LoadHtml(htmlFragment);

foreach (var brTag in document.DocumentNode.SelectNodes("//br"))
    brTag.Remove();

Console.WriteLine(document.DocumentNode.OuterHtml);