在MVC控制器中，相同的string.replace（）具有两种不同的含义

Question

I'm trying to create something like the bool system stack overflow have in mvc controller. The code under is working perfect if i change the last or first dobbel star to something else like /*, but what if i want both to be the same? like first time ** will be < b> and next time ** will be < /b>.

[HttpPost]
[ValidateInput(false)]
public ActionResult Comment(Models.CommentModel s)
    {

        StringBuilder sbComments = new StringBuilder();
        sbComments.Append(HttpUtility.HtmlEncode(s.comment));

        sbComments.Replace("**", "<b>");
        sbComments.Replace("**", "</b>");
        sbComments.Replace("&lt;b&gt;", "<b>");
        sbComments.Replace("&lt;/b&gt;", "</b>");

        s.comment = sbComments.ToString();

        var db = new WebApplication1.Models.ApplicationDbContext();

        if (ModelState.IsValid)
        {  
            db.Comments.Add(s);
            db.SaveChanges();
            return RedirectToAction("Comment");
        }
        return View(s);
    }

My solution thanks to baiyangcao`s answer:

Regular expression might look complex, but it's not that hard to understand. This site http://regexr.com/ helpet me alot to understand this.

public ActionResult Comment(Models.CommentModel s)
    {
        Regex fat = new Regex(@"\*\*(.*?)\*\*");
        Regex italic = new Regex(@"_(.*?)_");
        Regex largeText = new Regex(@"#(.*?)#");

        s.kommentar = HttpUtility.HtmlEncode(s.comment);

        s.comment = largeText.Replace(s.comment, "<h1>$1</h1>");
        s.comment = fat.Replace(s.comment, "<b>$1</b>");
        s.comment = italic.Replace(s.comment, "<i>$1</i>");

        //this is the database I am adding my comments to
        var db = new WebApplication1.Models.ApplicationDbContext();

        if (ModelState.IsValid)
        {    
            db.Comments.Add(s);
            db.SaveChanges();
            return RedirectToAction("Comment");
        }
        return View(s);
    }

can't find Regex() ? Remember to add using System.Text.RegularExpressions; library on top of your page.

Answer 1

You can use this extension:

public static string replaceHipHip(this string text, string old, string hip, string hop)
{
    var result = new StringBuilder();
    bool b = true;
    int i = 0;
    while(i>=0)
    {
        int j = text.IndexOf(old, i);
        if (j == -1)
        {
            result.Append(text.Substring(i));
            break;
        }
        else
        {
            result.Append(text.Substring(i, j - i));
            if (b)
                result.Append(hip);
            else
                result.Append(hop);

            b ^= true;
            i = j+old.Length;
        }
    }
    return result.ToString();
}

Then your can write:

string text = "Hello **this** is a **dummy** text";
Console.WriteLine(text.replaceHipHip("**", "<b>", "</b>"));

Which outputs:

Hello is a text

Answer 2

You can try use regular expression to do the replacement, like this:

Regex regexb = new Regex("\*\*(.*?)\*\*");
string comment = regexb.Replace(HttpUtility.HtmlEncode(s.comment), "<b>$1</b>");

Hope this can help