I have a very simple asp:textbox with the multiline attribute enabled. I then accept just text, with no markup, from the textbox. Is there a common method by which line breaks and returns can be converted to <p> and <br/> tags?
I'm not looking for anything earth shattering, but at the same time I don't just want to do something like:
html.Insert(0, "<p>");
html.Replace(Enviroment.NewLine + Enviroment.NewLine, "</p><p>");
html.Replace(Enviroment.NewLine, "<br/>");
html.Append("</p>");
The above code doesn't work right, as in generating correct html, if there are more than 2 line breaks in a row. Having html like <br/></p><p> is not good; the <br/> can be removed.
I know this is old, but I couldn't find anything better after some searching, so here is what I'm using:
public static string TextToHtml(string text)
{
text = HttpUtility.HtmlEncode(text);
text = text.Replace("\r\n", "\r");
text = text.Replace("\n", "\r");
text = text.Replace("\r", "<br>\r\n");
text = text.Replace(" ", " ");
return text;
}
If you can't use HttpUtility for some reason, then you'll have to do the HTML encoding some other way, and there are lots of minor details to worry about (not just <>&).
HtmlEncode only handles the special characters for you, so after that I convert any combo of carriage-return and/or line-feed to a BR tag, and any double-spaces to a single-space plus a NBSP.
Optionally you could use a PRE tag for the last part, like so:
public static string TextToHtml(string text)
{
text = "<pre>" + HttpUtility.HtmlEncode(text) + "</pre>";
return text;
}
Your other option is to take the text box contents and instead of trying for line a paragraph breaks just put the text between PRE tags. Like this:
<PRE>
Your text from the text box...
and a line after a break...
</PRE>
Depending on exactly what you are doing with the content, my typical recommendation is to ONLY use the <br /> syntax, and not to try and handle paragraphs.
How about throwing it in a <pre> tag. Isn't that what it's there for anyway?
I know this is an old post, but I've recently been in a similar problem using C# with MVC4, so thought I'd share my solution.
We had a description saved in a database. The text was a direct copy/paste from a website, and we wanted to convert it into semantic HTML, using <p> tags. Here is a simplified version of our solution:
string description = getSomeTextFromDatabase();
foreach(var line in description.Split('\n')
{
Console.Write("<p>" + line + "</p>");
}
In our case, to write out a variable, we needed to prefix # before any variable or identifiers, because of the Razor syntax in the ASP.NET MVC framework. However, I've shown this with a Console.Write, but you should be able to figure out how to implement this in your specific project based on this :)
Combining all previous plus considering titles and subtitles within the text comes up with this:
public static string ToHtml(this string text)
{
var sb = new StringBuilder();
var sr = new StringReader(text);
var str = sr.ReadLine();
while (str != null)
{
str = str.TrimEnd();
str.Replace(" ", " ");
if (str.Length > 80)
{
sb.AppendLine($"<p>{str}</p>");
}
else if (str.Length > 0)
{
sb.AppendLine($"{str}</br>");
}
str = sr.ReadLine();
}
return sb.ToString();
}
the snippet could be enhanced by defining rules for short strings
I understand that I was late with the answer for 13 years)
but maybe someone else needs it
sample line 1 \r\n
sample line 2 (last at paragraph) \r\n\r\n [\r\n]+
sample line 3 \r\n
Example code
private static Regex _breakRegex = new("(\r?\n)+");
private static Regex _paragrahBreakRegex = new("(?:\r?\n){2,}");
public static string ConvertTextToHtml(string description) {
string[] descrptionParagraphs = _paragrahBreakRegex.Split(description.Trim());
if (descrptionParagraphs.Length > 0)
{
description = string.Empty;
foreach (string line in descrptionParagraphs)
{
description += $"<p>{line}</p>";
}
}
return _breakRegex.Replace(description, "<br/>");
}
Related
I want to find all the instagram urls within a string, and replace them with the embed url.
But I'm keen on performance, as this could be 5 to 20 posts each anything up to 6000 characters with an unknown amount of instagram urls in which need converting.
Url examples (Could be any of these in each string, so would need to match all)
http://instagram.com/p/xPnQ1ZIY2W/?modal=true
http://instagram.com/p/xPnQ1ZIY2W/
http://instagr.am/p/xPnQ1ZIY2W/
And this is what I need to replace them with (An embedded version)
<img src="http://instagram.com/p/xPnQ1ZIY2W/media/?size=l" class="instagramimage" />
I was thinking about going for regex? But is this the quickest and most performant way of doing this?
Any examples greatly appreciated.
Something like:
Regex reg = new Regex(#"http://instagr\.?am(?:\.com)?/\S*");
Edited regex. However i would combine this with a stringreader and do it line by line. Then put the string (modified or not) into a stringbuilder:
string original = #"someotherText http://instagram.com/p/xPnQ1ZIY2W/?modal=true some other text
some other text http://instagram.com/p/xPnQ1ZIY2W/ some other text
some other text http://instagr.am/p/xPnQ1ZIY2W/ some other text";
StringBuilder result = new StringBuilder();
using (StringReader reader = new StringReader(original))
{
while (reader.Peek() > 0)
{
string line = reader.ReadLine();
if (reg.IsMatch(line))
{
string url = reg.Match(line).ToString();
result.AppendLine(reg.Replace(line,string.Format("<img src=\"{0}\" class=\"instagramimage\" />",url)));
}
else
{
result.AppendLine(line);
}
}
}
Console.WriteLine(result.ToString());
You mean like this?
class Program
{
private static Regex reg = new Regex(#"http://instagr\.?am(?:\.com)?/\S*", RegexOptions.Compiled);
private static Regex idRegex = new Regex(#"(?<=p/).*?(?=/)",RegexOptions.Compiled);
static void Main(string[] args)
{
string original = #"someotherText http://instagram.com/p/xPnQ1ZIY2W/?modal=true some other text
some other text http://instagram.com/p/xPnQ1ZIY2W/ some other text
some other text http://instagr.am/p/xPnQ1ZIY2W/ some other text";
StringBuilder result = new StringBuilder();
using (StringReader reader = new StringReader(original))
{
while (reader.Peek() > 0)
{
string line = reader.ReadLine();
if (reg.IsMatch(line))
{
string url = reg.Match(line).ToString();
result.AppendLine(reg.Replace(line, string.Format("<img src=\"http://instagram.com/p/{0}/media/?size=1\" class=\"instagramimage\" />", idRegex.Match(url).ToString())));
}
else
{
result.AppendLine(line);
}
}
}
Console.WriteLine(result.ToString());
}
}
A well-crafted and compiled regular expression is hard to beat, especially since you're doing replacements, not just searching, but you should test to be sure.
If the Instagram URLs are only within HTML attributes, here's my first stab at a pattern to look for:
(?<=")(https?://instagr[^">]+)
(I added a check for https as well, which you didn't mention but I believe is supported by Instagram.)
Some false positives are theoretically possible, but it will perform better than pedantically matching every legal variation of an Instagram URL. (The ">" check is just in case the HTML is missing the end quote for some reason.)
Sometimes from a 3rd party API I get malformed HTML elements returned:
olor:red">Text</span>
when I expect:
<span style="color:red">Text</span>
For my context, the text content of the HTML is more important so it does not matter if I lose surrounding tags/formatting.
What would be the best way to strip out the malformed tags such that the first example would read
Text
and the second would not change?
I recommend you to take a look at the HtmlAgilityPack, which is a very handy tool also for HTML sanitization.
Here's an approach example by using the aforementioned library:
static void Main()
{
var inputs = new[] {
#"olor:red"">Text</span>",
#"<span style=""color:red"">Text</span>",
#"Text</span>",
#"<span style=""color:red"">Text",
#"<span style=""color:red"">Text"
};
var doc = new HtmlDocument();
inputs.ToList().ForEach(i => {
if (!i.StartsWith("<"))
{
if (i.IndexOf(">") != i.Length-1)
i = "<" + i;
else
i = i.Substring(0, i.IndexOf("<"));
doc.LoadHtml(i);
Console.WriteLine(doc.DocumentNode.InnerText);
}
else
{
doc.LoadHtml(i);
Console.WriteLine(doc.DocumentNode.OuterHtml);
}
});
}
Outputs:
Text
<span style="color:red">Text</span>
Text
<span style="color:red">Text</span>
<span style="color:red">Text</span>
If you just need the content of the tags, and no information of what type of tag etc, you could use Regular Expressions:
var r = new Regex(">([^>]+)<");
var text = "olor:red\">Text</span>";
var m = r.Match(text);
This will find every inner text of each tag.
Very crudely, you could strip out all 'tags' by stripping everything before a > and keeping everything before a <.
I'm assuming you also need to consider the situation where the text your receive is without tags: e.g. Text.
In pseudo-code:
returnText = ""
loop:
gtI = text.IndexOf(">")
ltI = text.IndexOf("<")
if -1==gtI and -1==ltI:
returnText += text
we're done
if gtI==-1:
returnText += text up to position ltI
return returnText
if ltI==-1:
returnText += text after gtI
return returnText
if ltI < gtI:
returnText += textBefore ltI
text = text after ltI
loop
// gtI < ltI:
text = text after gtI
loop
It's crude and can be done much better (and faster) with a custom coded parser, but essentially the logic would be the same.
You should really be asking why the API returns only part of what you require: I can't see why it should be returning ext</span> either, which really messes you up.
First of all: Sorry for my bad English!
I know the title isn't the best English, but I don't really know how to format this question...
What I'm trying to do is reading an HTML source line by line so when it sees a given word (like http://) it copies the entire sentence so I can strip the rest an only keep the URL.
This is what I've tried:
using (var source = new StreamReader(TempFile))
{
string line;
while ((line = source.ReadLine()) != null)
{
if (line.Contains("http://"))
{
Console.WriteLine(line);
}
}
}
This works perfectly if I want to read it from an external file but it doesn't work when I want to read an string or stringbuilder, how do you read those line by line?
You can use new StringReader(theString) to do that with a string, but I question your overall strategy. That would be better done with a tool like HTML Agility Pack.
For example, here is HTML Agility Pack extracting all hyperlinks:
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(theString);
foreach(HtmlNode link in doc.DocumentElement.SelectNodes("//a[#href]")
{
HtmlAttribute att = link["href"];
Console.WriteLine(att.Value);
}
Well a string is just a string, it doesn't have any lines.
You can use something like String.Split to separate on the \r symbol.
MSDN: String.Split()
string words = "This is a list of words, with: a bit of punctuation" +
"\rand a newline character.";
string [] split = words.Split(new Char [] {'\r' });
foreach (string s in split) {
if (s.Trim() != "")
Console.WriteLine(s);
}
Firstly, you can use a StringReader.
Another option is to create a MemoryStream from the string via converting the string to a byte array first, as described in https://stackoverflow.com/a/10380166/396583
I think you can tokenize the input and check each entry for the required content.
string[] info = myStringBuilder.toString().split[' '];
foreach(var item in info) {
if(item.Contains('http://') {
//work with it
}
}
You can use a memory stream to read from.
I am using Html.Raw(Html.Encode()) to allow some of html to be allowed. For example I want bold, italic, code etc... I am not sure it's the right method, code seems pretty ugly.
Input
Hello, this text will be [b]bold[/b]. [code]alert("Test...")[/code]
Output
Code
#Html.Raw(Html.Encode(Model.Body)
.Replace(Environment.NewLine, "<br />")
.Replace("[b]", "<b>")
.Replace("[/b]", "</b>")
.Replace("[code]", "<div class='codeContainer'><pre name='code' class='javascript'>")
.Replace("[/code]", "</pre></div>"))
My Solution
I want to make it all a bit different. Instead of using BB-Tags I want to use simpler tags.For example * will stand for bold. That means if I input This text is *bold*. it will replace text to This text is <b>bold</b>.. Kinda like this website is using BTW.
Problem
To implement this I need some Regex and I have little to no experience with it. I've searched many sites, but no luck.
My implementation of it looks something like this, but it fails since I can't really replace a char with string.
static void Main(string[] args)
{
string myString = "Hello, this text is *bold*, this text is also *bold*. And this is code: ~MYCODE~";
string findString = "\\*";
int firstMatch, nextMatch;
Match match = Regex.Match(myString, findString);
while (match.Success == true)
{
Console.WriteLine(match.Index);
firstMatch = match.Index;
match = match.NextMatch();
if (match.Success == true)
{
nextMatch = match.Index;
myString = myString[firstMatch] = "<b>"; // Ouch!
}
}
Console.ReadLine();
}
To implement this I need some Regex
Ah no, you don't need Regex. Manipulating HTML with Regex could lead to some undesired effects. So you could simply use MarkDownSharp which by the way is what this site uses to safely render Markdown markup into HTML.
Like this:
var markdown = new Markdown();
string html = markdown.Transform(SomeTextContainingMarkDown);
Of course to polish this you would write an HTML helper so that in your view:
#Html.Markdown(Model.Body)
Using ASP.NET, how can I strip the HTML tags from a given string reliably (i.e. not using regex)? I am looking for something like PHP's strip_tags.
Example:
<ul><li>Hello</li></ul>
Output:
"Hello"
I am trying not to reinvent the wheel, but I have not found anything that meets my needs so far.
If it is just stripping all HTML tags from a string, this works reliably with regex as well. Replace:
<[^>]*(>|$)
with the empty string, globally. Don't forget to normalize the string afterwards, replacing:
[\s\r\n]+
with a single space, and trimming the result. Optionally replace any HTML character entities back to the actual characters.
Note:
There is a limitation: HTML and XML allow > in attribute values. This solution will return broken markup when encountering such values.
The solution is technically safe, as in: The result will never contain anything that could be used to do cross site scripting or to break a page layout. It is just not very clean.
As with all things HTML and regex:
Use a proper parser if you must get it right under all circumstances.
Go download HTMLAgilityPack, now! ;) Download LInk
This allows you to load and parse HTML. Then you can navigate the DOM and extract the inner values of all attributes. Seriously, it will take you about 10 lines of code at the maximum. It is one of the greatest free .net libraries out there.
Here is a sample:
string htmlContents = new System.IO.StreamReader(resultsStream,Encoding.UTF8,true).ReadToEnd();
HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc.LoadHtml(htmlContents);
if (doc == null) return null;
string output = "";
foreach (var node in doc.DocumentNode.ChildNodes)
{
output += node.InnerText;
}
Regex.Replace(htmlText, "<.*?>", string.Empty);
protected string StripHtml(string Txt)
{
return Regex.Replace(Txt, "<(.|\\n)*?>", string.Empty);
}
Protected Function StripHtml(Txt as String) as String
Return Regex.Replace(Txt, "<(.|\n)*?>", String.Empty)
End Function
I've posted this on the asp.net forums, and it still seems to be one of the easiest solutions out there. I won't guarantee it's the fastest or most efficient, but it's pretty reliable.
In .NET you can use the HTML Web Control objects themselves. All you really need to do is insert your string into a temporary HTML object such as a DIV, then use the built-in 'InnerText' to grab all text that is not contained within tags. See below for a simple C# example:
System.Web.UI.HtmlControls.HtmlGenericControl htmlDiv = new System.Web.UI.HtmlControls.HtmlGenericControl("div");
htmlDiv.InnerHtml = htmlString;
String plainText = htmlDiv.InnerText;
I have written a pretty fast method in c# which beats the hell out of the Regex. It is hosted in an article on CodeProject.
Its advantages are, among better performance the ability to replace named and numbered HTML entities (those like & and &203;) and comment blocks replacement and more.
Please read the related article on CodeProject.
Thank you.
For those of you who can't use the HtmlAgilityPack, .NETs XML reader is an option. This can fail on well formatted HTML though so always add a catch with regx as a backup. Note this is NOT fast, but it does provide a nice opportunity for old school step through debugging.
public static string RemoveHTMLTags(string content)
{
var cleaned = string.Empty;
try
{
StringBuilder textOnly = new StringBuilder();
using (var reader = XmlNodeReader.Create(new System.IO.StringReader("<xml>" + content + "</xml>")))
{
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Text)
textOnly.Append(reader.ReadContentAsString());
}
}
cleaned = textOnly.ToString();
}
catch
{
//A tag is probably not closed. fallback to regex string clean.
string textOnly = string.Empty;
Regex tagRemove = new Regex(#"<[^>]*(>|$)");
Regex compressSpaces = new Regex(#"[\s\r\n]+");
textOnly = tagRemove.Replace(content, string.Empty);
textOnly = compressSpaces.Replace(textOnly, " ");
cleaned = textOnly;
}
return cleaned;
}
string result = Regex.Replace(anytext, #"<(.|\n)*?>", string.Empty);
I've looked at the Regex based solutions suggested here, and they don't fill me with any confidence except in the most trivial cases. An angle bracket in an attribute is all it would take to break, let alone mal-formmed HTML from the wild. And what about entities like &? If you want to convert HTML into plain text, you need to decode entities too.
So I propose the method below.
Using HtmlAgilityPack, this extension method efficiently strips all HTML tags from an html fragment. Also decodes HTML entities like &. Returns just the inner text items, with a new line between each text item.
public static string RemoveHtmlTags(this string html)
{
if (String.IsNullOrEmpty(html))
return html;
var doc = new HtmlAgilityPack.HtmlDocument();
doc.LoadHtml(html);
if (doc.DocumentNode == null || doc.DocumentNode.ChildNodes == null)
{
return WebUtility.HtmlDecode(html);
}
var sb = new StringBuilder();
var i = 0;
foreach (var node in doc.DocumentNode.ChildNodes)
{
var text = node.InnerText.SafeTrim();
if (!String.IsNullOrEmpty(text))
{
sb.Append(text);
if (i < doc.DocumentNode.ChildNodes.Count - 1)
{
sb.Append(Environment.NewLine);
}
}
i++;
}
var result = sb.ToString();
return WebUtility.HtmlDecode(result);
}
public static string SafeTrim(this string str)
{
if (str == null)
return null;
return str.Trim();
}
If you are really serious, you'd want to ignore the contents of certain HTML tags too (<script>, <style>, <svg>, <head>, <object> come to mind!) because they probably don't contain readable content in the sense we are after. What you do there will depend on your circumstances and how far you want to go, but using HtmlAgilityPack it would be pretty trivial to whitelist or blacklist selected tags.
If you are rendering the content back to an HTML page, make sure you understand XSS vulnerability & how to prevent it - i.e. always encode any user-entered text that gets rendered back onto an HTML page (> becomes > etc).
For those who are complining about Michael Tiptop's solution not working, here is the .Net4+ way of doing it:
public static string StripTags(this string markup)
{
try
{
StringReader sr = new StringReader(markup);
XPathDocument doc;
using (XmlReader xr = XmlReader.Create(sr,
new XmlReaderSettings()
{
ConformanceLevel = ConformanceLevel.Fragment
// for multiple roots
}))
{
doc = new XPathDocument(xr);
}
return doc.CreateNavigator().Value; // .Value is similar to .InnerText of
// XmlDocument or JavaScript's innerText
}
catch
{
return string.Empty;
}
}
using System.Text.RegularExpressions;
string str = Regex.Replace(HttpUtility.HtmlDecode(HTMLString), "<.*?>", string.Empty);
You can also do this with AngleSharp which is an alternative to HtmlAgilityPack (not that HAP is bad). It is easier to use than HAP to get the text out of a HTML source.
var parser = new HtmlParser();
var htmlDocument = parser.ParseDocument(source);
var text = htmlDocument.Body.Text();
You can take a look at the key features section where they make a case at being "better" than HAP. I think for the most part, it is probably overkill for the current question but still, it is an interesting alternative.
For the second parameter,i.e. keep some tags, you may need some code like this by using HTMLagilityPack:
public string StripTags(HtmlNode documentNode, IList keepTags)
{
var result = new StringBuilder();
foreach (var childNode in documentNode.ChildNodes)
{
if (childNode.Name.ToLower() == "#text")
{
result.Append(childNode.InnerText);
}
else
{
if (!keepTags.Contains(childNode.Name.ToLower()))
{
result.Append(StripTags(childNode, keepTags));
}
else
{
result.Append(childNode.OuterHtml.Replace(childNode.InnerHtml, StripTags(childNode, keepTags)));
}
}
}
return result.ToString();
}
More explanation on this page: http://nalgorithm.com/2015/11/20/strip-html-tags-of-an-html-in-c-strip_html-php-equivalent/
Simply use string.StripHTML();