Does C# have an equivalent to JavaScript's encodeURIComponent()?

Question

In JavaScript:

encodeURIComponent("©√") == "%C2%A9%E2%88%9A"

Is there an equivalent for C# applications? For escaping HTML characters I used:

txtOut.Text = Regex.Replace(txtIn.Text, @"[\u0080-\uFFFF]",
    m => @"&#" + ((int)m.Value[0]).ToString() + ";");

But I'm not sure how to convert the match to the correct hexadecimal format that JS uses. For example this code:

txtOut.Text = Regex.Replace(txtIn.Text, @"[\u0080-\uFFFF]",
    m => @"%" + String.Format("{0:x}", ((int)m.Value[0])));

Returns "%a9%221a" for "©√" instead of "%C2%A9%E2%88%9A". It looks like I need to split the string up into bytes or something.

Edit: This is for a windows app, the only items available in System.Web are: AspNetHostingPermission, AspNetHostingPermissionAttribute, and AspNetHostingPermissionLevel.

score 276 · Accepted Answer · edited Dec 28 '18 at 19:26

276

Uri.EscapeDataString or HttpUtility.UrlEncode is the correct way to escape a string meant to be part of a URL.

Take for example the string "Stack Overflow":

HttpUtility.UrlEncode("Stack Overflow") --> "Stack+Overflow"
Uri.EscapeUriString("Stack Overflow") --> "Stack%20Overflow"
Uri.EscapeDataString("Stack + Overflow") --> Also encodes "+" to "%2b" ---->Stack%20%2B%20%20Overflow

Only the last is correct when used as an actual part of the URL (as opposed to the value of one of the query string parameters)

edited Dec 28 '18 at 19:26

answered Dec 29 '10 at 00:21

Steve

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The main issue I was having was not having a reference to System.Web in my solution, but I wasn't aware of EscapeUriString, thanks! – travis Jan 03 '11 at 16:29
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In contrast to encodeURIComponent(), Uri.EscapeUriString() doesn't encode "+" to "%2b". Use Uri.EscapeDataString() instead. – jwaliszko Apr 30 '12 at 10:17
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Use WebUtility instead of HttpUtility to avoid having to reference System.Web. HttpUtility doesn't exist in .NET Core. – Steven De Kock Dec 31 '15 at 01:15
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@Steve Would you consider making your last paragraph bold? It seems to be the most important thing to know on this page, and it needs more visibility. – Timo Aug 25 '16 at 15:45
Also see this answer for more explanation on the difference between Uri.EscapeUriString and Uri.EscapeDataString: https://stackoverflow.com/questions/4396598/whats-the-difference-between-escapeuristring-and-escapedatastring – Jason Mar 16 '17 at 16:12
See this answer for more explanation on the difference between HttpUtility.UrlEncode and HttpUtility.UrlPathEncode https://stackoverflow.com/questions/4145823/httpserverutility-urlpathencode-vs-httpserverutility-urlencode – Jason Mar 16 '17 at 16:30
`UrlPathEncode` and `EscapeUriString` do not encode ampersand `&` but `Uri.EscapeDataString` and `HttpUtility.UrlEncode()` do – nothingisnecessary Mar 28 '17 at 18:52
Kudos to Steve for providing this excellent answer and Tim for the edited version. This work well and save my nerves after a very long search. To all of you who always contribute to this very useful platform, I say thank you! – omostan Apr 08 '22 at 08:59
`EscapeUriString` has been marked as absolete starting from .NET 6 because it can corrupt the Uri string in some cases. Use `EscapeDataString` instead. See: https://learn.microsoft.com/en-us/dotnet/fundamentals/syslib-diagnostics/syslib0013 – H. Pauwelyn Jun 19 '23 at 13:38

score 22 · Answer 2 · edited Dec 29 '10 at 05:13

22

HttpUtility.HtmlEncode / Decode
HttpUtility.UrlEncode / Decode

You can add a reference to the System.Web assembly if it's not available in your project

edited Dec 29 '10 at 05:13

Gabe

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answered Sep 17 '08 at 19:06

David Thibault

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I should've been more specific: This is for a windows app, the only items available in System.Web are: AspNetHostingPermission, AspNetHostingPermissionAttribute, and AspNetHostingPermissionLevel. – travis Sep 17 '08 at 19:15
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You can add a reference to the System.Web assembly – David Thibault Sep 17 '08 at 19:18
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HtmlEncoding is an entirely different thing. UrlEncode is a non-sensical API which should never be used. It doesn't make sense to encode an entire URL (unless you actually want to encode its value to use as a parameter - but that's not what this does). The point of encoding/escaping is that you're conveying that a reserved character should be passed through without its usual meaning (e.g. that ? identifies the query, or & separates query parameters). This requires knowledge that UrlEncode does not and cannot have. – Brandon Paddock Apr 15 '16 at 19:53

score 19 · Answer 3 · edited Nov 14 '13 at 03:39

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I tried to do full compatible analog of javascript's encodeURIComponent for c# and after my 4 hour experiments I found this

c# CODE:

string a = "!@#$%^&*()_+ some text here али мамедов баку";
a = System.Web.HttpUtility.UrlEncode(a);
a = a.Replace("+", "%20");

the result is: !%40%23%24%25%5e%26*()_%2b%20some%20text%20here%20%d0%b0%d0%bb%d0%b8%20%d0%bc%d0%b0%d0%bc%d0%b5%d0%b4%d0%be%d0%b2%20%d0%b1%d0%b0%d0%ba%d1%83

After you decode It with Javascript's decodeURLComponent();

you will get this: !@#$%^&*()_+ some text here али мамедов баку

Thank You for attention

edited Nov 14 '13 at 03:39

dana

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answered Feb 04 '11 at 20:39

Ali Mamedov

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Works, but you can simply use `Uri.EscapeDataString("!@#$%^&*()_+ some text here али мамедов баку")` instead. – mklement0 Sep 18 '16 at 16:06
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Actually, `Uri.EscapeDataString` encodes the characters '(' and ')' while `HttpUtility.UrlEncode` does not. – Øystein Kolsrud Sep 05 '19 at 08:45

score 13 · Answer 4 · answered Mar 06 '09 at 18:46

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System.Uri.EscapeUriString() didn't seem to do anything, but System.Uri.EscapeDataString() worked for me.

answered Mar 06 '09 at 18:46

Echilon

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score 10 · Answer 5 · answered Jun 10 '13 at 08:51

For a Windows Store App, you won't have HttpUtility. Instead, you have:

For an URI, before the '?':

System.Uri.EscapeUriString("example.com/Stack Overflow++?")
- -> "example.com/Stack%20Overflow++?"

For an URI query name or value, after the '?':

System.Uri.EscapeDataString("Stack Overflow++")
- -> "Stack%20Overflow%2B%2B"

For a x-www-form-urlencoded query name or value, in a POST content:

System.Net.WebUtility.UrlEncode("Stack Overflow++")
- -> "Stack+Overflow%2B%2B"

Billy Jo · Answer 6 · 2008-09-17T19:23:42.773

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Try Server.UrlEncode(), or System.Web.HttpUtility.UrlEncode() for instances when you don't have access to the Server object. You can also use System.Uri.EscapeUriString() to avoid adding a reference to the System.Web assembly.

edited Sep 17 '08 at 19:23

answered Sep 17 '08 at 19:07

Billy Jo

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Uri.EscapeUriString() didn't do anything for me, but I was able to properly url-encode the strings using Uri.EscapeDataString() – Toland Hon Feb 13 '14 at 01:15
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@TolandHon: Indeed. The reason is that `Uri.EscapeUriString()` corresponds to JavaScript's `encodeURI()` - which preserves URI-reserved chars. such as `/`, `&`, ... as-is (plus `#`), whereas - as you've discovered, it is `Uri.EscapeDataString()` that corresponds to JavaScript's `encodeURIComponent()`. – mklement0 Sep 18 '16 at 20:42

Mitchel Sellers · Answer 7 · 2008-09-17T19:24:44.597

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You can use the Server object in the System.Web namespace

Server.UrlEncode, Server.UrlDecode, Server.HtmlEncode, and Server.HtmlDecode.

Edit: poster added that this was a windows application and not a web one as one would believe. The items listed above would be available from the HttpUtility class inside System.Web which must be added as a reference to the project.

edited Sep 17 '08 at 19:24

answered Sep 17 '08 at 19:06

Mitchel Sellers

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The Server object is inaccessible from a windows app – travis Sep 17 '08 at 19:21

Does C# have an equivalent to JavaScript's encodeURIComponent()?

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