How to correctly encode MailTo links in ASP.NET MVC?

asp.net-mvc, c#, mailto, url-encoding

Solution

I know this is a little old, but I came across this when I was trying to figure out the best way to encode mailto links. I've found the best way is use `Uri.EscapeDataString` for each parameter and then encode the entire attribute thing using HttpUtility.HtmlAttributeEncode:

HttpUtility.HtmlAttributeEncode(
    String.Format("mailto:?subject={0}&body={1}", 
        Uri.EscapeDataString(subject), 
        Uri.EscapeDataString(body)))

`HttpUtility.UrlEncode` and `HttpUtility.UrlEncodeUnicode` do not correctly encode spaces -- they become plus signs ("+") which then show up as plus signs in the subject line/body/etc. `HttpUtility.UrlPathEncode` seems to fix that problem, but doesn't properly encode other characters like ?, #, and /. `Uri.EscapedDataString` seems to be the only method that properly encodes all of these characters. I imagine `Uri.HexEscape` would work equally as well, but it seems like that might be overkill.

Caveat: I haven't tested this with even a remotely wide variety of browsers and email clients

Problem

I have the following mailto link on an ASP.NET MVC 5 application: ``` <a rel="nofollow" href="@( String.Format("mailto:?subject={0}&amp;body={1}", "The title", "The description" + "%0D%0A" + "http://theurl.xyz")"> share by email </a> ``` This is not validating on HTML Validator. I get the error: Bad value mailto:?subject=The subject&body=This is the url:%0D%0Ahttp://localhost:8580/home for attribute href on element a: Whitespace in query component. Use %20 in place of spaces. I tried encoding using `HttpUtility.UrlEncode` but when I open the email I get "+" signs and others in the subject and body and I am not able to solve that.

Original source