Why does Html.ActionLink render "?Length=4" - asp.net-mvc

Question

I'm VERY confused as to why this code
Html.ActionLink("About", "About", "Home", new { hidefocus = "hidefocus" })
results in this link:
<a hidefocus="hidefocus" href="/Home/About?Length=4">About</a>
The hidefocus part is what I was aiming to achieve, but where does the ?Length=4 come from?

Answer 1

The Length=4 is coming from an attempt to serialize a string object. Your code is running this ActionLink method:
public static string ActionLink(this HtmlHelper htmlHelper, string linkText, string actionName, object routeValues, object htmlAttributes)
This takes a string object "Home" for routeValues, which the MVC plumbing searches for public properties turning them into route values. In the case of a string object, the only public property is Length, and since there will be no routes defined with a Length parameter it appends the property name and value as a query string parameter. You'll probably find if you run this from a page not on HomeController it will throw an error about a missing About action method. Try using the following:
Html.ActionLink("About", "About", new { controller = "Home" }, new { hidefocus = "hidefocus" })

Answer 2

The way I solved this is was adding a null to the fourth parameter before the anonymous declaration (new {}) so that it uses the following method overload: (linkText, actionName, controllerName, routeValues, htmlAttributes):
Html.ActionLink("About", "About", "Home", null, new { hidefocus = "hidefocus" })

Answer 3

You forgot to add the HTMLAttributes parm.
This will work without any changes:
Html.ActionLink("About", "About", "Home", new { hidefocus = "hidefocus" },null)

Answer 4

The parameters to ActionLink are not correct, it's attempting to use the "Home" value as a route value, instead of the anonymous type.
I believe you just need to add new { } or null as the last parameter.
EDIT: Just re-read the post and realized you'll likely want to specify null as the second last parameter, not the last.

Answer 5

Html.ActionLink("About", "About", "Home", new { hidefocus = "hidefocus" }, new { })
This will take the overload:
string linkText, string actionName, string controllerName, Object routeValues, Object htmlAttributes

Answer 6

Just remove "Home" (name of the controller) so that the code would be:
Html.ActionLink("About", "About", new { hidefocus = "hidefocus" })

Answer 7

Kindly use right overloaded method with five (5) parameters. Example:
#using (#Ajax.BeginForm("Register", "Account", null,
new AjaxOptions
{
HttpMethod = "POST",
OnSuccess = "OnSuccess",
OnFailure = "OnFailure",
OnBegin = "OnBegin",
OnComplete = "OnComplete"
}, new { #class = "form-login" }))

Answer 8

This worked fine
#Html.ActionLink("Informationen", "About", "Home", new { area = "" }, new { #class = "nav-link" })
added new { area = "" }.

Answer 9

As Jonathon Watney pointed out in a comment, this also goes for
Html.BeginForm()
methods. In my case, I was in a Create.cshtml targeting the post request of the corresponding controller + Create action and had
using (Html.BeginForm("Create")) {
#Html.AntiForgeryToken()
...
}
which was adding the querystring "?Length=6" to the form action when rendered. Hinted by roryf's approved answer and realizing the string length of "Create" is 6, I finally solved this by removing the explicit action specification:
using (Html.BeginForm()) {
#Html.AntiForgeryToken()
...
}

Answer 10

With attribute names:
#Html.ActionLink(linkText: "SomeText", actionName: "SomeAction", controllerName: "SomeControllerName", routeValues: new { parameterName = parameterValue}, htmlAttributes: null)

Answer 11

Perhaps others had the same issue and need to supply a class value via HTMLAttributes parm.
Here's my solution:
#Html.ActionLink("About", "About", new { controller = "Home", area = "" }, new { hidefocus = "hidefocus", #class = "nav-item nav-link" })

Answer 12

Search for an answer to my question landed me here, basically it's the selection of correct overload of #Html.ActionLink
which matters.
I was selecting an overload which didn't exist, (without the last null), and MVC had no such overload, resulting in a false URL something like the OP mentioned.
A personal note: you can use anonymous types doesn't mean you can use any of the overloads- which do not exist? - make certain: it has to be defined!
- Came here in times of MVC 5.2