ValidateAntiForgeryToken breaks page - asp.net-core-mvc

Question

I have an ASP .Net Core 1.1 MVC web app. When I add the [ValidateAntiForgeryToken] decoration to my Edit/Delete/Create controllers, the pages don't load (
HTTP 400 error). Any ideas why? I read somewhere that I have to add a corresponding #HtmlHelper.AntiForgeryToken to my Views, or something like that? But not sure where to put it... However, I've also read that it's not necessary to do this anymoer in ASP .Net Core...
Here is an example of my Edit view for a "Users" controller:
#model InspectionsData.Models.User
#{
ViewData["Title"] = "Edit";
}
<h2>Edit</h2>
<form asp-action="Edit">
<div class="form-horizontal">
<h4>User</h4>
<hr />
<div asp-validation-summary="ModelOnly" class="text-danger"></div>
<div class="form-group" hidden>
<label asp-for="UserId" class="col-md-2 control-label"></label>
<div class="col-md-10">
<input asp-for="UserId" class="form-control" />
<span asp-validation-for="UserId" class="text-danger"></span>
</div>
</div>
<div class="form-group">
<label asp-for="FirstName" class="col-md-2 control-label"></label>
<div class="col-md-10">
<input asp-for="FirstName" class="form-control" />
<span asp-validation-for="FirstName" class="text-danger"></span>
</div>
</div>
<div class="form-group">
<label asp-for="LastName" class="col-md-2 control-label"></label>
<div class="col-md-10">
<input asp-for="LastName" class="form-control" />
<span asp-validation-for="LastName" class="text-danger"></span>
</div>
</div>
</div>
</form>
<div>
<a asp-action="Index">Back to List</a>
</div>
Thank you

Answer 1

You need to change your form declaration to something like the following.
<form asp-controller="User"
asp-action="Edit" method="post" asp-antiforgery="true">
Like you mention, the asp-antiforgery="true" may be optional, but I like to always add that to make sure that I show my intentions. This works for me every time.
Hope this helps.

Answer 2

Yes, you are correct. You don't have to manually put AntiForgeryToken anymore in ASP.NET Core.
The Form tag helper generates a hidden Request Verification Token to
prevent cross-site request forgery (when used with the
[ValidateAntiForgeryToken] attribute in the HTTP Post action method)
Taken from ASP.NET Core docs
Having that said, are you sure your actions correspond to POST request?
Also specifying the Controller is also a good idea.
<form asp-controller="Users" asp-action="Edit">
P.S: Adding the code for your action methods would help solve the issue faster.