How to preserve current view after api call - asp.net-web-api

Question

Before asp.net core I would invoke a web api from a button by writing some jquery from behind the button click.
I would then handle the data returned from that api call.
Currently I have a view. this view contains a pop up window. In that window I have 3 div sections.
Login
Registration
ForgottenPassword
Focusing on Registration div I allow user to enter email/password/confirm password and let them press a button that calls my web api to validate this process.
So, this is my parent view snippet:
#model InformedWorker.Services.Models.Account
<div id="divLogForm" class="modal-dialog" style="display:none;position:absolute; ">
<div style="background-color: #fefefe;margin: auto;padding: 20px;border: 1px solid #888;">
<div class="modal-header">
<button id="btnClose" type="button" class="close" data-dismiss="modal"><span aria-hidden="true">×</span><span class="sr-only">Close</span></button>
<h4 class="modal-title" id="hdrTitle">LogIn</h4>
</div>
<div class="modal-body">
#{Html.RenderPartial("~/Views/Segments/_Registration.cshtml", Model.Registration);}
#{Html.RenderPartial("~/Views/Segments/_LogIn.cshtml", Model.LogIn);}
#{Html.RenderPartial("~/Views/Segments/_ForgottenRegistration.cshtml", Model.ForgottenloginDetails);}
</div>
</div>
</div>
My registration partial view is this:
#model InformedWorker.Services.Models.Registration
#*
*#
<div class="row" style="display:none" id="divRegistration">
<div class="col-xs-6">
<div class="well">
<div class="form-group">
<label asp-for="EmailAddress" class="control-label"></label>
<input type="text" class="form-control" id="EmailAddress" name="EmailAddress" value="#Model.EmailAddress" required="" title="Please enter you username" placeholder="example#gmail.com">
<span class="help-block"></span>
</div>
<div class="form-group">
<label asp-for="Password" class="control-label">Password</label>
<input type="password" class="form-control" id="Password" name="Password" value="" required="" title="Please enter your password">
<span class="help-block"></span>
</div>
<div class="form-group">
<label asp-for="ConfirmPassword" class="control-label"></label>
<input type="password" class="form-control" id="ConfirmPassword" name="ConfirmPassword" value="" required="" title="Please confirm your password">
</div>
<div id="registerErrorMsg" class="alert alert-error hide">Invalid registration</div>
<a asp-area="" asp-controller="api/Registration" asp-action="Register" class="btn btn-success btn-block">Register</a>
</div>
</div>
<div class="col-xs-6">
<p class="lead">Already Registered?</p>
<p><a onclick="showLogInPage();" class="btn btn-info btn-block">LogIn</a></p>
</div>
</div>
My account Model is this:
public class Account
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long AccountId { get; set; }
public string AccountRef { get; set; }
[Display(Name = "Company Name")]
public string CompanyName { get; set; }
[Display(Name = "Email Address")]
[Required]
[RegularExpression(#"\w+([-+.']\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*", ErrorMessage = "Email address not found")]
[StringLength(60, MinimumLength = 3)]
public string EmailAddress { get; set; }
public string Salt { get; set; }
public string Hash { get; set; }
public bool Disabled { get; set; }
[Display(Name = "Date of Entry")]
public DateTime DOE { get; set; }
public ICollection<Client> Clients { get; set; }
public bool Activated { get; set; }
[NotMapped]
public Registration Registration { get; set; }
[NotMapped]
public LogIn LogIn { get; set; }
[NotMapped]
public ForgottenRegistration ForgottenRegistration { get; set; }
}
My homeController is this:
public IActionResult Index()
{
//var home = new Services.Models.Home();
//home.MyTest = _localizer["ActivationEmailSent"];
//return View(home);
var test = new Services.Models.Account();
test.Registration = new Services.Models.Registration();
test.Registration.EmailAddress = "aaa";
return View(test);
//return View(new Services.Models.Account());
}
My Registration Web api is this:
[Route("api/[controller]")]
public class Registration : Controller
{
// GET api/values/5
[HttpGet("{id}")]
public string Get(Registration Account)//int id)
{
return "Error in reg";
}
}
so my question is that when api is called the whole page page is replaced with 'value'.
how would I parse the data and populate the form fields with the result and preserve the original view?
Should i revert back to jquery and make api call that way?
Have I got this fundamentally wrong?
Thanks