How to get user timezone offset and send it to the server in ASP.net application

Question

I am confused on how capture/send user's timezone/offset when user does a successful sign in. On internet I found "getTimezoneOffset" to get the work done. But I don't know how to send a data which is calculated implicitly in javascript and not filled explicitly by user in the login in form. Do I need some hidden filed or something which triggers the javascript and then captures its value which I can send back to the server. Please guide me. Below is what I have till now

CSHTML File:

@model LoginMV
@using SIM_Obj.ModelViews;

@{ 
    ViewBag.Title = "Tenant Login";
}

@using (Html.BeginForm("LoginSubmit", "Security", FormMethod.Post, new { id = "simLogin" }))
{
    @Html.AntiForgeryToken()

    <div class="form-horizontal-width-inherit">
        @Html.HiddenFor(model => model.ReturnUrl)

        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.ValidationMessageFor(model => model.Username, "", new { @class = "text-danger" })
            @Html.LabelFor(model => model.Username, htmlAttributes: new { @class = "control-label ignoreSpacing col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Username, new { @class = "form-control" } )
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Password, htmlAttributes: new { @class = "control-label ignoreSpacing col-md-2" })
            <div class="col-md-10">
                @Html.PasswordFor(model => model.Password, new { @class = "form-control" } )
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Login" class="btn btn-default" />
            </div>
        </div>
    </div>
}

ViewModel:

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult LoginSubmit(LoginMV userData)
{
    if (userData != null && !string.IsNullOrEmpty(userData.Username) && !string.IsNullOrEmpty(userData.Password))
    {
        UserMV authenticatedUser = SecurityHelper.AuthenticateTenantUser(userData.Username, userData.Password);

        if (authenticatedUser == null)
        { ModelState.AddModelError("Username", "Incorrect"); }
        else
        {
            SimUtils.CurrentTenantId = authenticatedUser.Id;
            SimUtils.CurrentAccountId = authenticatedUser.AccountId;
        }
    }

    return View("Login", userData);
}

Answer 1

The easiest way to the pass the user's current date/time up to your server would be to use hidden fields on a razor form to send extra data up to the controller.

Do something like this.

In your view, add:

@Html.Hidden('UserLogInDate', null, new {id = "hidUserLoginDate"})

That will create the hidden field on your view giving it the ID as specified.

Then you may (should) have a separate JavaScript file for the login view. In there you can populate the hidden field with the client date/time as the user opens the view.

You then need to include that field in you model, such as:

public datetime UserLogInDate {get; set;}

With that you will be able to process the date/time and get the timezone in your controller.