ASP.NET MVC Model property is null when POST method is called

Question

In a controller action, I have the following call, where userId is a known non-null value:

return View("ChangePassword", new ChangePasswordBindingModel(userId));

Here is the definition of ChangePasswordBindingModel:

public class ChangePasswordBindingModel
{
    private string currentUserId;
    [Required]
    [DataType(DataType.Password)]
    //[Display(Name = "Current password")]
    public string OldPassword { get; set; }

    [Required]
    //[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    [Display(Name = "New password")]
    public string NewPassword { get; set; }

    [Required]
    [DataType(DataType.Password)]
    //[Display(Name = "Confirm new password")]
    [Compare("NewPassword", ErrorMessage = "The new password and confirmation password do not match.")]
    public string ConfirmPassword { get; set; }

    public ChangePasswordBindingModel()
    {

    }
    public ChangePasswordBindingModel(string userId)
    {
        this.currentUserId = userId;
    }

    public string GetUserId()
    {
        return this.currentUserId;
    }
}

Here is the view that is bound to this Model for ChangePassword:

@model IdentityDevelopment.Models.ChangePasswordBindingModel
@{ ViewBag.Title = "ChangePassword";
}

@Html.ValidationSummary(false)
<h2>Change Password</h2>


@using (Html.BeginForm("ChangePassword","Account", FormMethod.Post))
{
   @Html.AntiForgeryToken();
    <input type="hidden" name="returnUrl" value="@ViewBag.returnUrl" />

    <div class="form-group">
        <label>Current Password</label>
        @Html.PasswordFor(x => x.OldPassword, new { @class = "form-control" })
    </div>

    <div class="form-group">
        <label>New Password</label>
        @Html.PasswordFor(x => x.NewPassword, new { @class = "form-control" })
    </div>


    <div class="form-group">
        <label>Re-enter New Password</label>
        @Html.PasswordFor(x => x.ConfirmPassword, new { @class = "form-control" })
    </div>

    <!-- <button class="btn btn-primary" type="submit">Save</button> -->
    <input class="btn btn-primary" type="submit" value="Save" />
}

And lastly, here is the Post method for clicking Save on the above form:

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> ChangePassword(ChangePasswordBindingModel loginChange)
{
    if (ModelState.IsValid)
    {
        IdentityResult result = null;
        try
        {
            string userid = loginChange.GetUserId();
            result = await UserManager.ChangePasswordAsync(userid, loginChange.OldPassword, loginChange.NewPassword);

        }
        catch (Exception ex)
        {

        }
        if (result != null && result.Succeeded)
        {
            return RedirectToAction("Index");
        }
        else
        {
            if(result != null)
            {
                AddErrorsFromResult(result);
            }

        }
    }

    return View(loginChange);
}

The problem is that the userid does not get set to a non-null value, as I thought GetUserId() would do. Why does the currentUserId property of the Model that was sent to the post method not contain the value? I confirmed this is so by stepping into the call to GetUserId() during debugging.

Answer 1

currentUserId isn't submitted to the post action method because of two reasons:

1. currentUserId isn't a public property.
2. It's not present inside using (Html.BeginForm block in <input>, <textarea> or <select> tags.

Remove currentUserId and create a new public property named CurrentUserId in your model. You also don't need the GetUserId() method. Your model should look like below

public class ChangePasswordBindingModel
{
    [Required]
    [DataType(DataType.Password)]
    //[Display(Name = "Current password")]
    public string OldPassword { get; set; }

    [Required]
    //[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    [Display(Name = "New password")]
    public string NewPassword { get; set; }

    [Required]
    [DataType(DataType.Password)]
    //[Display(Name = "Confirm new password")]
    [Compare("NewPassword", ErrorMessage = "The new password and confirmation password do not match.")]
    public string ConfirmPassword { get; set; }

    public string CurrentUserId { get; set; }

    public ChangePasswordBindingModel()
    {

    }
    public ChangePasswordBindingModel(string userId)
    {
        this.CurrentUserId = userId;
    }

}

and use a HiddenField to include CurrentUserId in your view

@using (Html.BeginForm("ChangePassword","Account", FormMethod.Post))
{
   @Html.AntiForgeryToken();
    @Html.HiddenFor(x => x.CurrentUserId)
    <input type="hidden" name="returnUrl" value="@ViewBag.returnUrl" />

    <div class="form-group">
        <label>Current Password</label>
        @Html.PasswordFor(x => x.OldPassword, new { @class = "form-control" })
    </div>

    <div class="form-group">
        <label>New Password</label>
        @Html.PasswordFor(x => x.NewPassword, new { @class = "form-control" })
    </div>


    <div class="form-group">
        <label>Re-enter New Password</label>
        @Html.PasswordFor(x => x.ConfirmPassword, new { @class = "form-control" })
    </div>

    <!-- <button class="btn btn-primary" type="submit">Save</button> -->
    <input class="btn btn-primary" type="submit" value="Save" />
}

In your post action method, you can get the value of CurrentUserId property as below

result = await UserManager.ChangePasswordAsync(loginChange.CurrentUserId, loginChange.OldPassword, loginChange.NewPassword);