ASP.Net Core Razor Pages: How to return the complex model on post? - asp.net-core

Question

I created a new ASP.Net Core 2 (Razor Pages) Project
My model is:
public class FormularioGenerico
{
public FormularioGenerico()
{
}
public string IP { get; set; }
public List<string> items { get; set; } = new List<string>();
}
On the page I put
on the page.cshtml.cs
public class EditarModel : PageModel
{
[BindProperty]
public FormularioGenerico ff { get; set; }
[BindProperty]
public string Message { get; set; }
public void OnGet()
{
this.ff = new FormularioGenerico();
ff.IP = "C# FORM";
ff.items.Add("OK1");
ff.items.Add("OK2");
ff.items.Add("OK3");
}
public async Task<IActionResult> OnPostAsync()
{
if (!ModelState.IsValid)
{
return Page();
}
var m = ModelState.IsValid; // true
Debug.WriteLine(this.ff.IP); // is Always returning null
Debug.WriteLine(this.ff.items.Count); // is Always returning null
}
}
on the page.cshtml:
#model Formulario.Pages.EditarModel
...
<h1>#Model.ff.IP</h1>
#foreach (var i in Model.ff.items)
{
<div>#i</div>
}
<button type="submit">Enviar</button>
The items are correctly output. But the complete object does not go to the OnPost.
The problem is: The model is not coming fully populated on the OnPost.
How to receive the full object that was created on the OnGet, plus the changes made by the user on the form, on the post to OnPostAsync() ?

Answer 1

The BindProperty attribute is used to inform ASP.NET Core that the values that the form submitted should be mapped to the specified object. In your case you set the values for the ff property but you do not have the equivalent input values so that ASP.NET Core will get these values in order to store them back to the ff property.
In order to make it work you will have to replace your razor code with the following code:
<form method="post">
<h1>#Model.ff.IP</h1>
<input asp-for="#Model.ff.IP" type="hidden" /> #* create a hidden input for the IP *#
#for (int i = 0; i < Model.ff.items.Count(); i++)
{
<input asp-for="#Model.ff.items[i]" type="hidden" /> #* create a hidden input for each item in your list *#
<div>#Model.ff.items[i]</div>
}
<button type="submit">Enviar</button>
</form>
Very important. To make this work you can not use the foreach loop because ASP.NET core will not be able to find the values. You will have to use a for loop.
The inputs that I added are hidden because I guess you do not want them to be visible but you can remore the type="hidden" so that you will be able to see them. Every change that you make to these inputs will be submitted to the OnPostAsync method.