ASP.NET Core MVC drop down list will not repopulate
Question
I have this drop-down list in my project, and when I use the HttpPost method I have to repopulate it or it's going to throw a null error. I did that, and it worked like normal. However, I'm trying to change a record on my database, and in order to do that, I need the Id to be in the URL. I changed my code in the _Layout to allow the user Id to be automatically entered when they click the tab. But when that happens it throws "ArgumentNullException: Value cannot be null. (Parameter 'items')." Even though I repopulated it. If I don't add the Id, it works, but I change the record on the database. What's going on, why is it not repopulating like before? Also, this is pertaining to the Payee method in the Account controller.
_Layout:
@using Microsoft.AspNetCore.Identity
@using The_Bank_of_Cardinal.Areas.Identity.Data
@inject SignInManager<CardinalUser> SignInManager
@inject UserManager<CardinalUser> UserManager
<style>
#menu ul li {
/*float: left;
border: 1px;
border-style: solid;*/
}
#menu ul li a:hover{
background-color: lightgray;
}
#menu ul ul {
display: none;
height: auto;
padding: 0px;
margin: 0px;
border: 1px;
position: absolute;
border-style: solid;
background-color: white;
z-index : 5000;
}
#menu ul li:hover > ul{
display: block;
}
</style>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>@ViewData["Title"] - The Bank of Cardinal</title>
<link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" />
<link rel="stylesheet" href="~/css/site.css" />
</head>
<body>
<header>
<nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
<div class="container">
@if (SignInManager.IsSignedIn(User))
{
<a class="navbar-brand" asp-area="" asp-controller="Account" asp-action="Index">The Bank of Cardinal</a>
}else
{
<a class="navbar-brand" asp-area="" asp-controller="Home" asp-action="Index">The Bank of Cardinal</a>
}
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target=".navbar-collapse" aria-controls="navbarSupportedContent"
aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div id="menu" class="navbar-collapse collapse d-sm-inline-flex flex-sm-row-reverse">
<partial name="_LoginPartial.cshtml" />
<ul class="navbar-nav flex-grow-1">
@if (SignInManager.IsSignedIn(User))
{
<li class="nav-item"><a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="Index">User Account</a></li>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="Transactions">Transaction History</a></li>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="Deposit" asp-route-id="@UserManager.GetUserAsync(User).Result.Id">Deposit</a></li>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="Transfers">Transfers</a>
<ul>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="Payee" asp-route-id="@UserManager.GetUserAsync(User).Result.Id">User Pay</a>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="BillPay" asp-route-id="@UserManager.GetUserAsync(User).Result.Id">Bill Pay </a>
<li class="nav-item"> <a class="nav-link text-dark" asp-area="" asp-controller="Account" asp-action="AddPayee">Create Payee</a>
</ul>
</li>
}
else
{
<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Index">Home</a>
</li>
<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Transactions">Transactions</a>
</li>
@*<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Test">Test</a>
</li>*@
@*<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Data">User Data</a>
</li>*@
<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Info">User Info</a>
</li>
<li class="nav-item">
<a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
</li>
}
</ul>
</div>
</div>
</nav>
</header>
<div class="container">
<main role="main" class="pb-3">
@RenderBody()
</main>
</div>
<footer class="border-top footer text-muted">
<div class="container">
© 2021 - The_Bank_of_Cardinal - <a asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
</div>
</footer>
<script src="~/lib/jquery/dist/jquery.min.js"></script>
<script src="~/lib/bootstrap/dist/js/bootstrap.bundle.min.js"></script>
<script src="~/js/site.js" asp-append-version="true"></script>
@RenderSection("Scripts", required: false)
</body>
</html>
Account controller:
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using The_Bank_of_Cardinal.Areas.Identity.Data;
using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using The_Bank_of_Cardinal.Models;
namespace The_Bank_of_Cardinal.Controllers
{
[Authorize]
public class AccountController : Controller
{
private readonly TransactionConnection _tc;
private readonly UserManager<CardinalUser> userManager;
private readonly SignInManager<CardinalUser> signInManager;
private readonly DepositConnection _dc;
private readonly PayeeConnection _pc;
public AccountController(TransactionConnection tc, UserManager<CardinalUser> userManager, SignInManager<CardinalUser> signInManager, DepositConnection dc, PayeeConnection pc)
{
_tc = tc;
this.userManager = userManager;
this.signInManager = signInManager;
_dc = dc;
_pc = pc;
}
public IActionResult Index()
{
return View();
}
public IActionResult Transactions()
{
var results = _tc.TransactionHistory.Where(o=> o.UserName == userManager.GetUserAsync(User).Result.UserName).ToList();
return View(results);
}
public IActionResult Test()
{
return View();
}
[HttpGet]
public IActionResult Deposit(string Id)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == Id).FirstOrDefault();
return View(resultss);
}
[HttpPost]
public IActionResult Deposit(DepositModel model, TransactionModel tm)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == model.Id).FirstOrDefault();
double test = model.AccountBalance + userManager.GetUserAsync(User).Result.AccountBalance;
tm.UserName = userManager.GetUserAsync(User).Result.UserName;
string name = tm.UserName;
tm.Description = "personal deposit";
tm.TransactionType = "Deposit";
tm.Amount = "$" + model.AccountBalance.ToString();
tm.Date = DateTime.Now;
model.AccountBalance = test;
_tc.TransactionHistory.Add(tm);
_tc.SaveChanges();
_dc.AspNetUsers.Remove(resultss);
_dc.AspNetUsers.Add(model);
_dc.SaveChanges();
//_dc.AspNetUsers.
return Content("This is your info \n" +
$"Name: {name} \n" +
$"Description: {tm.Description} \n" +
$"type: {tm.TransactionType} \n" +
$"Amount {tm.Amount} \n");
}
public IActionResult Transfers()
{
return View();
}
[HttpGet]
public IActionResult AddPayee() {
return View();
}
[HttpPost]
public IActionResult AddPayee(PayeeModel pm)
{
if (ModelState.IsValid)
{
pm.UserName = userManager.GetUserAsync(User).Result.UserName;
_pc.Payee.Add(pm);
_pc.SaveChanges();
return RedirectToAction("Transfers");
}
return View();
}
[HttpGet]
public IActionResult Payee(string Id)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == Id).FirstOrDefault();
List<PayeeModel> li = new List<PayeeModel>();
li = _pc.Payee.Where(s => s.UserName == userManager.GetUserAsync(User).Result.UserName).ToList();
ViewBag.payeeNames = li;
return View();
}
[HttpPost]
public IActionResult Payee(PayPayee pp, TransactionModel tm, DepositModel model)
{
if (ModelState.IsValid)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == model.Id).FirstOrDefault();
tm.Description = "You Transfered money to the user named " + pp.Name;
tm.Amount = pp.Amount.ToString();
tm.TransactionType = "User Pay";
tm.Date = DateTime.Now;
tm.UserName = userManager.GetUserAsync(User).Result.UserName;
model.AccountBalance = userManager.GetUserAsync(User).Result.AccountBalance - pp.Amount;
_tc.TransactionHistory.Add(tm);
_tc.SaveChanges();
_dc.AspNetUsers.Remove(resultss);
_dc.AspNetUsers.Add(model);
_dc.SaveChanges();
List<PayeeModel> li = new List<PayeeModel>();
li = _pc.Payee.Where(s => s.UserName == userManager.GetUserAsync(User).Result.UserName).ToList();
ViewBag.payeeNames = li;
return View("Transfers");
}
else
{
return View();
}
}
[HttpGet]
public IActionResult BillPay(string Id)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == Id).FirstOrDefault();
return View();
}
[HttpPost]
public IActionResult BillPay(BillPayModel bp, TransactionModel tm, DepositModel model)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == model.Id).FirstOrDefault();
tm.Amount = "$" + bp.Amount.ToString();
tm.UserName = userManager.GetUserAsync(User).Result.UserName;
tm.Description = "you sent " + bp.Company + " a payment \n with the account number " + bp.AccountNumber;
tm.TransactionType = "Bill pay";
tm.Date = DateTime.Now;
model.AccountBalance = userManager.GetUserAsync(User).Result.AccountBalance - bp.Amount;
_tc.TransactionHistory.Add(tm);
_tc.SaveChanges();
_dc.AspNetUsers.Remove(resultss);
_dc.AspNetUsers.Add(model);
_dc.SaveChanges();
return RedirectToAction("Transfers");
}
}
}
PayPayee model:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace The_Bank_of_Cardinal.Models
{
public class PayPayee
{
public string Name { get; set; }
public double Amount { get; set; }
}
}
Payee view:
@model The_Bank_of_Cardinal.Models.PayPayee
@{
ViewData["Title"] = "Payee";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h1>Payee</h1>
<h4>PayeeModel</h4>
<hr />
<div class="row">
<div class="col-md-4">
<form asp-action="Payee">
<div asp-validation-summary="ModelOnly" class="text-danger"></div>
<div class="form-group">
<label asp-for="Name" class="control-label"></label>
<select asp-for="Name" asp-items="@(new SelectList(@ViewBag.payeeNames, "Payee", "Payee"))"></select>
<span asp-validation-for="Name" class="text-danger"></span>
</div>
<div class="form-group">
<label asp-for="Amount" class="control-label"></label>
<input asp-for="Amount" class="form-control" />
<span asp-validation-for="Amount" class="text-danger"></span>
</div>
<div class="form-group">
<input type="submit" value="Create" class="btn btn-primary" />
</div>
</form>
</div>
</div>
<div>
<a asp-action="Index">Back to List</a>
</div>
@section Scripts {
@{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}
2 answers
solution1
0 2021-11-29 07:23:21
You only need to set ViewBag outside if (ModelState.IsValid) :
[HttpPost]
public IActionResult Payee(PayPayee pp, TransactionModel tm, DepositModel model)
{
List<PayeeModel> li = new List<PayeeModel>();
li = _pc.Payee.Where(s => s.UserName == userManager.GetUserAsync(User).Result.UserName).ToList();
ViewBag.payeeNames = li;
if (ModelState.IsValid)
{
var resultss = _dc.AspNetUsers.Where(s => s.Id == model.Id).FirstOrDefault();
tm.Description = "You Transfered money to the user named " + pp.Name;
tm.Amount = pp.Amount.ToString();
tm.TransactionType = "User Pay";
tm.Date = DateTime.Now;
tm.UserName = userManager.GetUserAsync(User).Result.UserName;
model.AccountBalance = userManager.GetUserAsync(User).Result.AccountBalance - pp.Amount;
_tc.TransactionHistory.Add(tm);
_tc.SaveChanges();
_dc.AspNetUsers.Remove(resultss);
_dc.AspNetUsers.Add(model);
_dc.SaveChanges();
return View("Transfers");
}
else
{
return View();
}
}
Without if (ModelState.IsValid) ,sometimes it will get error when you add data to database.
solution2
0 2021-11-30 15:05:29
If your IActionResult with [HttpGet] has a Id as Parameter and you return View or return RedirectToAction then you need to pass the value, to the returned View
Example:
[HttpGet]
public IActionResult Test(string id)
{
//Some code here
return View();
}
[HttpPost]
public IActionResult Test(Bind["Id,FirstName,LastName"] Person model)
{
//some code here
return RedirectToAction(nameof(Test), (new {model.Id}));
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.
Related Question
ASP.NET core 5 MVC Null drop down list option
How to updating number of displayed elements per page with a drop down list in ASP.NET core mvc?
Create drop down list from List ASP.NET MVC
Create drop down list asp.net core
Changing Drop down list ASP.NET CORE
Drop-down list in ASP.NET MVC
Asp.Net MVC with Drop Down List, and SelectListItem Assistance
ASP.NET MVC - Populate a drop down list
How to create a drop down list in ASP.NET MVC3?
Cascading Drop Down List - ASP.NET MVC
Related Tags