问题
When I click submit in order to create an account the following error is displayed. I can't find why it is giving the following error. Also I tried to use breakpoints and debugging but it was useless
No parameterless constructor defined for this object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
AccountController.cs
[HandleError]
public ActionResult CreateNewFixedBankAccount()
{
ViewBag.AccountFromList = new SelectList(
ManageAccount.Instance.GetAccounts(), "accountID", "name");
ViewBag.AccountTypes = new SelectList(ManageAccountType.Instance.GetNonFixedTypes(), "id", "type");
ViewBag.Durations = new SelectList(ManageDuration.Instance.GetAllDurations(), "id", "duration1");
ViewBag.Currencies = new SelectList(ManageCurrency.Instance.getCurrencies(), "id", "symbol");
return View();
}
//
// POST: /Account/CreateNewFixedBankAccount
[HttpPost]
[HandleError]
public ActionResult CreateNewFixedBankAccount(ViewModel.NewAccountViewModel model, string username)
{
return View();
}
___________________________________________________________________________________________
CreateNewFixedBankAccount.cshtml The submit button below gives the error
@model internetBankingApplication.ViewModel.NewFixedAccountViewModel
@{
ViewBag.Title = "CreateNewFixedBankAccount";
}
@using (Html.BeginForm())
{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_Layout.cshtml";
<fieldset>
<legend>Fixed Account Details</legend>
<div class="editor-label">
<br />
<b>@Html.LabelFor(model => model.Name)</b>
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Name)
</div>
<div class="editor-label">
<br />
<b> @Html.LabelFor(model => model.UserName)</b>
</div>
<div class="editor-field">
@Html.EditorFor(model => model.UserName)
</div>
<div class="editor-label">
<br />
<b> @Html.Label("Account From")</b>
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.accountFrom, (SelectList)ViewBag.AccountFromList)
</div>
<div class="editor-label">
<br />
<b> @Html.LabelFor(model => model.AvailableBalance)</b>
</div>
<div class="editor-field">
@Html.EditorFor(model => model.AvailableBalance)
</div>
<div class="editor-label">
<br />
<b>@Html.LabelFor(model => model.currency)</b>
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.currency, (SelectList)ViewBag.Currencies)
</div>
<div class="editor-label">
<br />
<b> @Html.LabelFor(model => model.Description)</b>
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Description)
</div>
<div class="editor-label">
<br />
<b> @Html.LabelFor(model => model.DateOpened)</b>
</div>
<div class="editor-field">
@Html.EditorFor(model => model.DateOpened)
</div>
<div class="editor-label">
<br />
<b> @Html.Label("Account Duration")</b>
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.duration, (SelectList)ViewBag.Durations)
@Html.ActionLink("View Duration Details","DurationDetails","Duration")
</div>
<div class="editor-label">
<br />
<b> @Html.Label("Account Renew")</b>
</div>
<div class="editor-field">
@Html.CheckBoxFor(model => model.renew)
</div>
<p>
<input type="submit" value="CreateNewFixedBankAccount" /></p>
</fieldset>
}
___________________________________________________________________________________________
NewFixedAccountViewModel.cs
This view model will get details that have to do with the account from different tables in the database.
public class NewFixedAccountViewModel
{
private account _Account { get; set; }
private fixedAccount _FixedAccount { get; set; }
private int AccountFrom { get; set; }
public SelectList AccountTypes { get; set; }
public SelectList Durations { get; set; }
public SelectList AccountFromList { get; set; }
public SelectList Currencies { get; set; }
public int ID
{
get
{
return _Account.accountID;
}
}
[Required]
[Display(Name = "Account Name")]
public string Name
{
get
{
return _Account.name;
}
set
{
_Account.name = value;
}
}
[Required]
[Display(Name = "Account From")]
public int accountFrom
{
get
{
return accountFrom;
}
set
{
accountFrom = value;
}
}
public string AccountFromName
{
get
{
string result = string.Empty;
try
{
result = ManageAccount.Instance.GetAccountBYID(accountFrom).name;
}
catch { }
return result;
}
}
[Required]
[Display(Name = "Account Type")]
public int typeID
{
get
{
return _Account.typeID;
}
set
{
_Account.typeID = value;
}
}
public string AccountTypeName
{
get
{
string result = string.Empty;
try
{
result = ManageAccountType.Instance.getTypesByID(_Account.typeID).type;
}
catch { }
return result;
}
}
[Required]
[Display(Name = "Duration")]
public int duration
{
get
{
return _FixedAccount.duration;
}
set
{
_FixedAccount.duration = value;
}
}
public string durationName
{
get
{
string result = string.Empty;
try
{
result = ManageDuration.Instance.GetDurationById(_FixedAccount.duration).duration1;
}
catch { }
return result;
}
}
[Required]
[Display(Name = "Available Balance")]
public decimal AvailableBalance
{
get
{
return _Account.availableBalance;
}
set
{
_Account.availableBalance = value;
}
}
[Required]
[Display(Name = "Currency")]
public int currency
{
get
{
return _Account.currency;
}
set
{
_Account.currency = value;
}
}
public string CurrencyName
{
get
{
string result = string.Empty;
try
{
result = ManageCurrency.Instance.getTypesByID(_Account.currency).name;
}
catch { }
return result;
}
}
[Required]
[Display(Name = "Account Description")]
public string Description
{
get
{
return _Account.description;
}
set
{
_Account.description = value;
}
}
[Required]
[Display(Name = "Account Renew")]
public bool renew
{
get
{
if (_FixedAccount.renew == 0)
{
return false;
}
return true;
}
set
{
if (value == false)
{
_FixedAccount.renew = 0;
}
else
{
_FixedAccount.renew = 1;
}
}
}
[Required]
[Display(Name = "Date Opened")]
public DateTime DateOpened
{
get
{
return _Account.dateOpened;
}
set
{
_Account.dateOpened = value;
}
}
[Required]
[Display(Name = "Username")]
public string UserName
{
get
{
return _Account.username;
}
set
{
_Account.username = value;
}
}
public NewFixedAccountViewModel(string username)
{
AccountTypes = new SelectList(
ManageAccountType.Instance.getTypes(), "id", "type", _Account.typeID);
AccountFromList = new SelectList(
ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);
Currencies = new SelectList(
ManageCurrency.Instance.getCurrencies(), "id", "name", _Account.currency);
Durations = new SelectList(
ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);
}
public NewFixedAccountViewModel(int accountID, string username)
{
_Account = ManageAccount.Instance.GetAccountBYID(accountID);
_FixedAccount = ManageFixedAccount.Instance.GetFixedAccountByID(accountID);
AccountFromList = new SelectList(
ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);
AccountTypes = new SelectList(
ManageAccountType.Instance.getTypes(), "id", "type", _Account.accountType);
Currencies = new SelectList(
ManageCurrency.Instance.getCurrencies(), "id", "name", _Account.currency);
Durations = new SelectList(
ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);
}
回答1:
it's because you don't have parameterless constructor in your ViewModel class. You have 2 constructors there:
- public NewFixedAccountViewModel(string username)
- public NewFixedAccountViewModel(int accountID, string username)
When you submit the form, during model binding, the controller is trying to create a new instance of the model, but it doesn't find parameterless constructor.
So you need to have:
public NewFixedAccountViewModel() {
// Your code here
}
What you can do is maybe use the Username property instead of username parameter, so your code will be:
public NewFixedAccountViewModel()
{
AccountTypes = new SelectList(
ManageAccountType.Instance.getTypes(), "id", "type", _Account.typeID);
AccountFromList = new SelectList(
ManageAccount.Instance.GetUserAccounts(Username), "accountID", "name", accountFrom);
Currencies = new SelectList(
ManageCurrency.Instance.getCurrencies(), "id", "name", _Account.currency);
Durations = new SelectList(
ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);
}
回答2:
I'm not sure if this is quite right, but I think what's happening is you've declared constructors for your model. So it is trying to create a new object based on your model class, but can't because there isn't a constructor that accepts no parameters. I think what you need to do is create a new model in your controller with one of the constructors you have defined and pass it to the view:
NewFixedAccountViewModel model = new NewFixedAccountViewModel(username);
return View(model);
Then it'll bind to the model object you have created with the appropriate constructor and bind the form fields to that instead instead of trying to create a new one.
来源：https://stackoverflow.com/questions/16317757/mvc-asp-net-no-parameterless-constructor-defined-for-this-object