Question

我正在创建一个MVC4应用程序，当我尝试将一个表单从我的视图恢复到我的控制器时，我遇到了一些麻烦。

我在主题上阅读了几篇SO帖子，但不幸的是，我没有设法找到哪个对象没有无参数构造函数。我的所有模型类都有一个无参数构造函数。在调试中，错误堆栈只在Internet Explorer中，但在visual studio中没有任何反应。

这是错误堆栈：

异常详细信息：System.MissingMethodException：没有为此对象定义无参数构造函数。

来源错误：

在执行当前Web请求期间生成了未处理的异常。可以使用下面的异常堆栈跟踪来识别有关异常的起源和位置的信息。

堆栈追踪：

[MissingMethodException: No parameterless constructor defined for this object.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +117
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +247
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +106
   System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) +243
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +151
   System.Web.Mvc.DefaultModelBinder.UpdateCollection(ControllerContext controllerContext, ModelBindingContext bindingContext, Type elementType) +545
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +609
   System.Web.Mvc.DefaultModelBinder.GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder) +33
   System.Web.Mvc.DefaultModelBinder.BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor) +497
   System.Web.Mvc.DefaultModelBinder.BindProperties(ControllerContext controllerContext, ModelBindingContext bindingContext) +283
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +677
   System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +489
   System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +153
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState) +883059
   System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +137
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +167
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag) +27
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__17(AsyncCallback asyncCallback, Object asyncState) +50
   System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +137
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +167
   System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback, Object state) +869289
   System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +137
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +167
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) +27
   System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +391
   System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__3(AsyncCallback asyncCallback, Object asyncState) +827094
   System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +137
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +167
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) +27
   System.Web.Mvc.<>c__DisplayClass6.<BeginProcessRequest>b__2() +283
   System.Web.Mvc.<>c__DisplayClassb`1.<ProcessInApplicationTrust>b__a() +19
   System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Func`1 func) +161
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +405
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +375

我的模型类：

 public class Form
    {
        public Form()
        {
            this.Rows = new List<Row>();
        }

        public List<Row> Rows { get; set; }
    }

    public class Row
    {
        protected Row()
        {
            this.Label = string.Empty;
            this.Type = string.Empty;
        }

        public string Label { get; set; }

        public string Type { get; set; }
    }

    public class SimpleRow : Row
    {
        public SimpleRow()
        {
            this.Value = string.Empty;
        }

        public string Value { get; set; }
    }


    public class DropDownRow : Row
    {
        public DropDownRow()
        {
            this.Content = new List<ContentDropDown>();
        }

        public List<ContentDropDown> Content { get; set; }
    }


    public class ContentDropDown
    {
        public ContentDropDown()
        {
            this.Title = string.Empty;
            this.Selected = false;
        }

        public string Title { get; set; }

        public bool Selected { get; set; }
    }

Answer 1

如果您的基础类被定义为接受参数，也会发生这种情况。由于MVC无法传递正确的值，因此失败。尝试声明一个无参数类。这解决了按钮点击回发期间的问题。

例如：

public class Employee
{

   public int EmployeeID {get;set;}
   public string EmployeeName {get;set;}
   public int CostCenter {get;set;}
   public DateTime StartDate {get;set;}

   public Employee(int employeeID)
   {
       //Initialize values
   }

   //Also include a parameter-less construct like below
   public Employee()
   {
   }


}

Answer 2

Row班级的默认构造函数为protected。尝试将其更改为public。

System.MissingMethodException：没有为此对象定义的无参数构造函数。 MVC4

2 个答案: