asp.net-mvc System.InvalidCastException：无法将“System.Int32”类型的对象转换为“System.String”类型
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19204979/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
System.InvalidCastException: Unable to cast object of type 'System.Int32' to type 'System.String'
提问by kayze
I've been stuck trying to debug this issue. I believe the error Is occurring when I am trying to populate a drop down list.
我一直在尝试调试这个问题。我相信当我尝试填充下拉列表时会发生错误。
IEnumerable<Customer> values = db.Customers.SqlQuery("SELECT * FROM Customer").ToList().Cast<Customer>();
IEnumerable<SelectListItem> items =
from value in values
select new SelectListItem
{
Text = value.CustomerID.ToString(),
Value = value.CustomerID.ToString(),
};
ViewBag.Accounts = items;
Stack Trace
堆栈跟踪
[InvalidCastException: Unable to cast object of type 'System.Int32' to type 'System.String'.]
[InvalidCastException：无法将“System.Int32”类型的对象转换为“System.String”类型。]
System.ComponentModel.DataAnnotations.StringLengthAttribute.IsValid(Object value) +46
System.ComponentModel.DataAnnotations.ValidationAttribute.IsValid(Object value, ValidationContext validationContext) +115
System.ComponentModel.DataAnnotations.ValidationAttribute.GetValidationResult(Object value, ValidationContext validationContext) +29
System.Web.Mvc.<Validate>d__15.MoveNext() +161
System.Web.Mvc.<Validate>d__1.MoveNext() +311
System.Web.Mvc.DefaultModelBinder.OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext) +136
System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model) +66
System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +1314
System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +416
System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +317
System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +117
System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState) +446
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +130
System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeAction(ControllerContext controllerContext, String actionName, AsyncCallback callback, Object state) +302
System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__17(AsyncCallback asyncCallback, Object asyncState) +30
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +130
System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback, Object state) +382
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +130
System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +317
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +15
System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__2(AsyncCallback asyncCallback, Object asyncState) +71
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +130
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +249
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +50
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +301
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155
回答by Aron
Judging from the exception message your Customer class looks something like this...
从异常消息来看，您的 Customer 类看起来像这样......
public class Customer
{
[StringLength(4)]
public int CustomerID { get; set;}
}
Notice that you can't use StringLengthon an intproperty.
请注意，您不能StringLength在int属性上使用。
Get rid of the StringLengthand the validation exceptions should go away.
摆脱StringLength并且验证异常应该消失。
