wpf 调用的目标已抛出 LINQ 和异常
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/11809530/
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
LINQ and Exception has been thrown by the target of an invocation
提问by Petree
I have WPF .NET FW4 application with linq and SQL CE 4.0. Randomly on customer's notebook I recieving this error:
我有带有 linq 和 SQL CE 4.0 的 WPF .NET FW4 应用程序。随机在客户的笔记本上我收到此错误：
Exception has been thrown by the target of an invocation.
调用的目标已抛出异常。
I already know, that important is Inner exception (with stack trace):
我已经知道，重要的是内部异常（带有堆栈跟踪）：
Object reference not set to an instance of an object. at lambda_method(Closure )
你调用的对象是空的。在 lambda_method(Closure )
Code block:
代码块：
private void LoadCustomersDetail(CustomersView cw)
{
Persons customer = db.Persons.Where(c => c.Person_id == cw.Customer_id).FirstOrDefault();
reg = new RegistrationWindow(db, customer, false);
reg.ShowDialog();
if (reg.DialogResult.Value)
{
if (!onlyDebtors)
LoadCustomers();
else
LoadDebtors();
}
}
Stack trace for original exception:
原始异常的堆栈跟踪：
at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Data.Linq.CommonDataServices.GetKeyFromPredicate(MetaType type, Dictionary`2 keys, Expression mex, Expression vex)
at System.Data.Linq.CommonDataServices.GetKeysFromPredicate(MetaType type, Dictionary`2 keys, Expression expr)
at System.Data.Linq.CommonDataServices.GetKeyValues(MetaType type, LambdaExpression predicate)
at System.Data.Linq.CommonDataServices.GetCachedObject(Expression query)
at System.Data.Linq.CommonDataServices.GetCachedObject(Expression query)
at System.Data.Linq.SqlClient.SqlProvider.GetCachedResult(Expression query)
at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression)
at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
at ProjectName.Core.ViewWindow.LoadCustomersDetail(CustomersView cw)
at ProjectName.Core.ViewWindow.dataGridCustomersList_MouseDoubleClick(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
at System.Windows.Controls.Control.OnMouseDoubleClick(MouseButtonEventArgs e)
at System.Windows.Controls.Control.HandleDoubleClick(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
at System.Windows.UIElement.OnMouseDownThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
回答by H.B.
The exception seems to concern the Where-expression, so either cor cwis null. I would recommend an argument check at the beginning of the method (throw ArgumentNullExceptionif cw == null).
Also make sure the Personscollection contains no null values (if that is even possible).
异常似乎与 -Where表达式有关，因此corcw为空。我建议在方法的开头进行参数检查（throw ArgumentNullExceptionif cw == null）。还要确保Persons集合不包含空值（如果可能的话）。
回答by John Woo
Your error is here cw.Customer_id. your cwis null.
你的错误在这里cw.Customer_id。你的cw是null。
