调用的目标已抛出异常 - vb.net [英] Exception has been thrown by the target of an invocation - vb.net

问题描述

我有一个问题，我收到错误，调用的目标抛出了异常.我有 new 关键字.我确保 ReportsData_Employee.COATSEndAssignmentDataTable 存在.

I have an issue where I am receiving the error, "Exception has been thrown by the target of an invocation. I have the new keyword in place. I made sure the ReportsData_Employee.COATSEndAssignmentDataTable existed.

    Imports System.Windows.Forms
    Imports Advance.Extensions.Reporting
    Imports CrystalDecisions.Shared
    Imports Advance.Common.Reporting
    Imports System.IO

    Public Class Activity_EndAssignmentTool
        ReadOnly _dt As New DataTable
        Dim _dts As New DataTable
        Dim _bldts As New DataTable
        Dim _xml_file_name_creation As String
    '// This is the line that is causing the error ============
        ReadOnly _xml_datatable As ReportsData_Employee.COATSEndAssignmentDataTable = New ReportsData_Employee.COATSEndAssignmentDataTable()
    '//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   ====================================================================================== 

   System.Reflection.TargetInvocationException was caught
   HResult=-2146232828
   Message=Exception has been thrown by the target of an invocation.
   Source=mscorlib
   StackTrace:
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly,        Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Reflection.Assembly.CreateInstance(String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Reflection.Assembly.CreateInstance(String typeName)
   at Advance.Extensions.Activities.Activity_Form.GetActivityForm(String className) in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Forms\Activity_Form.vb:line 126
   at Advance.Extensions.Activities.Activity_Form.SetActivityClass() in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Forms\Activity_Form.vb:line 60
   InnerException: System.NullReferenceException
   HResult=-2147467261
   Message=Object reference not set to an instance of an object.
   Source=Advance.Extensions.Activities
   StackTrace:
   at Advance.Extensions.Activities.Activity_EndAssignmentTool.InitializeComponent() in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Activity_Forms\Activity_EndAssignmentTool.Designer.vb:line 479
   at Advance.Extensions.Activities.Activity_EndAssignmentTool..ctor() in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Activity_Forms\Activity_EndAssignmentTool.vb:line 12
   InnerException: 

有人可以说出我可能收到此错误的其他一些原因吗?我查看了多个链接，但很多答案不适用于我的情况.

Can someone name some other reasons why I could be getting this error? I have looked at multiple links but a lot of the answers don't apply in my situation.

"异常已经由调用的目标抛出"错误(mscorlib)

仅供参考，我已经尝试将 ReadOnly _xml_datatable 作为 New ReportsData_Employee.COATSEndASsignmentDataTable() 但仍然存在问题.

FYI I have tried ReadOnly _xml_datatable as New ReportsData_Employee.COATSEndASsignmentDataTable() and there was still an issue.

感谢任何帮助.如果您需要任何其他信息，请告诉我.

Any help is appreciated. Let me know if there is any other information you need.

谢谢.

推荐答案

您没有正确初始化对象.这里...

You haven't initialized object properly. Here...

ReadOnly _xml_datatable As ReportsData_Employee.COATSEndAssignmentDataTable = New ReportsData_Employee.COATSEndAssignmentDataTable()

应该是

Private ReadOnly _xml_datatable As New ReportsData_Employee.COATSEndAssignmentDataTable()

你真正的问题是

 InnerException: System.NullReferenceException
 HResult=-2147467261
 Message=Object reference not set to an instance of an object.
 Source=Advance.Extensions.Activities

您需要查看COATSEndAssignmentDataTable 的构造函数.你有 NullReferenceException 在那里.这两行告诉你确切的位置

You need to look into constructor of COATSEndAssignmentDataTable. you have NullReferenceException in there. These two lines tell you exact location

at Advance.Extensions.Activities.Activity_EndAssignmentTool.InitializeComponent()
in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Activity_Forms\Activity_EndAssignmentTool.Designer.vb:line 479

at Advance.Extensions.Activities.Activity_EndAssignmentTool..ctor() 
in C:\Users\JJanssen\Documents\Visual Studio 2010\Projects\Legacy\Advance Extensions\advance.extensions.activities\Activity_Forms\Activity_EndAssignmentTool.vb:line 12

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