调用的目标已抛出异常 - vb.net

Exception has been thrown by the target of an invocation - vb.net

提问by John Janssen

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

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。

    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: 

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.

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。

"Exception has been thrown by the target of an invocation" error (mscorlib)

“调用的目标已抛出异常”错误 (mscorlib)

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

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

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

任何帮助表示赞赏。如果您需要任何其他信息，请告诉我。

Thanks.

谢谢。

采纳答案by T.S.

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

您没有正确初始化对象。这里...

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

Should be

应该

Private ReadOnly _xml_datatable As New ReportsData_Employee.COATSEndAssignmentDataTable()

Your real issue is

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

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

您需要查看COATSEndAssignmentDataTable. 你NullReferenceException在那里。这两行告诉你确切的位置

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