eBayInventoryManagmentSystem.dll中发生了'System.NullReferenceException'类型的异常，但未在用户代码中处理 [英] An exception of type 'System.NullReferenceException' occurred in eBayInventoryManagmentSystem.dll but was not handled in user code
问题描述
[HttpPost]
[ActionName（ExcelUpload）]
public HttpResponseMessage ExcelUpload（）
{
var tbl = new DataTable（Inventory）;
var httpPostedFile = HttpContext.Current.Request.Files [UploadedExcel ];
if（httpPostedFile == null || httpPostedFile.ContentLength< = 0）返回null;
// 1。从OpenXml Excel文件读取（2007格式; * .xlsx）
IExcelDataReader excelReader = ExcelReaderFactory.CreateOpenXmlReader（httpPostedFile.InputStream）;
// 2。 DataSet - 从第一行创建列名
excelReader.IsFirstRowAsColumnNames = true;
DataSet result = excelReader.AsDataSet（）;
// 3。免费资源（IExcelDataReader是IDisposable）
excelReader.Close（）;
DataTable AddFixedPriceItemTable = new DataTable（AddFixedPriceItem）;
DataTable ReviseFixedPriceItem = new DataTable（ReviseFixedPriceItem）;
//根据指定的操作拆分数据表。
IEnumerable< datarow> query1 = from myRow in result.Tables [Sheet1]。AsEnumerable（）
其中myRow.Field< string>（Action）==AddFixedPriceItem
选择myRow;
IEnumerable< datarow> query2 = from myRow in result.Tables [Sheet1]。AsEnumerable（）
其中myRow.Field< string>（Action）==ReviseFixedPriceItem
选择myRow;
//检查行是否返回
if（query1.ToList（）。计数> 0）
{
//将DataRow复制到AddFixedPriceItemTable
AddFixedPriceItemTable = query1.CopyToDataTable< datarow>（）;
//为每次调用生成动态xml。
var AddFiexedPriceItemXml = XMLGenerator.GetXMLAddItemXML（AddFixedPriceItemTable）;
//在Temp文件夹中保存XML文件，如果文件已存在于文件夹中，它将覆盖文件。
File.WriteAllText（HttpContext.Current.Server.MapPath（〜 / TempXML / AddFixedPriceIte m.xml），XMLGenerator.FormateXML（AddFiexedPriceItemXml））;
// Comprese生成的XML文件和Create .gz文件
压缩.CompressXml（AddFiexedPriceItemXml，AddFixedPriceItem）;
//从XML文件中删除所有名称空间并发送到sp以将记录保存到表格中
var AddFiexedPriceItemXmlWithoutNamespace = EbayInventoryManagementSystem.UtilityClasses.XMLGenerator.RemoveAllNamespaces（AddFiexedPriceItemXml）;
//在eBay上的StartListing
HttpResponseMessage AddMessage = eBayBulkListing（ AddFixedPriceItem）;
//将上传的库存保存到库存表中。
EbayDBOpertaions eOperation = new EbayDBOpertaions（）;
eOperation.StoreInventory（AddFiexedPriceItemXmlWithoutNamespace）;
//使用ItemId更新库存表
EbayDBOpertaions.UpdateInventory（LMSAdmin.AddXmlWithOutNamespace）;
}
//检查如果返回行
if（query2.ToList（）。Count> 0）
{
//创建DataTable
ReviseFixedPriceItem = query2.CopyToDataTable< datarow>（）;
//生成用于进行ReviseList调用的XML。
var ReviseFiexedPriceItemXml = XMLGenerator.GetReviseItemXML（ReviseFixedPriceItem）;
if（！string.IsNullOrEmpty（ReviseFiexedPriceItemXml））
{
//从XML文件中删除所有名称空间并发送到sp以将记录保存到表中
var ReviseFiexedPriceItemXmlWithoutNamespace = EbayInventoryManagementSystem.UtilityClasses.XMLGenerator.RemoveAllNamespaces（ReviseFiexedPriceItemXml）;
//在TampXML文件夹中保存生成的XML
File.WriteAllText（HttpContext.Current.Server.MapPath（〜/ TempXML / ReviseFixedPriceItem.xml），XMLGenerator.Form ateXML（ReviseFiexedPriceItemXml））;
//创建生成的XML的zip文件
Compress.CompressXml（ReviseFiexedPriceItemXml，ReviseFixedPriceItem）; < br $> b $ b
//在eBay上修改上市的呼吁
HttpResponseMessage ReviseMsg = eBayBulkListing（ReviseFixedPriceItem）;
if（ReviseMsg.StatusCode == HttpStatusCode.OK）
{
EbayDBOpertaions eOperation = new EbayDBOpertaions（）;
//使用修订列表响应更新库存表。
eOperation.ReviseInventoryTable（ReviseFiexedPriceItemXmlWithoutNamespace）;
}
}
}
返回新的HttpResponseMessage（HttpStatusCode.OK）;
}
[HttpPost]
[ActionName("ExcelUpload")]
public HttpResponseMessage ExcelUpload()
{
var tbl = new DataTable("Inventory");
var httpPostedFile = HttpContext.Current.Request.Files["UploadedExcel"];
if (httpPostedFile == null || httpPostedFile.ContentLength <= 0) return null;
//1. Reading from a OpenXml Excel file (2007 format; *.xlsx)
IExcelDataReader excelReader = ExcelReaderFactory.CreateOpenXmlReader(httpPostedFile.InputStream);
//2. DataSet - Create column names from first row
excelReader.IsFirstRowAsColumnNames = true;
DataSet result = excelReader.AsDataSet();
//3. Free resources (IExcelDataReader is IDisposable)
excelReader.Close();
DataTable AddFixedPriceItemTable = new DataTable("AddFixedPriceItem");
DataTable ReviseFixedPriceItem = new DataTable("ReviseFixedPriceItem");
//Split data table based on action specified.
IEnumerable<datarow> query1 = from myRow in result.Tables["Sheet1"].AsEnumerable()
where myRow.Field<string>("Action") == "AddFixedPriceItem"
select myRow;
IEnumerable<datarow> query2 = from myRow in result.Tables["Sheet1"].AsEnumerable()
where myRow.Field<string>("Action") == "ReviseFixedPriceItem"
select myRow;
//Check if rows are returned
if (query1.ToList().Count > 0)
{
//Copies DataRow to AddFixedPriceItemTable
AddFixedPriceItemTable = query1.CopyToDataTable<datarow>();
//Generate Dynamic xml for each call.
var AddFiexedPriceItemXml = XMLGenerator.GetXMLAddItemXML(AddFixedPriceItemTable);
//Save XML File in Temp Folder and if file already exists in folder it will over ride the file.
File.WriteAllText(HttpContext.Current.Server.MapPath("~/TempXML/AddFixedPriceItem.xml"), XMLGenerator.FormateXML(AddFiexedPriceItemXml));
//Comprese Generated XML file and Create .gz file
Compress.CompressXml(AddFiexedPriceItemXml, "AddFixedPriceItem");
//Remove all the namespaces from XML file and send to sp to save records into table
var AddFiexedPriceItemXmlWithoutNamespace = EbayInventoryManagementSystem.UtilityClasses.XMLGenerator.RemoveAllNamespaces(AddFiexedPriceItemXml);
//StartListing on eBay
HttpResponseMessage AddMessage = eBayBulkListing("AddFixedPriceItem");
//Save uploaded inventory into Inventory Table.
EbayDBOpertaions eOperation = new EbayDBOpertaions();
eOperation.StoreInventory(AddFiexedPriceItemXmlWithoutNamespace);
//Update Inventory table with ItemId
EbayDBOpertaions.UpdateInventory(LMSAdmin.AddXmlWithOutNamespace);
}
//Check if rows are returned
if (query2.ToList().Count > 0)
{
//Create DataTable
ReviseFixedPriceItem = query2.CopyToDataTable<datarow>();
//Generate XML For Making ReviseList Call.
var ReviseFiexedPriceItemXml = XMLGenerator.GetReviseItemXML(ReviseFixedPriceItem);
if (!string.IsNullOrEmpty(ReviseFiexedPriceItemXml))
{
//Remove all the namespaces from XML file and send to sp to save records into table
var ReviseFiexedPriceItemXmlWithoutNamespace = EbayInventoryManagementSystem.UtilityClasses.XMLGenerator.RemoveAllNamespaces(ReviseFiexedPriceItemXml);
//Save generated XML in TampXML folder
File.WriteAllText(HttpContext.Current.Server.MapPath("~/TempXML/ReviseFixedPriceItem.xml"), XMLGenerator.FormateXML(ReviseFiexedPriceItemXml));
//Create zip file of generated XML
Compress.CompressXml(ReviseFiexedPriceItemXml, "ReviseFixedPriceItem");
//Call to revise listing on eBay
HttpResponseMessage ReviseMsg = eBayBulkListing("ReviseFixedPriceItem");
if (ReviseMsg.StatusCode == HttpStatusCode.OK)
{
EbayDBOpertaions eOperation = new EbayDBOpertaions();
//update inventory table with revise listing response.
eOperation.ReviseInventoryTable(ReviseFiexedPriceItemXmlWithoutNamespace);
}
}
}
return new HttpResponseMessage(HttpStatusCode.OK);
}
推荐答案
您没有显示带有对象引用未设置为对象实例消息的异常位置。
不用担心。这是检测和修复的最简单的案例之一。它只是意味着某些引用类型的某个成员/变量通过使用和它的实例（非静态）成员解除引用，这要求此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：要么确保将成员/变量正确初始化为非空引用，要么将其检查为null，如果为null，则执行其他操作。
另请参阅：想要在按钮点击时显示下一条记录。但是如果下一个记录功能的条件对象引用未设置为对象的实例则会出错。
有时候，你不能这样做在调试器下，由一个或另一个原因。一个非常讨厌的情况是，只有在调试信息不可用时构建软件时才会出现问题。在这种情况下，你必须使用更难的方式。首先，你需要确保你永远不会通过静默处理异常来阻止异常的传播（这是开发人员对自己的犯罪，但很常见）。您需要在每个线程的最顶层堆栈帧上捕获绝对所有异常。如果处理类型System.Exception的异常，则可以执行此操作。在处理程序中，您需要记录所有异常信息，尤其是System.Exception.StackTrace：
http://msdn.microsoft.com/en-us/library/system.exception.aspx ，
http://msdn.microsoft.com/en-us/library/ system.exception.stacktrace.aspx 。
堆栈跟踪只是一个字符串，显示从throw语句到处理程序的异常传播的完整路径。通过阅读，您总能找到目的。对于日志记录，使用类System.Diagnostics.EventLog：
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx 。
祝你好运，
-SA
You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.
Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.
Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object".
Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the typeSystem.Exception. In the handler, you need to log all the exception information, especially theSystem.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx,
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx.
The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the classSystem.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx.
Good luck,
—SA
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