FileHelpers 库可以编写包含可为空字段的类并读取它们吗？

发布于 2024-10-18 04:21:30 字数 1930 浏览 5 评论 0原文

我正在使用 FileHelpers 库的 2.0 版本，该库被记录为能够处理 .NET 2.0 Nullable 类型。

我正在使用文档中示例中给出的代码：

[DelimitedRecord("|")]   
public class Orders   
{   
    public int OrderID;   

    public DateTime? OrderDate;   

    [FieldConverter(ConverterKind.Date, "ddMMyyyy")]     
    public DateTime? RequiredDate;   

    public int? ShipVia;   
}

使用 FileHelperEngine，我可以成功读取一个没有 OrderDate、RequiredDate 或 ShipVia 字段值的文件。该文件如下所示：

1|||

但是，我无法将生成的 Orders[] 写入文件 - 库抛出 NullReferenceException，堆栈跟踪如下：

at FileHelpers.ConvertHelpers.CultureConverter.FieldToString(Object from) 在 FileHelpers.FieldBase.BaseFieldString(Object fieldValue) 在 FileHelpers.DelimitedField.CreateFieldString（StringBuilder sb，对象 fieldValue）在 FileHelpers.FieldBase.AssignToString(StringBuilder sb，对象 fieldValue) 在 FileHelpers.RecordInfo.RecordToString（对象记录）在 FileHelpers.FileHelperEngine1.WriteStream(TextWriter writer, IEnumerable1 条记录，Int32 maxRecords) 在 FileHelpers.FileHelperEngine1.WriteFile(String fileName, IEnumerable1 条记录, Int32 maxRecords) 在 FileHelpers.FileHelperEngine1.WriteFile(String fileName, IEnumerable1 条记录) 在C:\dev\src\TestingFileHelpers\TestingFileHelpers\Program.cs中的TestingFileHelpers.Program.Main(String[] args)：第19行在 System.AppDomain._nExecuteAssembly（RuntimeAssembly 程序集，String[] args）在 System.AppDomain.ExecuteAssembly（字符串 assemblyFile，证据 assemblySecurity，字符串 [] args）在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() 在 System.Threading.ThreadHelper.ThreadStart_Context（对象状态）在System.Threading.ExecutionContext.Run（ExecutionContextexecutionContext，ContextCallback回调，对象状态，布尔ignoreSyncCtx）在 System.Threading.ExecutionContext.Run（ExecutionContextexecutionContext，ContextCallback 回调，对象状态）在 System.Threading.ThreadHelper.ThreadStart()

我确信我一定在这里遗漏了一些东西，但我不知道它是什么。非常感谢任何帮助。

原文

I'm using version 2.0 of the FileHelpers library which is documented as being able to handle .NET 2.0 Nullable types.

I'm using the code given in the example from the documentation:

[DelimitedRecord("|")]   
public class Orders   
{   
    public int OrderID;   

    public DateTime? OrderDate;   

    [FieldConverter(ConverterKind.Date, "ddMMyyyy")]     
    public DateTime? RequiredDate;   

    public int? ShipVia;   
}

With a FileHelperEngine I can successfully read in a file which has no value for the OrderDate, RequiredDate or ShipVia fields. The file looks like:

1|||

However, I cannot then write out the resulting Orders[] to file - the library throws a NullReferenceException, stack trace below:

at FileHelpers.ConvertHelpers.CultureConverter.FieldToString(Object from)
at FileHelpers.FieldBase.BaseFieldString(Object fieldValue)
at FileHelpers.DelimitedField.CreateFieldString(StringBuilder sb, Object fieldValue)
at FileHelpers.FieldBase.AssignToString(StringBuilder sb, Object fieldValue)
at FileHelpers.RecordInfo.RecordToString(Object record)
at FileHelpers.FileHelperEngine1.WriteStream(TextWriter writer, IEnumerable1 records, Int32 maxRecords)
at FileHelpers.FileHelperEngine1.WriteFile(String fileName, IEnumerable1 records, Int32 maxRecords)
at FileHelpers.FileHelperEngine1.WriteFile(String fileName, IEnumerable1 records)
at TestingFileHelpers.Program.Main(String[] args) in C:\dev\src\TestingFileHelpers\TestingFileHelpers\Program.cs:line 19
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()