为什么更新记录时亚音速和ActiveRecord的抛出异常？ [英] Why is SubSonic and ActiveRecord throwing an exception when updating a record?

问题描述

我在MS SQL Server 2008标准版下表：

I have the following table in MS SQL Server 2008 Standard Edition:

CREATE TABLE [dbo].[NewTestQueue](
    [JobID] [int] IDENTITY(1,1) NOT NULL,
    [ServerName] [varchar](50) NULL,
    [DomainID] [int] NOT NULL,
    [Action] [varchar](50) NULL,
    [Folder] [varchar](150) NULL,
    [Method] [varchar](50) NULL,
    [ActionProfile] [varchar](50) NULL,
    [Title] [varchar](150) NULL,
    [Suffix] [varchar](50) NULL,
    [Host] [varchar](150) NULL,
    [Url] [varchar](250) NULL,
    [Expression] [varchar](50) NULL,
    [MasterTest] [varchar](50) NULL,
    [Completed] [bit] NOT NULL
) ON [PRIMARY]

我使用的是亚音速的ActiveRecord T4模板，并具有下列code：

I'm using the SubSonic ActiveRecord T4 template and have the following code:

var tests = NewTestQueue.Find(d => !d.Completed);
foreach(var test in tests)
{
    // Do some work with test
    // ...

    // Now mark job as completed
    test.Completed = true;

    // System.NullReferenceException thrown here
    test.Update();
}

引发的异常是：

The exception thrown is:

System.NullReferenceException was unhandled
  Message="Object reference not set to an instance of an object."
  Source="SubSonic.Core"
  StackTrace:
       at SubSonic.Extensions.Database.ToUpdateQuery[T](T item, IDataProvider provider)
       at SubSonic.Repository.SubSonicRepository`1.Update(T item, IDataProvider provider)
       at HostMonitor.NewTestQueue.Update(IDataProvider provider) in E:\AppsDev.NET\_UK_Minds\Tollon Components\HostMonitor\Tollon.HostMonitor.TestGenerator\ActiveRecord\ActiveRecord.cs:line 593
       at HostMonitor.NewTestQueue.Update() in E:\AppsDev.NET\_UK_Minds\Tollon Components\HostMonitor\Tollon.HostMonitor.TestGenerator\ActiveRecord\ActiveRecord.cs:line 586
       at Tollon.HostMonitor.TestGenerator.Program.Main(String[] args) in E:\AppsDev.NET\_UK_Minds\Tollon Components\HostMonitor\Tollon.HostMonitor.TestGenerator\Program.cs:line 46
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

这是怎么回事？

Why is this happening?

更新：

我抓住从GitHub上最新的源代码，但现在这打破了由T4模板生成的code。生成的 ActiveRecord.cs 将无法编译，并给出了以下生成错误：

I grabbed the latest source from GitHub but this now breaks the code generated by the T4 template. The generated ActiveRecord.cs won't compile and gives the following build error:

No overload for method 'Load' takes '1' arguments   
[Path snipped]\subsonic-SubSonic-3.0-4748517\SubSonic.Tests\BugReports\Generated\ActiveRecord.cs    
Line: 708

在code其中这个错误发生是这样的：

The code where this error is happening looks like:

    public void Load(IDataReader rdr) {
        Load(rdr, true);
    }
    public void Load(IDataReader rdr, bool closeReader) {
        if (rdr.Read()) {

            try {
                rdr.Load(this); // <<-- Compile error happens here
                SetIsNew(false);
                SetIsLoaded(true);
            } catch {
                SetIsLoaded(false);
                throw;
            }
        }else{
            SetIsLoaded(false);
        }

        if (closeReader)
            rdr.Dispose();
    }

我也尝试无论是原3.0.0.3 ActiveRecord的模板，然后从 SubSonic.Tests 项目中的T4模板。

I did try both the original 3.0.0.3 ActiveRecord template and the T4 templates from the SubSonic.Tests project.

推荐答案

我设法得到了一些时间来重温这一点，并解决的问题。

I managed to get a few moments to revisit this and solve.

这是扔我了，我错过了一个事实，即 rdr.Load（）方法是一个扩展方法（它的已的〜事情凌晨4点），并从已经有它的方法签名改成：

The thing that threw me was that I missed the fact that the rdr.Load() method is an extension method (it was ~4am) and had had its method signature changed from:

public static void Load<T>(this IDataReader rdr, T item)

到

public static void Load<T>(this IDataReader rdr, T item, List<string> ColumnNames)

反正削减长话短说，一旦我意识到这一点，并已经做了查找用法上的方法，所有的电话都只是路过空。然后，我只是修改了 ActiveRecord.tt T4模板来反映这一点。

Anyway to cut a long story short, once I'd realised this and having done a find usages on the method, all of the calls were just passing null. I then just modified the ActiveRecord.tt T4 template to reflect this.

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