如何在失去作用域之前修复CA Dispose对象？

Question

CA throw the following message:

CA2000 Dispose objects before losing scope.
In method 'GetMatchingJobsDeferred(BackgroundJobSearchParameters)',
object '<>g__initLocal0' is not disposed along all exception paths.
Call System.IDisposable.Dispose on object '<>g__initLocal0' before 
all references to it are out of scope.

I have disposable type CompositeCollection .

public sealed class CompositeCollection<T> : IEnumerable<T>, IDisposable
{
    private readonly List<IEnumerable<T>> _enumerables = new List<IEnumerable<T>>();
    private readonly List<IDisposable> _disposables = new List<IDisposable>();

    public void Add(IEnumerable<T> enumerable)
    {
        _enumerables.Add(enumerable);
    }

    public void Add(IDeferredResultCollection<T> deferredResultCollection)
    {
        _enumerables.Add(deferredResultCollection);
        _disposables.Add(deferredResultCollection);
    }

    public IEnumerator<T> GetEnumerator()
    {
        return _enumerables.Aggregate((results, enumerable) => results.Concat(enumerable)).GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public void Dispose()
    {
        foreach (var item in _disposables)
        {
            item.Dispose();
        }
    }
}

And that how I used it:

public IDeferredResultCollection<BackgroundJobInfoLight> GetMatchingJobsDeferred(BackgroundJobSearchParameters jobSearchParameters)
{
    var memoryLocatedJobs = GetInMemoryJobs(jobSearchParameters);
    var databaseLocatedJobs = GetInDatabaseJobsDeferred(jobSearchParameters, memoryLocatedJobs);

    return new CompositeCollection<BackgroundJobInfoLight>
    {
        memoryLocatedJobs,
        databaseLocatedJobs
    };
}

I have exception when return statement called. How to fix that?

I add try catch and it doesn't help

 public IDeferredResultCollection<BackgroundJobInfoLight> GetMatchingJobsDeferred(BackgroundJobSearchParameters jobSearchParameters)
    {
        CompositeCollection<BackgroundJobInfoLight> deferredJobs = null;
        DeferredResultCollection<BackgroundJobInfoLight> databaseLocatedJobs = null;
        try
        {
            var memoryLocatedJobs = GetInMemoryJobs(jobSearchParameters);
            databaseLocatedJobs = GetInDatabaseJobsDeferred(jobSearchParameters, memoryLocatedJobs);

            deferredJobs = new CompositeCollection<BackgroundJobInfoLight> { memoryLocatedJobs, databaseLocatedJobs };
            return deferredJobs;
        }
        catch
        {
            if (databaseLocatedJobs != null)
            {
                databaseLocatedJobs.Dispose();
            }

            if (deferredJobs != null)
            {
                deferredJobs.Dispose();
            }

            throw;
        }
    }

Answer 1

When returning the disposable objects, it should be the responsibility of the caller code to Dispose the object. Had the Disposed been called inside the method itself, the disposed object will return to the caller method, ( wont be of any use ).

In that case it is safe to supress the warning.

BUT what if the exception occurred in this method?

If a disposable object is not explicitly disposed before all references to it are out of scope, the object will be disposed at some indeterminate time when the garbage collector runs the finalizer of the object. Because an exceptional event might occur that will prevent the finalizer of the object from running, the object should be explicitly disposed instead. MSDN

So, if you anticipate any exception in the method, you should have this code in try...catch block and in catch block you should call Dispose() checking if the object is not null.

And when you are not returning IDisposable you can use using statement or try...finally and call dispose in finally

Answer 2

Why are you keeping items in to different list variables? It may have something to do with your issue. Keep it DRY Store them in one list and safely cast to what you are looking for.

IDisposable myDispType = myEnumarableType as IDisposable;
If (myDispType != null)
    {//your logic here}