TextWriter not writing all files

I've got written a service that has a separate thread running that reads roughly 400 records from a database and serializes them into xml files. It runs fine, there are no errors and it reports all files have been exported correctly, yet only a handful of xml files appear afterwards, and its always a different number each time. I've checked to see if it's a certain record causing problems, but they all read out fine, and seem to write fin, but don't...

After playing around and putting a delay in of 250ms between each write they are all exported properly, so I assume it must have something to do with writing so many files in such a quick succession, but I have no idea why, I would have thought it would report some kind of error if they didn't write properly, yet there's nothing.

Here is the code for anyone who wants to try it:

static void Main(string[] args)
{
    ExportTestData();
}

public static void ExportTestData()
{
    List<TestObject> testObjs = GetData();

    foreach (TestObject obj in testObjs)
    {
        ExportObj(obj);
        //Thread.Sleep(10);
    }
}

public static List<TestObject> GetData()
{
    List<TestObject> result = new List<TestObject>();

    for (int i = 0; i < 500; i++)
    {
        result.Add(new TestObject()
        {
            Date = DateTime.Now.AddDays(-1),
            AnotherDate = DateTime.Now.AddDays(-2),
            AnotherAnotherDate = DateTime.Now,
            DoubleOne = 1.0,
            DoubleTwo = 2.0,
            DoubleThree = 3.0,
            Number = 345,
            SomeCode = "blah",
            SomeId = "wobble wobble"
        });
    }

    return result;
}

public static void ExportObj(TestObject obj)
{
    try
    {
        string path = Path.Combine(@"C:\temp\exports", String.Format("{0}-{1}{2}", DateTime.Now.ToString("yyyyMMdd"), String.Format("{0:HHmmssfff}", DateTime.Now), ".xml"));
        SerializeTo(obj, path);
    }
    catch (Exception ex)
    {

    }
}

public static bool SerializeTo<T>(T obj, string path)
{
    XmlSerializer xs = new XmlSerializer(obj.GetType());
    using (TextWriter writer = new StreamWriter(path, false))
    {
        xs.Serialize(writer, obj);
    }
    return true;
}

Try commenting\uncommenting the Thread.Sleep(10) to see the problem

Does anybody have any idea why it does this? And can suggest how I can avoid this problem?

Than开发者_StackOverflow社区ks

EDIT: Solved. The time based filename wasn't unique enough and was overwriting previously written files. Should've spotted it earlier, thanks for your help

Perhaps try putting the writer in a using block for immediate disposal? Something like

XmlSerializer xs = new XmlSerializer(obj.GetType());
using(TextWriter writer = new StreamWriter(path, false)) 
{
    xs.Serialize(writer, obj);
}

Ok I've found the problem, I was using a time based filename that I thought would be unique enough for each file, turns out in a loop that tight they're coming out with the same filenames and are over-writing each other.

If I change it to use actually unique filenames it works! Thanks for your help

Dispose the writer

public static bool SerializeTo<T>(T obj, string path)
{
    XmlSerializer xs = new XmlSerializer(obj.GetType());
    using(TextWriter writer = new StreamWriter(path, false)) {
        xs.Serialize(writer, obj);
        writer.Close();
    }
    return true;
}

If you're not getting any exceptions, then the using statements proposed by other answers won't help - although you should change to use them anyway. At that point, you don't need the close call any more:

XmlSerializer xs = new XmlSerializer(obj.GetType());
using(TextWriter writer = new StreamWriter(path, false))
{
    xs.Serialize(writer, obj);
}

I don't think the problem lies in this code, however. I suspect it's something like the "capturing a loop variable in a lambda expression" problem which crops up so often. If you can come up with a short but complete program which demonstrates the problem, it will be a lot easier to diagnose.

I suggest you create a simple console application which tries to create (say) 5000 files serializing some simple object. See if you can get that to fail in the same way.

Multi-threading may cause that problem. The 250ms delay is an evidence of that.

Do you have multiple threads doing that?