反序列化时如何从xml生成未指定的数据？

Question

I have xml like this:

<?xml version="1.0" encoding="utf-8"?>
<InputData>
    <MaxCPUBurst>12</MaxCPUBurst>
    <MaxPriority>30</MaxPriority>
    <Processes>
        <Student>
            <CPUBurst>12</CPUBurst>
            <Id>1</Id>
            <Priority>5</Priority>
            <Resources>2</Resources>
            <Group>1</Group>
            <Name>Sidorov Sidor Sidorovich</Name>
        </Student>
        <Student>
            <CPUBurst>11</CPUBurst
            ><Id>2</Id>
            <Priority>8</Priority>
            <Resources>1</Resources>
            <Group>2</Group>
            <Name>Olegov Oleg Olegovich</Name>
        </Student>
        <Student>
            <CPUBurst>14</CPUBurst>
            <Id>7</Id>
            <Resources>1</Resources>
            <Name>Ivanova Anastasiya Igorevna</Name>
        </Student>
    </Processes>
</InputData>

And deserialize it this way:

public class InputData {
    public int MaxCPUBurst { get; set; }
    public int MaxPriority { get; set; }
    public int QuantDuration { get; set; }
    public string PlanningMethod { get; set; }
    public List<Student> Processes;
}

public class Student {
    public int CPUBurst { get; set; }
    public int id { get; set; }
    public int Priority { get; set; }
    public int Group { get; set; }
    public string Name { get; set; }
}

static void Main(string[] args) {
XmlDocument contentxml = new XmlDocument();
    contentxml.Load("INPUT.xml");
    XmlSerializer serializer = new XmlSerializer(typeof(InputData));
    InputData inData;
    using (StringReader reader = new StringReader(contentxml.OuterXml)) {
        inData = (InputData)(serializer.Deserialize(reader));
    }

    Console.WriteLine(inData.Processes.First().Name);
    Console.WriteLine(inData.Processes.Last().Name);
    Console.WriteLine("Press any key");
    Console.ReadLine();
}

As you can see, 3rd student don't have Priority and Group. If this values is not specified, i must set random values instead. What is propper way to do this?

I can check all deserialized data after deserialization but it sounds dumb.

Answer 1

Checking data after deserialization is not dumb.

Since you're not using a relational database or, in other words - a structured persistence provider I would say that a data check after deserialization is required .

The file you are reading from can be altered by other applications from the system or directly by the users so in order to avoid a NullReferenceException later in the flow (and implicitly an application crash) you need to verify/normalize your data.

As a suggestion, you can create two extension methods for that:

public static class DataExtensions
{
    private static readonly Random _random = new Random();

    public static void Normalize(this List<Student> students)
    {
        for(int i=0; i<students.Count; i++)
        {
            students[i].Normalize();
        }
    }

    public static void Normalize(this Student student)
    {
        if(student.Group == 0)
            student.Group = _random.Next();
        if(student.Priority == 0)
            student.Priority = _random.Next();
    }
}

And in your Main method simply use:

inData.Students.Normalize();

Answer 2

I'm still fiddeling around on how to normalize your data before serialization but a quick and dirty way to do it afterwards would be something along those lines:

inData.Processes.Where(x => x.Priority == 0 && x.Group == 0)
                .ToList()
                .ForEach(std => {
                    Random r = new Random();
                    std.Priority = r.Next(1,10);
                    std.Group = r.Next(1,10);
                });

Edit: If you really want to normalize before you serialize, you can do this:

XElement root = XElement.Load(@"path\to\xml");
XmlSerializer serializer = new XmlSerializer(typeof(InputData));
InputData inData;       

root.Elements("Processes")
    .Elements("Student")
    .Where (r => r.Element("Group") == null && r.Element("Priority") == null)
    .ToList()
    .ForEach(x => {
        Random r = new Random();
        x.Add(new XElement("Group", r.Next(1,10)));
        x.Add(new XElement("Priority", r.Next(1,10)));
    });

using (StringReader reader = new StringReader(root.ToString())) 
{
    inData = (InputData)(serializer.Deserialize(reader));
}

Here you are checking if the elements Group and Priority exist. If they do not - you add them in a foreach loop. If we want to be super precise, we'd also need to add the Id and set it to 0 like every one elses Id.

Answer 3

I'm pretty sure that if you set random data in your class constructor it will be overwritten if there is data available in the Xml file and not if there is none.

This way only those items that do not have an Xml counterpart will end up having random data.