Custom serialization of an object in .NET

Question

I have a requirement to serialize a list of objects to a flat file. The calls will be something like:

class MyObject
{
    public int x;
    public int y;
           


        

Answer 1

Here is a solution that uses plain old reflection and a custom attribute. It will only serialize/deserialize one item per file, but you could easily add support for multiple items per file.

// Attribute making it possible
public class FlatFileAttribute : Attribute
{
    public int Position { get; set; }
    public int Length { get; set; }
    public Padding Padding { get; set; }

    /// 

    /// Initializes a new instance of the  class.
    /// 
    /// Each item needs to be ordered so that 
    /// serialization/deserilization works even if the properties 
    /// are reordered in the class.
    /// Total width in the text file
    /// How to do the padding
    public FlatFileAttribute(int position, int length, Padding padding)
    {
        Position = position;
        Length = length;
        Padding = padding;
    }
}

public enum Padding
{
    Left,
    Right
}


/// 

/// Serializer making the actual work
/// 
public class Serializer
{
    private static IEnumerable GetProperties(Type type)
    {
        var attributeType = typeof(FlatFileAttribute);

        return type
            .GetProperties()
            .Where(prop => prop.GetCustomAttributes(attributeType, false).Any())
            .OrderBy(
                prop =>
                ((FlatFileAttribute)prop.GetCustomAttributes(attributeType, false).First()).
                    Position);
    }
    public static void Serialize(object obj, Stream target)
    {
        var properties = GetProperties(obj.GetType());

        using (var writer = new StreamWriter(target))
        {
            var attributeType = typeof(FlatFileAttribute);
            foreach (var propertyInfo in properties)
            {
                var value = propertyInfo.GetValue(obj, null).ToString();
                var attr = (FlatFileAttribute)propertyInfo.GetCustomAttributes(attributeType, false).First();
                value = attr.Padding == Padding.Left ? value.PadLeft(attr.Length) : value.PadRight(attr.Length);
                writer.Write(value);
            }
            writer.WriteLine();
        }
    }

    public static T Deserialize(Stream source) where T : class, new()
    {
        var properties = GetProperties(typeof(T));
        var obj = new T();
        using (var reader = new StreamReader(source))
        {
            var attributeType = typeof(FlatFileAttribute);
            foreach (var propertyInfo in properties)
            {
                var attr = (FlatFileAttribute)propertyInfo.GetCustomAttributes(attributeType, false).First();
                var buffer = new char[attr.Length];
                reader.Read(buffer, 0, buffer.Length);
                var value = new string(buffer).Trim();

                if (propertyInfo.PropertyType != typeof(string))
                    propertyInfo.SetValue(obj, Convert.ChangeType(value, propertyInfo.PropertyType), null);
                else
                    propertyInfo.SetValue(obj, value.Trim(), null);
            }
        }
        return obj;
    }

}

And a small demo:

// Sample class using the attributes
public class MyObject
{
    // First field in the file, total width of 5 chars, pad left
    [FlatFile(1, 5, Padding.Left)]
    public int Age { get; set; }

    // Second field in the file, total width of 40 chars, pad right
    [FlatFile(2, 40, Padding.Right)]
    public string Name { get; set; }
}

private static void Main(string[] args)
{
    // Serialize an object
    using (var stream = File.OpenWrite("C:\\temp.dat"))
    {
        var obj = new MyObject { Age = 10, Name = "Sven" };
        Serializer.Serialize(obj, stream);
    }

    // Deserialzie it from the file
    MyObject readFromFile = null;
    using (var stream = File.OpenRead("C:\\temp.dat"))
    {
        readFromFile = Serializer.Deserialize(stream);
    }

}