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; }
/// <summary>
/// Initializes a new instance of the <see cref="FlatFileAttribute"/> class.
/// </summary>
/// <param name="position">Each item needs to be ordered so that
/// serialization/deserilization works even if the properties
/// are reordered in the class.</param>
/// <param name="length">Total width in the text file</param>
/// <param name="padding">How to do the padding</param>
public FlatFileAttribute(int position, int length, Padding padding)
{
Position = position;
Length = length;
Padding = padding;
}
}
public enum Padding
{
Left,
Right
}
/// <summary>
/// Serializer making the actual work
/// </summary>
public class Serializer
{
private static IEnumerable<PropertyInfo> 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<T>(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<MyObject>(stream);
}
}
