Debugger not showing dictionary during binary serialization

Question

When I am in the debugger and I step into the DataContext serialization constructor the _regionsDictionary has a count of zero. However, in main program Deserialize method (Program.Deserialize()) the DataContext has the proper items.  Why is the debugger
showing no objects in the DataContext(Serialization info, StreamingContext context) constructor?
class Program
static void Main(string[] args)
Serialize();
Deserialize();
static void Serialize()
var appContext = new DataContext();
List<IShapeRegion> rectRegions = new List<IShapeRegion>();
rectRegions.Add(new RectangleRegion(5, 3));
rectRegions.Add(new RectangleRegion(2, 2));
appContext.Insert("RectangularRegions", rectRegions);
FileStream fs = new FileStream("DataFile.dat", FileMode.Create);
BinaryFormatter formatter = new BinaryFormatter();
try
formatter.Serialize(fs, appContext);
catch (SerializationException e)
Console.WriteLine("Failed to serialize. Reason: " + e.Message);
throw;
finally
fs.Close();
static void Deserialize()
DataContext context = null;
FileStream fs = new FileStream("DataFile.dat", FileMode.Open);
try
BinaryFormatter formatter = new BinaryFormatter();
context = (DataContext)formatter.Deserialize(fs);
catch (SerializationException e)
Console.WriteLine("Failed to deserialize. Reason: " + e.Message);
throw;
finally
fs.Close();
var rectangularRegions = context.GetRegionByName("RectangularRegions");
foreach (var region in rectangularRegions)
Console.WriteLine(region.ToString());
[Serializable]
public class DataContext : ISerializable
private Dictionary<string, List<IShapeRegion>> _regionsDictionary;
public DataContext()
_regionsDictionary = new Dictionary<string, List<IShapeRegion>>();
public void Insert(string regionName, List<IShapeRegion> regions)
_regionsDictionary.Add(regionName, regions);
public List<IShapeRegion> GetRegionByName(string regionName)
var regions = _regionsDictionary.FirstOrDefault(x => x.Key == regionName).Value;
return regions;
public void GetObjectData(SerializationInfo info, StreamingContext context)
info.AddValue("RegionsDictionary", _regionsDictionary);
protected DataContext(SerializationInfo info, StreamingContext context)
SerializationInfoEnumerator e = info.GetEnumerator();
while (e.MoveNext())
switch (e.Name)
case "RegionsDictionary":
_regionsDictionary = (Dictionary<string, List<IShapeRegion>>)e.Value;
break;
public interface IShapeRegion
double Area();
[Serializable]
public class RectangleRegion : IShapeRegion, ISerializable
private double _length_in;
private double _width_in;
public RectangleRegion(double length_in, double width_in)
_length_in = length_in;
_width_in = width_in;
public double Area()
return _length_in * _width_in;
public void GetObjectData(SerializationInfo info, StreamingContext context)
info.AddValue("Length", _length_in);
info.AddValue("Width", _width_in);
protected RectangleRegion(SerializationInfo info, StreamingContext context)
SerializationInfoEnumerator e = info.GetEnumerator();
while (e.MoveNext())
switch (e.Name)
case "Length":
_length_in = Convert.ToDouble(e.Value);
break;
case "Width":
_width_in = Convert.ToDouble(e.Value);
break;
public override string ToString()
return String.Format("Rectangle: Length = {0}, Width = {1}", _length_in, _width_in);

Answer 1

According to one article, the deserialization operation is a complex process which is not always well documented.
Try this workaround:
case
"RegionsDictionary":
_regionsDictionary = (Dictionary<string,
List<IShapeRegion>>)e.Value;
_regionsDictionary.OnDeserialization( this);
break;
By the way, it is not always necessary to implement ISerializable. For example, if you simplify
RectangleRegion removing ISerializable and two special serialisation members, then it will work too.