Deserialized

class SomeClass {
	public string StringTest;
	public int IntTest;
}

Document document = new Document();
document.add('StringTest', someClassInstance.StringTest);
document.add('IntTest', someClassInstance.IntTest);

class SomeClass : DocumentConverter {
	[Attributes.DefaultValue("Default StringTest value!")]
	public string StringTest;
	[Attributes.DefaultValue(16)]
	public int IntTest;
}

Document document = someClassInstance.ToMongoDocument();

SomeClass someOtherClassInstance = new SomeClass();
omeOtherClassInstance .FromMongoDocument(someDocumentObject);

using System;

namespace MyApp.Attributes
{
    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false)]
    class DefaultValueAttribute : Attribute
    {
        private readonly object _value;
 
        public DefaultValueAttribute(object Value)
        {
            _value = Value;
        }
 
        public object GetDefaultValue()
        {
            return _value;
        }
    }
}

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using MyApp.Classes.Attributes;
using MongoDB.Driver;
 
namespace MyApp.Classes
{
    public class DocumentConverter
    {
        public void FromMongoDocument(Document document)
        {
            foreach (DictionaryEntry kvp in document)
            {
                object propertyValue;
                if (kvp.Value != null && (kvp.Value.GetType() == typeof(Document)))
                {
                    // We have a document object - Now lets get a reference to the class property's type
                    var propertyType = GetType().GetProperty(kvp.Key.ToString()).PropertyType;
 
                    // create new instance of that class
                    var propertyInstance = Activator.CreateInstance(propertyType);
 
                    // call FromMongoDocument on that class and pass in the document
                    MethodInfo method = propertyInstance.GetType().GetMethod("FromMongoDocument");
                    method.Invoke(propertyInstance, new[] { kvp.Value });
 
                    propertyValue = propertyInstance;
                }
                else
                {
                    // This is not a Document so lets just assign the value
                    propertyValue = kvp.Value;
                }
 
                GetType().GetProperty(kvp.Key.ToString()).SetValue(this, propertyValue, null);
            }
 
        }
 
        public Document ToMongoDocument()
        {
            Document document = new Document();
 
            foreach (PropertyInfo property in GetType().GetProperties())
            {
                // Get the value of this property
                object propertyValue = property.GetValue(this, null);
 
                // If this value is null, then lets try to see if there is a default value attribute and assign that
                if (propertyValue == null)
                {
                    object[] attributes = property.GetCustomAttributes(typeof(DefaultValueAttribute), true);
                    foreach (DefaultValueAttribute defaultValue in attributes.Cast<defaultvalueattribute>())
                    {
                        propertyValue = defaultValue.GetDefaultValue();
                    }
                    document.Add(property.Name, propertyValue);
                }
                else
                {
                    // We have a property, now lets see if this property has a ToMongoDocument method
                    MethodInfo method = propertyValue.GetType().GetMethod(&quot;ToMongoDocument&quot;);
 
                    if (method == null)
                    {
                        document.Add(property.Name, property.GetValue(this, null));
                    }
                    else
                    {
                        document.Add(property.Name, method.Invoke(propertyValue, null));
                    }
                }
            }
            return document;
        }
    }
}