Must implement ISerializable on Entity to properly serialize Entities, plus everything an Entity can reference.

LibBSP/Source/Structs/Common/Entity.cs

@@ -6,6 +6,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Text;
+using System.Runtime.Serialization;
 #if UNITY
 using UnityEngine;
 #endif
@@ -18,7 +19,7 @@ namespace LibBSP {
 	/// <summary>
 	/// Class containing all data for a single <see cref="Entity"/>, including attributes, Source Entity I/O connections and solids.
 	/// </summary>
-	[Serializable] public class Entity : Dictionary<string, string>, IComparable, IComparable<Entity> {
+	[Serializable] public class Entity : Dictionary<string, string>, IComparable, IComparable<Entity>, ISerializable {
 
 		public const char ConnectionMemberSeparater = (char)0x1B;
 
@@ -142,7 +143,7 @@ namespace LibBSP {
 				if (ContainsKey(key)) {
 					return base[key];
 				} else {
-					return string.Empty;
+					return "";
 				}
 			}
 			set { base[key] = value; }
@@ -248,6 +249,16 @@ namespace LibBSP {
 			}
 		}
 
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Entity"/> class with serialized data.
+		/// </summary>
+		/// <param name="info">A <c>SerializationInfo</c> object containing the information required to serialize the <see cref="Entity"/>.</param>
+		/// <param name="context">A <c>StreamingContext</c> structure containing the source and destination of the serialized stream associated with the <see cref="Entity"/>.</param>
+		protected Entity(SerializationInfo info, StreamingContext context) : base(info, context) {
+			connections = (List<EntityConnection>)info.GetValue("connections", typeof(List<EntityConnection>));
+			brushes = (List<MAPBrush>)info.GetValue("brushes", typeof(List<MAPBrush>));
+		}
+
 		/// <summary>
 		/// Factory method to create an <see cref="Entity"/> from a <c>string</c> "<paramref name="st"/>" where
 		/// "<paramref name="st"/>" contains all lines for the entity, including attributes, brushes, etc.
@@ -457,6 +468,7 @@ namespace LibBSP {
 			return new Vector4(results[0], results[1], results[2], results[3]);
 		}
 
+		#region IComparable
 		/// <summary>
 		/// Compares this <see cref="Entity"/> to another object. First "classname" attributes are compared, then "targetname".
 		/// Attributes are compared alphabetically. Targetnames are only compared if classnames match.
@@ -484,6 +496,22 @@ namespace LibBSP {
 			int firstTry = className.CompareTo(other.className);
 			return firstTry != 0 ? firstTry : name.CompareTo(other.name);
 		}
+		#endregion
+
+		#region ISerializable
+		/// <summary>
+		/// Implements the <c>ISerializable</c> interface and returns the data needed
+		/// to serialize the <see cref="Entity"> instance.
+		/// </summary>
+		/// <param name="info">A <c>SerializationInfo</c> object that contains the information required to serialize the <see cref="Entity"> instance.</param>
+		/// <param name="context">A <c>StreamingContext</c> structure that contains the source and destination of the serialized stream associated with the <see cref="Entity"/> instance.</param>
+		public override void GetObjectData(SerializationInfo info, StreamingContext context) {
+			base.GetObjectData(info, context);
+			info.AddValue("connections", connections, typeof(List<EntityConnection>));
+			info.AddValue("brushes", brushes, typeof(List<MAPBrush>));
+
+		}
+		#endregion
 
 		/// <summary>
 		/// Factory method for an <see cref="Entities"/> object from a <c>byte</c> array.
@@ -549,7 +577,7 @@ namespace LibBSP {
 		/// <summary>
 		/// Struct containing the fields necessary for Source entity I/O.
 		/// </summary>
-		public struct EntityConnection {
+		[Serializable] public struct EntityConnection {
 			public string name;
 			public string target;
 			public string action;

LibBSP/Source/Structs/Common/Lumps/Entities.cs

@@ -5,7 +5,7 @@ namespace LibBSP {
 	/// <summary>
 	/// Class representing a group of <see cref="Entity"/> objects. Contains helpful methods to handle Entities in the <c>List</c>.
 	/// </summary>
-	public class Entities : List<Entity> {
+	[Serializable] public class Entities : List<Entity> {
 
 		/// <summary>
 		/// Initializes a new instance of an <see cref="Entities"/> object copying a passed <c>IEnumerable</c> of <see cref="Entity"/> objects.

LibBSP/Source/Structs/MAP/MAPBrush.cs

@@ -2,13 +2,14 @@
 #define UNITY
 #endif
 
+using System;
 using System.Collections.Generic;
 
 namespace LibBSP {
 	/// <summary>
 	/// Class containing all data for a single brush, including side definitions or a patch definition.
 	/// </summary>
-	public class MAPBrush {
+	[Serializable] public class MAPBrush {
 
 		public List<MAPBrushSide> sides = new List<MAPBrushSide>(6);
 		public MAPPatch patch;

LibBSP/Source/Structs/MAP/MAPBrushSide.cs

@@ -15,7 +15,7 @@ namespace LibBSP {
 	/// <summary>
 	/// Class containing data for a brush side. Please note vertices must be set manually or generated through CSG.
 	/// </summary>
-	public class MAPBrushSide {
+	[Serializable] public class MAPBrushSide {
 
 		public Vector3[] vertices;
 		public Plane plane;

LibBSP/Source/Structs/MAP/MAPDisplacement.cs

@@ -16,7 +16,7 @@ namespace LibBSP {
 	/// <summary>
 	/// Class containing all data necessary to render a displacement from Source engine.
 	/// </summary>
-	public class MAPDisplacement {
+	[Serializable] public class MAPDisplacement {
 
 		public int power;
 		public Vector3 start;

LibBSP/Source/Structs/MAP/MAPPatch.cs

@@ -18,7 +18,7 @@ namespace LibBSP {
 	/// <summary>
 	/// Class containing all data necessary to render a Bezier patch.
 	/// </summary>
-	public class MAPPatch {
+	[Serializable] public class MAPPatch {
 
 		public UIVertex[] points;
 		public Vector2 dims;