oh dear

mscorlib/System/Runtime/Serialization/OptionalFieldAttribute.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Runtime.InteropServices;
+using Cpp2IlInjected;
+
+namespace System.Runtime.Serialization
+{
+	/// <summary>Specifies that a field can be missing from a serialization stream so that the <see cref="T:System.Runtime.Serialization.Formatters.Binary.BinaryFormatter" /> and the <see cref="T:System.Runtime.Serialization.Formatters.Soap.SoapFormatter" /> does not throw an exception.</summary>
+	// Token: 0x02000451 RID: 1105
+	[Token(Token = "0x2000451")]
+	[ComVisible(true)]
+	[AttributeUsage(AttributeTargets.Field)]
+	public sealed class OptionalFieldAttribute : Attribute
+	{
+		/// <summary>Initializes a new instance of the <see cref="T:System.Runtime.Serialization.OptionalFieldAttribute" /> class.</summary>
+		// Token: 0x06002506 RID: 9478 RVA: 0x00002050 File Offset: 0x00000250
+		[Token(Token = "0x6002506")]
+		[Address(RVA = "0x298F6E0", Offset = "0x298E4E0", VA = "0x18298F6E0")]
+		public OptionalFieldAttribute()
+		{
+		}
+
+		/// <summary>Gets or sets a version number to indicate when the optional field was added.</summary>
+		/// <returns>The version of the <see cref="T:System.Runtime.Serialization.OptionalFieldAttribute" />.</returns>
+		// Token: 0x17000525 RID: 1317
+		// (set) Token: 0x06002507 RID: 9479 RVA: 0x00002050 File Offset: 0x00000250
+		[Token(Token = "0x17000525")]
+		public int VersionAdded
+		{
+			[Token(Token = "0x6002507")]
+			[Address(RVA = "0x298F6F0", Offset = "0x298E4F0", VA = "0x18298F6F0")]
+			set
+			{
+			}
+		}
+
+		// Token: 0x040014C9 RID: 5321
+		[global::Cpp2IlInjected.FieldOffset(Offset = "0x10")]
+		[Token(Token = "0x40014C9")]
+		private int versionAdded;
+	}
+}