oh dear

mscorlib/System/Action.cs

@@ -0,0 +1,13 @@
+using System;
+using Cpp2IlInjected;
+
+namespace System
+{
+	/// <summary>Encapsulates a method that has a single parameter and does not return a value.</summary>
+	/// <param name="obj">The parameter of the method that this delegate encapsulates.</param>
+	/// <typeparam name="T">The type of the parameter of the method that this delegate encapsulates.</typeparam>
+	// Token: 0x02000097 RID: 151
+	// (Invoke) Token: 0x06000486 RID: 1158
+	[Token(Token = "0x2000097")]
+	public delegate void Action<in T>(T obj);
+}