CLI generator needs first function parameter.

src/Generator/Passes/FunctionToInstanceMethodPass.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using CppSharp.AST;
+using CppSharp.Generators;
 
 namespace CppSharp.Passes
 {
@@ -51,13 +52,16 @@ namespace CppSharp.Passes
                     Access = AccessSpecifier.Public,
                     Kind = CXXMethodKind.Normal,
                     ReturnType = function.ReturnType,
-                    Parameters = function.Parameters.Skip(1).ToList(),
+                    Parameters = function.Parameters,
                     CallingConvention = function.CallingConvention,
                     IsVariadic = function.IsVariadic,
                     IsInline = function.IsInline,
                     Conversion = MethodConversionKind.FunctionToInstanceMethod
                 };
 
+            if (Driver.Options.GeneratorKind == LanguageGeneratorKind.CSharp)
+                method.Parameters = method.Parameters.Skip(0).ToList();
+
             @class.Methods.Add(method);
 
             Console.WriteLine("Instance method: {0}::{1}", @class.Name,