Extract file preamble generation into CodeGenerator.

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -147,7 +147,7 @@ namespace CppSharp.Generators.CSharp
 
         public override void Process()
         {
-            GenerateHeader();
+            GenerateFilePreamble();
 
             PushBlock(CSharpBlockKind.Usings);
             WriteLine("using System;");
@@ -187,18 +187,6 @@ namespace CppSharp.Generators.CSharp
             }
         }
 
-        public void GenerateHeader()
-        {
-            PushBlock(BlockKind.Header);
-            WriteLine("//----------------------------------------------------------------------------");
-            WriteLine("// <auto-generated>");
-            WriteLine("// This is autogenerated code by CppSharp.");
-            WriteLine("// Do not edit this file or all your changes will be lost after re-generation.");
-            WriteLine("// </auto-generated>");
-            WriteLine("//----------------------------------------------------------------------------");
-            PopBlock();
-        }
-
         public override bool VisitDeclContext(DeclarationContext context)
         {
             var isNamespace = context is Namespace;

src/Generator/Generators/CodeGenerator.cs

@@ -40,6 +40,18 @@ namespace CppSharp.Generators
             return base.Generate();
         }
 
+        public virtual void GenerateFilePreamble()
+        {
+            PushBlock(BlockKind.Header);
+            WriteLine("//----------------------------------------------------------------------------");
+            WriteLine("// <auto-generated>");
+            WriteLine("// This is autogenerated code by CppSharp.");
+            WriteLine("// Do not edit this file or all your changes will be lost after re-generation.");
+            WriteLine("// </auto-generated>");
+            WriteLine("//----------------------------------------------------------------------------");
+            PopBlock();
+        }
+
         #region Visitor methods
 
         public virtual bool VisitDeclaration(Declaration decl)