using ICSharpCode.Decompiler;
using ICSharpCode.Decompiler.CSharp;
using ICSharpCode.Decompiler.TypeSystem;

var decompiler = new CSharpDecompiler(fileName, new DecompilerSettings());

var decompiler = new CSharpDecompiler("Demo.ConsoleApp.exe", new DecompilerSettings());
var name = new FullTypeName("Demo.ConsoleApp.Test+NestedClassTest");
Console.WriteLine(decompiler.DecompileTypeAsString(name));

var decompiler = new CSharpDecompiler("Demo.ConsoleApp.exe", new DecompilerSettings());
var name = new FullTypeName("Demo.ConsoleApp.Test+NestedClassTest");
ITypeDefinition typeInfo = decompiler.TypeSystem.FindType(name).GetDefinition();
var tokenOfFirstMethod = typeInfo.Methods.First().MetadataToken;
Console.WriteLine(decompiler.DecompileAsString(tokenOfFirstMethod));

ITypeDefinition type = decompiler.TypeSystem.FindType(nameOfUniResolver).GetDefinition();
var module = type.ParentModule.PEFile;

var icsdns = decompiler.TypeSystem.RootNamespace;
foreach (var ns in icsdns.ChildNamespaces) Console.WriteLine(ns.FullName);

// ICSharpCode.Decompiler.TypeSystem is the first namespace
var typesInNamespace = icsdns.ChildNamespaces.First().Types;