JetBrains.dotPeek
Free .NET Decompiler and Assembly Browser
Decompile .NET assemblies to C#
dotPeek is a free-of-charge standalone tool based on ReSharper's bundled decompiler. It can reliably decompile any .NET assembly into equivalent C# or IL code.
The decompiler supports multiple formats including libraries (.dll), executables (.exe), and Windows metadata files (.winmd).