ILSpy is an assembly browser and decompiler. Here we will go through installing and using ILSpy.
First, download the binaries from the ILSpy website:
This will download a ZIP file.
Extract the file:
Run the ISpy.exe:
Click to open a file:
Here I have selected an exe compiled from code I previously wrote. You can see we can now see the decompiled code within ILSpy: