When I navigate to C:\Windows\System32, I can see that it contains Query.exe
However, if I use IL DASM and go to the same location, Query.exe is missing along with a handful of other files, even though I have selected Any Types for the file types
At first I thought it might be because query.exe is not available to be decompiled, but I am able to see other .exes in there which are also not available to be decompiled by IL DASM (e.g. calc.exe)
Why does IL DASM behave like this?
Always beware the file system redirector. You are running the 32-bit version of ildasm.exe so it gets redirected to the home for 32-bit executables, c:\windows\syswow64.
A simple workaround is to navigate to c:\windows\sysnative instead. Or to use the 64-bit version of ildasm.exe, say C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools\x64\ildasm.exe. Or to configure the Visual Studio Command Prompt (aka vcvarsall) if you use that, pass the "x64" argument.
Query.exe is not a .NET assembly so there isn't much to see.