Updated C# and .NET docs supplement (markdown)

C#-and-.NET-docs-supplement.md

@@ -1,5 +1,5 @@
 To save us repeating our complaints about the lack of proper documentation under each section, let's agree to gather all the frustration here:
-> AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+> AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
 
 ## Deceptive collection type names
 
@@ -11,6 +11,14 @@ To save us repeating our complaints about the lack of proper documentation under
 
 see [feature matrix](https://github.com/TASEmulators/BizHawk/wiki/Available-C%23-and-.NET-features) page
 
+## MSBuild `Condition` placement
+
+On (older versions of?) VS, `Condition` is ignored if placed on a property. Create a new `<PropertyGroup/>`.
+
+## MSBuild property evaluation execution order
+
+When `<Import/>`ing a `.props` file, `ProjectDir` is unset (but `SolutionDir` *is* set, if applicable). Use `MSBuildProjectDirectory`.
+
 ## `String.GetHashCode` stability
 
 The `GetHashCode` implementation for strings does not reflect the string's contents, and as such, the hash not stable between program instances.