diff --git a/nonguix/build-system/dotnet.scm b/nonguix/build-system/dotnet.scm
new file mode 100644
index 00000000..5286c84d
--- /dev/null
+++ b/nonguix/build-system/dotnet.scm
@@ -0,0 +1,97 @@
+(define-module (nonguix nonguix build-system dotnet)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix gexp)
+  #:use-module (guix monads)
+  #:use-module (guix derivations)
+  #:use-module (guix search-paths)
+  #:use-module (guix build-system)
+  #:use-module (guix build-system gnu)
+  #:use-module (guix build-system copy)
+  #:use-module (guix packages)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:export (%dotnet-build-system-modules
+            default-dotnet
+            lower
+            dotnet-build
+            dotnet-build-system))
+
+(define %dotnet-build-system-modules
+  `((nonguix build dotnet-build-system)
+    (gnu build utils)))
+
+(define (default-dotnet)
+  (let ((module (resolve-interface '(nongnu packages dotnet))))
+    (module-ref module 'dotnet)))
+
+(define* (lower name
+                #:key source inputs native-inputs outputs system target
+                (dotnet (default-dotnet))
+                #:allow-other-keys
+                #:rest arguments)
+  "Return a bag for NAME."
+  (define private-keywords
+    '(#:target #:inputs #:native-inputs))
+  (and (not target)
+       (bag
+        (name name)
+        (system system)
+        (host-inputs `(("dotnet" ,dotnet)
+                       ,@inputs
+                       ,@(standard-packages)))
+        (build-inputs `(,@native-inputs))
+        (outputs outputs)
+        (build dotnet-build)
+        (arguments (strip-keyword-arguments private-keywords arguments)))))
+
+(define* (dotnet-build name inputs
+                       #:key
+                       guile source
+                       (outputs '("out"))
+                       (project-name #f)
+                       (nuget? #f)
+                       (self-contained? #t)
+                       (strip-debug-symbols? #t)
+                       (search-paths '())
+                       (path-shebangs? #t)
+                       (phases '(@ (nonguix build dotnet-build-system) %standard-phases))
+                       (system (%current-system))
+                       (imported-modules %dotnet-build-system-modules)
+                       (modules '((nonguix build dotnet-build-system)
+                                  (guix build utils)))
+                       (substitutable? #t)
+                       allowed-references
+                       disallowed-references)
+  "Build SOURCE using DOTNET, and with INPUTS."
+  (define builder
+    (with-imported-modules imported-modules
+                           #~(begin
+                               (use-modules #$@modules)
+                               #$(with-build-variables inputs outputs
+                                                       #~(dotnet-build #:source #+source
+                                                                       #:system #$system
+                                                                       #:outputs %outputs
+                                                                       #:inputs %build-inputs
+                                                                       #:project-name #$project-name
+                                                                       #:nuget? #$nuget?
+                                                                       #:self-contained? #$self-contained?
+                                                                       #:strip-debug-symbols? #$strip-debug-symbols?
+                                                                       #:search-paths '#$(map search-path-specification->sexp search-paths)
+                                                                       #:phases #$phases
+                                                                       #:patch-shebangs? #$patch-shebangs?)))))
+  (mlet %store-monad ((guile (package->derivation (or guiled (default-guile))
+                                                  system #:graft? #f)))
+        (gexp->derivation name builder
+                          #:system system
+                          #:target #f
+                          #:substitutable substitutable?
+                          #:allowed-references allowed-references
+                          #:disallowed-references disallowed-references
+                          #:guile-for-build guile)))
+
+(define dotnet-build-system
+  (build-system
+   (name 'dotnet)
+   (description "")
+   (lower lower)))
diff --git a/nonguix/build/dotnet-build-system.scm b/nonguix/build/dotnet-build-system.scm
new file mode 100644
index 00000000..dd65dd68
--- /dev/null
+++ b/nonguix/build/dotnet-build-system.scm
@@ -0,0 +1,59 @@
+(define-module (build dotnet-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 match)
+  #:export (%standard-phases
+            dotnet-build))
+
+(define* (dotnet-env #:allow-other-keys)
+  (let* ((directory (or (getenv "TMPDIR") "/tmp"))
+         (template (string-append directory "/dotnet-fake-home.XXXXXX"))
+         (home (mkdtemp template)))
+    ;; Dotnet expects a writeable home directory for it's configuration files.
+    (setenv "HOME" home)
+    ;; Don't try to expand NuGetFallbackFolder to disk
+    (setenv "DOTNET_SKIP_FIRST_TIME_EXPERIENCE" "1")
+    ;; Disable the welcome message
+    (setenv "DOTNET_NOLOGO" "1")
+    (setenv "DOTNET_CLI_TELEMETRY_OPTOUT" "1")))
+
+(define* (copy-nuget-inputs #:key inputs #:allow-other-keys)
+  "Link nuget inputs into a central place so DOTNET can restore them."
+  (define (copy-input input)
+    (copy-file input (string-append "./nugets/" (strip-store-file-name input))))
+  (begin
+    (mkdir "nugets")
+    (for-each copy-input inputs)))
+
+(define* (restore-nuget-inputs #:key inputs #:allow-other-keys)
+  "Run DOTNET restore --source ./nugets"
+  (invoke "dotnet" "restore" "--source" "./nugets"))
+
+(define* (publish #:key output (project-name #f) (nuget? #f) (self-contained? #t) (strip-debug-symbols? #t) #:allow-other-keys)
+  "Run DOTNET publish or DOTNET pack"
+  (define arguments `(,@(if nuget? "pack" "publish")
+                      ,@(if project-name (list project-name) '())
+                      "--configuration" "Release"
+                      ;; don't try to access nuget.org, use local cache prepared in restore-nuget-inputs
+                      "--no-restore"
+                      ,@(if self-contained? '("--self-contained") '())
+                      ;; TODO cross-compilation
+                      "--target" "linux-x64"
+                      "-p:UseAppHost=true"
+                      ,@(if strip-debug-symbols? '("-p:DebugSymbols=false" "-p:DebugType=none") '())
+                      "--output" output)))
+
+(define %standard-phases
+  (modify-phases gnu:%standard-phases)
+  (delete 'bootstrap)
+  (delete 'configure)
+  (delete 'build)
+  (add-before 'check dotnet-env)
+  (add-before 'check copy-nuget-inputs)
+  (add-before 'check publish)
+  (replace 'install publish))
+
+(define* (dotnet-build #:key inputs (phases %standard-phases)
+                       #:allow-other-keys #:rest args)
+  "Build the given package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))