diff --git a/.config/dotnet-tools.json b/.config/dotnet-tools.json
new file mode 100644
index 0000000..9cff1bf
--- /dev/null
+++ b/.config/dotnet-tools.json
@@ -0,0 +1,13 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "csharpier": {
+      "version": "0.30.3",
+      "commands": [
+        "dotnet-csharpier"
+      ],
+      "rollForward": false
+    }
+  }
+}
\ No newline at end of file
diff --git a/.csharpierignore b/.csharpierignore
new file mode 100644
index 0000000..d899011
--- /dev/null
+++ b/.csharpierignore
@@ -0,0 +1,5 @@
+.direnv/
+target/
+**/[Bb]in/
+**/[Oo]bj/
+.git/
diff --git a/.github/workflows/csharp.yaml b/.github/workflows/csharp.yaml
index 4f506f6..10678d8 100644
--- a/.github/workflows/csharp.yaml
+++ b/.github/workflows/csharp.yaml
@@ -13,8 +13,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4.2.0
 
+      - name: Install dotnet tools
+        run: dotnet tool restore
       - name: Check formatting
-        run: dotnet format --verify-no-changes
+        run: dotnet csharpier --check .
 
   test:
     name: Run Tests
diff --git a/did-csharp/Class1.cs b/did-csharp/Class1.cs
index 205a6cb..6d15690 100644
--- a/did-csharp/Class1.cs
+++ b/did-csharp/Class1.cs
@@ -2,8 +2,5 @@
 
 namespace did_csharp
 {
-	public class Class1
-	{
-
-	}
+	public class Class1 { }
 }
diff --git a/flake.nix b/flake.nix
index b901f70..da56f1f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -45,6 +45,11 @@
           ];
           config = {
             # allowUnfree = true;
+            permittedInsecurePackages = [
+              # Needed for roslyn-ls, see
+              # https://github.com/NixOS/nixpkgs/blob/4989a246/pkgs/by-name/ro/roslyn-ls/package.nix#L21
+              "dotnet-sdk-6.0.428"
+            ];
           };
         };
       });
diff --git a/nix/devShells.nix b/nix/devShells.nix
index d64a4c7..c0fed45 100644
--- a/nix/devShells.nix
+++ b/nix/devShells.nix
@@ -9,16 +9,23 @@ let
   rustPlatform = pkgs.makeRustPlatform {
     inherit (rustToolchain) cargo rustc;
   };
+  dotnet = (with pkgs.dotnetCorePackages;
+    # We will combine the two latest dotnet SDKs to give all tools time to
+    # upgrade
+    combinePackages [
+      sdk_9_0
+    ]);
 in
 {
   default = pkgs.mkShell {
     # These programs be available to the dev shell
     buildInputs = (with pkgs; [
       cargo-deny
-      dotnetCorePackages.sdk_9_0
+      dotnet
       mdbook
       mdbook-mermaid
       nixpkgs-fmt
+      roslyn-ls
     ]) ++ pkgs.lib.optional pkgs.stdenv.isDarwin [
       pkgs.libiconv
     ] ++ [
diff --git a/nix/inputs.nix b/nix/inputs.nix
index ff2556d..8b2317e 100644
--- a/nix/inputs.nix
+++ b/nix/inputs.nix
@@ -4,12 +4,9 @@ let
   isDarwin = (system == "aarch64-darwin" || system == "x86_64-darwin");
 in
 {
+  inherit (inputs-raw) fenix nixos-generators home-manager deploy-rs;
   self = inputs-raw.self;
   nixpkgs = if isDarwin then inputs-raw.nixpkgs-24_11-darwin else inputs-raw.nixos-24_11;
   nixpkgs-unstable = if isDarwin then inputs-raw.nixpkgs-unstable else inputs-raw.nixos-unstable;
   # fenix = if isDarwin then inputs-raw.fenix-darwin else inputs-raw.fenix-linux;
-  fenix = inputs-raw.fenix;
-  nixos-generators = inputs-raw.nixos-generators;
-  home-manager = inputs-raw.home-manager;
-  deploy-rs = inputs-raw.deploy-rs;
 }