Auto-install .NET 8 runtimes if missing

A fresh Windows Server install has neither ASP.NET Core 8 nor .NET
Desktop 8, so the Service refuses to start and the GUI fails to
launch — the symptoms link to aka.ms/dotnet-core-applaunch but it's
not obvious from the GUI itself what's wrong.

Setup now:
- Detects each runtime by looking for an 8.x folder under
  %ProgramFiles%\dotnet\shared\Microsoft.{AspNetCore,WindowsDesktop}.App
- Uses Inno Setup's built-in TDownloadWizardPage to fetch any missing
  runtime from the aka.ms redirect and runs `/install /quiet /norestart`
- Treats Microsoft's 1638 / 3010 / 1641 exit codes as success

If the box has no internet, the prereq install fails with a clear
message and a "continue anyway?" prompt. README + installation docs
list the manual download URLs and `dotnet --list-runtimes` check;
troubleshooting has a section pointing at the same fix when the
service won't start after install.

README.md

@@ -7,7 +7,7 @@ Designed for sysadmins who want to wire up tools like **Zerto pre/post scripts**
 ## Quickstart
 
 1. **Download** the latest installer: <https://github.com/recklessop/webhook-server/releases/latest>
-2. **Run it.** UAC accept → next, next, finish. Adds a Start Menu entry, registers and starts the Windows Service.
+2. **Run it.** UAC accept → next, next, finish. Adds a Start Menu entry, registers and starts the Windows Service. The installer also downloads + installs the **.NET 8 runtimes** (ASP.NET Core + Desktop) if they're missing — fresh Windows Server installs need this.
 3. **Open Webhook Server** from the Start Menu (auto-elevates).
 4. **File → New endpoint**, configure a slug + script, save, hit the URL.
 

docs/installation.md

@@ -6,10 +6,34 @@ This page covers a fresh install. If you already have Webhook Server installed,
 
 - Windows 10, Windows 11, or Windows Server 2019 / 2022 / 2025
 - Administrator rights to install the service and to run the GUI
+- **.NET 8 runtimes** (the installer downloads + installs them automatically if missing — see below)
 - (Optional, only if you publish from source) .NET 8 SDK
 
 The installer is **x64 only**. There is no x86 build.
 
+### .NET 8 runtimes
+
+Webhook Server is published as framework-dependent (so the installer stays small) and needs two .NET 8 runtimes on the target machine:
+
+| Runtime | Used by | Auto-installed by setup |
+|---|---|---|
+| ASP.NET Core 8 Runtime (`Microsoft.AspNetCore.App` 8.x) | the Service / Kestrel | Yes |
+| .NET Desktop Runtime 8 (`Microsoft.WindowsDesktop.App` 8.x) | the WPF GUI | Yes |
+
+A clean Windows Server install has neither. The installer detects what's missing and downloads + installs each one silently before copying our files. If the machine has no internet access, install them manually first:
+
+- ASP.NET Core 8 Runtime — <https://aka.ms/dotnet/8.0/aspnetcore-runtime-win-x64.exe>
+- .NET Desktop Runtime 8 — <https://aka.ms/dotnet/8.0/windowsdesktop-runtime-win-x64.exe>
+
+Run each with `/install /quiet /norestart` for unattended installs, or just double-click. A reboot is rarely required.
+
+To check what's already installed:
+
+```powershell
+dotnet --list-runtimes
+# expect to see Microsoft.AspNetCore.App 8.x.y and Microsoft.WindowsDesktop.App 8.x.y
+```
+
 ## 1. Download
 
 Grab the latest installer from the GitHub Releases page:

docs/troubleshooting.md

@@ -38,6 +38,28 @@ You launched the GUI without elevation. The admin pipe ACL is `SYSTEM` + `Admini
 
 **Fix in v0.1.0**: right-click the Start Menu shortcut → **Run as administrator**, or upgrade.
 
+### Service won't start after install / GUI says "Disconnected" with no obvious error
+
+If `Get-Service WebhookServer` shows it stopped and `Start-Service WebhookServer` fails, or the GUI itself won't even launch, you're probably missing a .NET 8 runtime. The v0.1.4+ installer auto-fetches them, but a clean Windows Server box might still hit this if the install was offline or used an older installer.
+
+Check what's installed:
+
+```powershell
+dotnet --list-runtimes
+```
+
+You need both:
+
+- `Microsoft.AspNetCore.App 8.x.y` — for the Service
+- `Microsoft.WindowsDesktop.App 8.x.y` — for the GUI
+
+If either is missing, install from:
+
+- ASP.NET Core 8 Runtime — <https://aka.ms/dotnet/8.0/aspnetcore-runtime-win-x64.exe>
+- .NET Desktop Runtime 8 — <https://aka.ms/dotnet/8.0/windowsdesktop-runtime-win-x64.exe>
+
+Re-run with `/install /quiet /norestart` for unattended installs. Then `Start-Service WebhookServer`.
+
 ### "Connection refused" hitting the hook URL
 
 Three possibilities, in order of probability:

installer/webhook-server.iss

@@ -86,6 +86,17 @@ Filename: "powershell.exe"; \
     RunOnceId: "RemoveWebhookService"
 
 [Code]
+const
+  // aka.ms redirects to the latest 8.0.x patch. Inno Setup's downloader
+  // follows redirects via the Windows HTTP stack.
+  AspNetCore8Url  = 'https://aka.ms/dotnet/8.0/aspnetcore-runtime-win-x64.exe';
+  WinDesktop8Url  = 'https://aka.ms/dotnet/8.0/windowsdesktop-runtime-win-x64.exe';
+  AspNetCore8File = 'aspnetcore-runtime-8.0-win-x64.exe';
+  WinDesktop8File = 'windowsdesktop-runtime-8.0-win-x64.exe';
+
+var
+  DownloadPage: TDownloadWizardPage;
+
 function ServiceExists(): Boolean;
 var
   ResultCode: Integer;
@@ -96,6 +107,119 @@ begin
   Result := (ResultCode = 0);
 end;
 
+// True if a Microsoft.* shared-framework directory under
+// %ProgramFiles%\dotnet\shared contains at least one 8.x.y subfolder.
+function HasDotNet8(const RuntimeName: String): Boolean;
+var
+  rec: TFindRec;
+  base: String;
+begin
+  Result := False;
+  base := ExpandConstant('{commonpf}\dotnet\shared\') + RuntimeName;
+  if not DirExists(base) then Exit;
+  if FindFirst(base + '\8.*', rec) then
+  try
+    repeat
+      if (rec.Name <> '.') and (rec.Name <> '..') and
+         DirExists(base + '\' + rec.Name) then begin
+        Result := True;
+        Exit;
+      end;
+    until not FindNext(rec);
+  finally
+    FindClose(rec);
+  end;
+end;
+
+function NeedsAspNet8(): Boolean;
+begin
+  Result := not HasDotNet8('Microsoft.AspNetCore.App');
+end;
+
+function NeedsWinDesktop8(): Boolean;
+begin
+  Result := not HasDotNet8('Microsoft.WindowsDesktop.App');
+end;
+
+procedure InitializeWizard;
+begin
+  DownloadPage := CreateDownloadPage(
+    'Downloading prerequisites',
+    'Webhook Server needs the .NET 8 runtimes. Setup is fetching them now.',
+    nil);
+end;
+
+// Runs a downloaded runtime installer silently. Treats Microsoft's
+// "success but reboot pending" / "newer already installed" exit codes
+// as successes so we don't fail the whole install over a benign result.
+function RunRuntimeInstaller(const FileName, DisplayName: String): String;
+var
+  resultCode: Integer;
+  fullPath: String;
+begin
+  Result := '';
+  fullPath := ExpandConstant('{tmp}\') + FileName;
+  if not Exec(fullPath, '/install /quiet /norestart', '', SW_HIDE,
+              ewWaitUntilTerminated, resultCode) then begin
+    Result := 'Could not launch the ' + DisplayName + ' installer.';
+    Exit;
+  end;
+  case resultCode of
+    0, 1638, 3010, 1641: ;
+  else
+    Result := DisplayName + ' installer failed (exit code ' +
+              IntToStr(resultCode) + ').';
+  end;
+end;
+
+function NextButtonClick(CurPageID: Integer): Boolean;
+var
+  errMsg: String;
+begin
+  Result := True;
+  if CurPageID <> wpReady then Exit;
+  if not (NeedsAspNet8 or NeedsWinDesktop8) then Exit;
+
+  DownloadPage.Clear;
+  if NeedsAspNet8 then
+    DownloadPage.Add(AspNetCore8Url, AspNetCore8File, '');
+  if NeedsWinDesktop8 then
+    DownloadPage.Add(WinDesktop8Url, WinDesktop8File, '');
+  DownloadPage.Show;
+  try
+    try
+      DownloadPage.Download;
+    except
+      if MsgBox('Failed to download the .NET 8 runtimes:' + #13#10#13#10 +
+                GetExceptionMessage + #13#10#13#10 +
+                'Continue installing anyway? Webhook Server will not start ' +
+                'until the runtimes are installed manually.',
+                mbError, MB_YESNO) = IDNO then
+        Result := False;
+      Exit;
+    end;
+  finally
+    DownloadPage.Hide;
+  end;
+
+  if NeedsAspNet8 then begin
+    errMsg := RunRuntimeInstaller(AspNetCore8File, 'ASP.NET Core 8 Runtime');
+    if errMsg <> '' then begin
+      MsgBox(errMsg, mbError, MB_OK);
+      Result := False;
+      Exit;
+    end;
+  end;
+  if NeedsWinDesktop8 then begin
+    errMsg := RunRuntimeInstaller(WinDesktop8File, '.NET Desktop Runtime 8');
+    if errMsg <> '' then begin
+      MsgBox(errMsg, mbError, MB_OK);
+      Result := False;
+      Exit;
+    end;
+  end;
+end;
+
 function PrepareToInstall(var NeedsRestart: Boolean): String;
 var
   ResultCode: Integer;