From 688d6d83cc0d8f70ced6821a1bd0a5e12472e26f Mon Sep 17 00:00:00 2001
From: Florian Rappl <mail@florian-rappl.de>
Date: Sun, 2 Nov 2025 23:35:46 +0100
Subject: [PATCH] Fixed single instance behavior

---
 Changelog.md                                  |  1 +
 src/ElectronNET.API/Runtime/StartupManager.cs | 12 ++++++++++--
 src/ElectronNET.Host/main.js                  |  2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index 3d714eb..cd4caa0 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -4,6 +4,7 @@
 
 - Updated `PrintToPDFOptions` to also allow specifying the `PageSize` with an object (#769)
 - Updated splashscreen image to have 0 margin (#622)
+- Fixed single instance behavior using the `ElectronSingleInstance` property (#901)
 - Added option to use `ElectronSplashScreen` with an HTML file (#799)
 - Added option to provide floating point value as aspect ratios with `SetAspectRatio` (#793)
 
diff --git a/src/ElectronNET.API/Runtime/StartupManager.cs b/src/ElectronNET.API/Runtime/StartupManager.cs
index 147c452..67c6f4c 100644
--- a/src/ElectronNET.API/Runtime/StartupManager.cs
+++ b/src/ElectronNET.API/Runtime/StartupManager.cs
@@ -136,18 +136,26 @@
                 buildInfo.ElectronExecutable = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.ElectronExecutable))?.Value;
                 buildInfo.ElectronVersion = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.ElectronVersion))?.Value;
                 buildInfo.RuntimeIdentifier = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.RuntimeIdentifier))?.Value;
-                buildInfo.ElectronSingleInstance = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.ElectronSingleInstance))?.Value;
                 buildInfo.Title = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.Title))?.Value;
                 buildInfo.Version = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.Version))?.Value;
                 buildInfo.BuildConfiguration = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.BuildConfiguration))?.Value;
                 var isAspNet = attributes.FirstOrDefault(e => e.Key == "IsAspNet")?.Value;
+                var isSingleInstance = attributes.FirstOrDefault(e => e.Key == nameof(buildInfo.ElectronSingleInstance))?.Value;
+                var httpPort = attributes.FirstOrDefault(e => e.Key == "AspNetHttpPort")?.Value;
 
                 if (isAspNet?.Length > 0 && bool.TryParse(isAspNet, out var res) && res)
                 {
                     ElectronNetRuntime.DotnetAppType = DotnetAppType.AspNetCoreApp;
                 }
 
-                var httpPort = attributes.FirstOrDefault(e => e.Key == "AspNetHttpPort")?.Value;
+                if (isSingleInstance?.Length > 0 && bool.TryParse(isSingleInstance, out var res) && res)
+                {
+                    buildInfo.ElectronSingleInstance = "yes";
+                }
+                else
+                {
+                    buildInfo.ElectronSingleInstance = "no";
+                }
 
                 if (httpPort?.Length > 0 && int.TryParse(httpPort, out var port))
                 {
diff --git a/src/ElectronNET.Host/main.js b/src/ElectronNET.Host/main.js
index e0879c7..1c56801 100644
--- a/src/ElectronNET.Host/main.js
+++ b/src/ElectronNET.Host/main.js
@@ -92,7 +92,7 @@ app.on('will-finish-launching', () => {
 
 const manifestJsonFile = require(manifestJsonFilePath);
 
-if (manifestJsonFile.singleInstance) {
+if (manifestJsonFile.singleInstance === "yes") {
     const mainInstance = app.requestSingleInstanceLock();
     app.on('second-instance', (events, args = []) => {
         args.forEach((parameter) => {