When loading the solution:

* Do not show installed extensions
* Do not offer installation if all extensions are installed

Author: loop8ack

src/ExtensionManager/Features/Install/InstallFeatureBase.cs

@@ -54,10 +54,10 @@ public async Task ExecuteAsync()
         var manifest = await ManifestService.ReadAsync(filePath).ConfigureAwait(false);
         var extensionsToInstall = await CreateExtensionsToInstallListAsync(manifest.Extensions).ConfigureAwait(false);
 
-        await ShowInstallDialogAsync(manifest, this, extensionsToInstall);
+        await ShowInstallDialogAsync(manifest, this, extensionsToInstall.ToList());
     }
 
-    private async Task<IReadOnlyList<VSExtensionToInstall>> CreateExtensionsToInstallListAsync(IEnumerable<IVSExtension> toInstall)
+    protected virtual async Task<IEnumerable<VSExtensionToInstall>> CreateExtensionsToInstallListAsync(IEnumerable<IVSExtension> toInstall)
     {
         var installed = await Extensions.GetInstalledExtensionsAsync().ConfigureAwait(false);
         var gallery = await Extensions.GetGalleryExtensionsAsync(toInstall.Select(x => x.Id)).ConfigureAwait(false);
@@ -75,8 +75,7 @@ private async Task<IReadOnlyList<VSExtensionToInstall>> CreateExtensionsToInstal
 
         return toInstall
             .Distinct(ExtensionEqualityComparer.Instance)
-            .Select(x => new VSExtensionToInstall(x, statuses[x.Id]))
-            .ToList();
+            .Select(x => new VSExtensionToInstall(x, statuses[x.Id]));
     }
 
     async Task IInstallWorker.InstallAsync(IManifest manifest, IReadOnlyCollection<IVSExtension> extensions, bool systemWide, IProgress<ProgressStep<InstallStep>> progress, CancellationToken cancellationToken)

src/ExtensionManager/Features/Install/InstallForSolutionFeature.cs

@@ -1,6 +1,7 @@
 using ExtensionManager.Manifest;
 using ExtensionManager.UI;
 using ExtensionManager.UI.Worker;
+using ExtensionManager.VisualStudio.Extensions;
 using ExtensionManager.VisualStudio.Solution;
 
 namespace ExtensionManager.Features.Install;
@@ -18,6 +19,19 @@ public InstallForSolutionFeature(Args args, IVSSolutions solutions)
     protected override async Task<string?> GetFilePathAsync()
         => await _solutions.GetCurrentSolutionExtensionsManifestFilePathAsync(MessageBox);
 
+    protected override async Task<IEnumerable<VSExtensionToInstall>> CreateExtensionsToInstallListAsync(IEnumerable<IVSExtension> toInstall)
+    {
+        var extensions = await base.CreateExtensionsToInstallListAsync(toInstall);
+
+        return extensions
+            .Where(x => x.Status != VSExtensionStatus.Installed);
+    }
+
     protected override async Task ShowInstallDialogAsync(IManifest manifest, IInstallWorker worker, IReadOnlyCollection<VSExtensionToInstall> extensions)
-        => await DialogService.ShowInstallForSolutionDialogAsync(worker, manifest, extensions);
+    {
+        if (extensions.Count == 0)
+            return;
+
+        await DialogService.ShowInstallForSolutionDialogAsync(worker, manifest, extensions);
+    }
 }