If PowerShell is not installed the Add Package Reference dialog will not install the package using the console.

src/AddIns/Misc/PackageManagement/Project/Src/PackageActionRunner.cs

@@ -2,25 +2,60 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using ICSharpCode.PackageManagement.Scripting;
+using NuGet;
 
 namespace ICSharpCode.PackageManagement
 {
 	public class PackageActionRunner : IPackageActionRunner
 	{
 		IPackageActionRunner consolePackageActionRunner;
+		IPackageManagementEvents packageManagementEvents;
+		IPowerShellDetection powerShellDetection;
 		
-		public PackageActionRunner(IPackageActionRunner consolePackageActionRunner)
+		public PackageActionRunner(
+			IPackageActionRunner consolePackageActionRunner,
+			IPackageManagementEvents packageManagementEvents)
+			: this(consolePackageActionRunner, packageManagementEvents, new PowerShellDetection())
+		{
+		}
+		
+		public PackageActionRunner(
+			IPackageActionRunner consolePackageActionRunner,
+			IPackageManagementEvents packageManagementEvents,
+			IPowerShellDetection powerShellDetection)
 		{
 			this.consolePackageActionRunner = consolePackageActionRunner;
+			this.packageManagementEvents = packageManagementEvents;
+			this.powerShellDetection = powerShellDetection;
 		}
 		
 		public void Run(ProcessPackageAction action)
 		{
-			if (action.HasPackageScriptsToRun()) {
+			if (RunActionInConsole(action)) {
 				consolePackageActionRunner.Run(action);
 			} else {
 				action.Execute();
 			}
 		}
+		
+		bool RunActionInConsole(ProcessPackageAction action)
+		{
+			if (action.HasPackageScriptsToRun()) {
+				if (powerShellDetection.IsPowerShell2Installed()) {
+					return true;
+				} else {
+					ReportPowerShellIsNotInstalled();
+				}
+			}
+			return false;
+		}
+		
+		void ReportPowerShellIsNotInstalled()
+		{
+			string message = 
+				"PowerShell is not installed. PowerShell scripts will not be run for the package.";
+			packageManagementEvents.OnPackageOperationMessageLogged(MessageLevel.Warning, message);
+		}
 	}
 }

src/AddIns/Misc/PackageManagement/Project/Src/PackageManagementServices.cs

@@ -32,7 +32,7 @@ namespace ICSharpCode.PackageManagement
 			runPackageInitializationScripts = new RunPackageInitializationScriptsOnSolutionOpen(projectService);
 			resetPowerShellWorkingDirectory = new ResetPowerShellWorkingDirectoryOnSolutionClosed(projectService, ConsoleHost);
 			var consolePackageActionRunner = new ConsolePackageActionRunner(ConsoleHost, packageActionsToRun);
-			packageActionRunner = new PackageActionRunner(consolePackageActionRunner);
+			packageActionRunner = new PackageActionRunner(consolePackageActionRunner, packageManagementEvents);
 		}
 		
 		public static PackageManagementOptions Options {

src/AddIns/Misc/PackageManagement/Project/Src/Scripting/PowerShellDetection.cs

@@ -12,17 +12,26 @@ namespace ICSharpCode.PackageManagement.Scripting
 			@"SOFTWARE\Microsoft\PowerShell\1\PowerShellEngine";
 		
 		public static readonly string PowerShellVersionRegistryValueName =
-			"PowerShellVersion2";
+			"PowerShellVersion";
+		
+		public bool? installed;
 		
 		public bool IsPowerShell2Installed()
+		{
+			if (!installed.HasValue) {
+				CheckIfPowerShell2IsInstalled();
+			}
+			return installed.Value;
+		}
+		
+		void CheckIfPowerShell2IsInstalled()
 		{
 			RegistryKey key = OpenPowerShellRegistryKey();
 			if (key != null) {
 				using (key) {
-					return IsPowerShell2Installed(key);
+					installed = IsPowerShell2Installed(key);
 				}
 			}
-			return false;
 		}
 		
 		RegistryKey OpenPowerShellRegistryKey()

src/AddIns/Misc/PackageManagement/Test/Src/PackageActionRunnerTests.cs

@@ -17,11 +17,15 @@ namespace PackageManagement.Tests
 		FakePackageActionRunner fakeConsoleActionRunner;
 		PackageActionRunner runner;
 		FakeInstallPackageAction fakeAction;
+		FakePowerShellDetection powerShellDetection;
+		FakePackageManagementEvents fakeEvents;
 		
 		void CreateRunner()
 		{
 			fakeConsoleActionRunner = new FakePackageActionRunner();
-			runner = new PackageActionRunner(fakeConsoleActionRunner);	
+			powerShellDetection = new FakePowerShellDetection();
+			fakeEvents = new FakePackageManagementEvents();
+			runner = new PackageActionRunner(fakeConsoleActionRunner, fakeEvents, powerShellDetection);
 		}
 		
 		void CreateInstallActionWithNoPowerShellScripts()
@@ -67,6 +71,7 @@ namespace PackageManagement.Tests
 		{
 			CreateRunner();
 			CreateInstallActionWithOnePowerShellScript();
+			powerShellDetection.IsPowerShell2InstalledReturnValue = true;
 			Run();
 			
 			ProcessPackageAction action = fakeConsoleActionRunner.ActionPassedToRun;
@@ -79,11 +84,42 @@ namespace PackageManagement.Tests
 		{
 			CreateRunner();
 			CreateInstallActionWithOnePowerShellScript();
+			powerShellDetection.IsPowerShell2InstalledReturnValue = true;
 			Run();
 			
 			bool executed = fakeAction.IsExecuteCalled;
 			
 			Assert.IsFalse(executed);
 		}
+		
+		[Test]
+		public void Run_InstallActionHasOnePowerShellScriptAndPowerShellIsNotInstalled_ActionIsExecutedDirectly()
+		{
+			CreateRunner();
+			CreateInstallActionWithOnePowerShellScript();
+			powerShellDetection.IsPowerShell2InstalledReturnValue = false;
+			
+			Run();
+			
+			bool executed = fakeAction.IsExecuteCalled;
+			
+			Assert.IsTrue(executed);
+		}
+		
+		[Test]
+		public void Run_InstallActionHasOnePowerShellScriptAndPowerShellIsNotInstalled_MessageIsReportedThatPowerShellScriptsCannotBeRun()
+		{
+			CreateRunner();
+			CreateInstallActionWithOnePowerShellScript();
+			powerShellDetection.IsPowerShell2InstalledReturnValue = false;
+			
+			Run();
+			
+			string message = fakeEvents.FormattedStringPassedToOnPackageOperationMessageLogged;
+			string expectedMessage = 
+				"PowerShell is not installed. PowerShell scripts will not be run for the package.";
+			
+			Assert.AreEqual(expectedMessage, message);
+		}
 	}
 }