Cache the current open solution in the EnvDTE.DTE class.

Maintains any solution variables added between accesses to the $dte.Solution in the Powershell console.
This allows the Unity NuGet package to install without any errors.

src/AddIns/Misc/PackageManagement/Project/Src/EnvDTE/DTE.cs

@@ -13,6 +13,7 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 	{
 		IPackageManagementProjectService projectService;
 		IPackageManagementFileService fileService;
+		Solution solution;
 		
 		public DTE()
 			: this(new PackageManagementProjectService(), new PackageManagementFileService())
@@ -36,7 +37,8 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 		public Solution Solution {
 			get {
 				if (IsSolutionOpen) {
-					return new Solution(projectService);
+					CreateSolution();
+					return solution;
 				}
 				return null;
 			}
@@ -46,6 +48,21 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 			get { return projectService.OpenSolution != null; }
 		}
 		
+		void CreateSolution()
+		{
+			if (!IsOpenSolutionAlreadyCreated()) {
+				solution = new Solution(projectService);
+			}
+		}
+		
+		bool IsOpenSolutionAlreadyCreated()
+		{
+			if (solution != null) {
+				return solution.IsOpen;
+			}
+			return false;
+		}
+		
 		public ItemOperations ItemOperations { get; private set; }
 		
 		public Properties Properties(string category, string page)

src/AddIns/Misc/PackageManagement/Project/Src/EnvDTE/Solution.cs

@@ -43,5 +43,10 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 		{
 			projectService.Save(solution);
 		}
+		
+		internal bool IsSameSolution(SD.Solution solution)
+		{
+			throw new NotImplementedException();
+		}
 	}
 }

src/AddIns/Misc/PackageManagement/Test/Src/EnvDTE/DTETests.cs

@@ -20,16 +20,27 @@ namespace PackageManagement.Tests.EnvDTE
 		void CreateDTE()
 		{
 			fakeProjectService = new FakePackageManagementProjectService();
-			fakeProjectService.OpenSolution = new SD.Solution(new SD.MockProjectChangeWatcher());
+			OpenSolution(@"d:\projects\MyProject\MyProject.sln");
 			fakeFileService = new FakeFileService(null);
 			dte = new DTE(fakeProjectService, fakeFileService);
 		}
 		
+		void OpenSolution(string fileName)
+		{
+			fakeProjectService.OpenSolution = new SD.Solution(new SD.MockProjectChangeWatcher());
+			SetOpenSolutionFileName(fileName);
+		}
+		
 		void NoOpenSolution()
 		{
 			fakeProjectService.OpenSolution = null;
 		}
 		
+		void SetOpenSolutionFileName(string fileName)
+		{
+			fakeProjectService.OpenSolution.FileName = fileName;
+		}
+		
 		TestableProject AddProjectToSolution(string projectName)
 		{
 			TestableProject project = ProjectHelper.CreateTestProject(projectName);
@@ -42,7 +53,7 @@ namespace PackageManagement.Tests.EnvDTE
 		{
 			CreateDTE();
 			string fileName = @"d:\projects\myproject\myproject.sln";
-			fakeProjectService.OpenSolution.FileName = fileName;
+			SetOpenSolutionFileName(fileName);
 			
 			string fullName = dte.Solution.FullName;
 			
@@ -54,7 +65,7 @@ namespace PackageManagement.Tests.EnvDTE
 		{
 			CreateDTE();
 			string expectedFileName = @"d:\projects\myproject\myproject.sln";
-			fakeProjectService.OpenSolution.FileName = expectedFileName;
+			SetOpenSolutionFileName(expectedFileName);
 			
 			string fileName = dte.Solution.FileName;
 			
@@ -147,5 +158,29 @@ namespace PackageManagement.Tests.EnvDTE
 			
 			Assert.AreEqual("10.0", version);
 		}
+		
+		[Test]
+		public void Solution_SetGlobalsVariableValueAndThenAccessSolutionPropertyAgainAndGetSolutionGlobalsVariable_GlobalsVariableValueReturned()
+		{
+			CreateDTE();
+			
+			dte.Solution.Globals.set_VariableValue("test", "test-value");
+			object variableValue = dte.Solution.Globals.get_VariableValue("test");
+			
+			Assert.AreEqual("test-value", variableValue);
+		}
+		
+		[Test]
+		public void Solution_OpenSolutionChangesAfterSolutionPropertyAccessed_SolutionReturnedForCurrentOpenSolution()
+		{
+			CreateDTE();
+			SetOpenSolutionFileName(@"d:\projects\first\first.sln");
+			Solution firstSolution = dte.Solution;
+			
+			OpenSolution(@"d:\projects\second\second.sln");
+			
+			string fileName = dte.Solution.FileName;
+			Assert.AreEqual(@"d:\projects\second\second.sln", fileName);
+		}
 	}
 }