Fix exception when NuGetPSVariables package iterates over project properties.

src/AddIns/Misc/PackageManagement/Project/PackageManagement.csproj

@@ -36,6 +36,7 @@
     <DefineConstants>TRACE</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="Microsoft.Build" />
     <Reference Include="NuGet.Core">
       <HintPath>..\RequiredLibraries\NuGet.Core.dll</HintPath>
     </Reference>

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

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.IO;
 
 using ICSharpCode.SharpDevelop.Project;
+using Microsoft.Build.Construction;
 using SD = ICSharpCode.SharpDevelop.Project;
 
 namespace ICSharpCode.PackageManagement.EnvDTE
@@ -142,5 +143,16 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 			fileProjectItem.Include = include;
 			return fileProjectItem;
 		}
+		
+		internal IList<string> GetAllPropertyNames()
+		{
+			var names = new List<string>();
+			lock (MSBuildProject.SyncRoot) {
+				foreach (ProjectPropertyElement propertyElement in MSBuildProject.MSBuildProjectFile.Properties) {
+					names.Add(propertyElement.Name);
+				}
+			}
+			return names;
+		}
 	}
 }

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

@@ -3,6 +3,8 @@
 
 using System;
 using System.Collections.Generic;
+using ICSharpCode.SharpDevelop.Project;
+using Microsoft.Build.Construction;
 
 namespace ICSharpCode.PackageManagement.EnvDTE
 {
@@ -22,7 +24,9 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 		
 		public IEnumerator<Property> GetEnumerator()
 		{
-			throw new NotImplementedException();
+			foreach (string propertyName in project.GetAllPropertyNames()) {
+				yield return CreateProperty(propertyName);
+			}
 		}
 	}
 }

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

@@ -2,6 +2,7 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using System.Linq;
 using ICSharpCode.PackageManagement.EnvDTE;
 using NUnit.Framework;
 using PackageManagement.Tests.Helpers;
@@ -113,5 +114,17 @@ namespace PackageManagement.Tests.EnvDTE
 			
 			Assert.AreEqual(expectedTargetFrameworkMoniker, targetFrameworkMoniker);
 		}
+		
+		[Test]
+		public void GetEnumerator_TargetFrameworkVersionSetTo40_TargetFrameworkVersionPropertyReturned()
+		{
+			CreateProperties();
+			msbuildProject.SetProperty("TargetFrameworkVersion", "4.0");
+			
+			Property targetFrameworkVersionProperty = project.Properties.First(p => p.Name == "TargetFrameworkVersion");
+			string targetFrameworkVersion = targetFrameworkVersionProperty.Value as string;
+			
+			Assert.AreEqual("4.0", targetFrameworkVersion);
+		}
 	}
 }