Fix missing initializer for NullHandleRef (#3)

WpfScreenHelper.sln

@@ -1,9 +1,18 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 2013
-VisualStudioVersion = 12.0.30723.0
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.30204.135
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "WpfScreenHelper", "src\WpfScreenHelper\WpfScreenHelper.csproj", "{8346EB2E-BFBB-4D63-B974-352A4D8C07F1}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WpfScreenHelper", "src\WpfScreenHelper\WpfScreenHelper.csproj", "{8346EB2E-BFBB-4D63-B974-352A4D8C07F1}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{77B57BC9-49FD-4BB9-A303-611FFC5C12AF}"
+	ProjectSection(SolutionItems) = preProject
+		.gitattributes = .gitattributes
+		.gitignore = .gitignore
+		build.bat = build.bat
+		LICENSE = LICENSE
+		README.md = README.md
+	EndProjectSection
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -19,4 +28,7 @@ Global
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {BAF8370C-EA3E-4F99-A94C-FFC687353E0F}
+	EndGlobalSection
 EndGlobal

src/WpfScreenHelper/NativeMethods.cs

@@ -34,8 +34,8 @@ internal static class NativeMethods
         [DllImport(ExternDll.User32, ExactSpelling = true, CharSet = CharSet.Auto)]
         [ResourceExposure(ResourceScope.None)]
         public static extern bool GetCursorPos([In, Out] POINT pt);
-        
-        public static HandleRef NullHandleRef;
+
+        public static readonly HandleRef NullHandleRef = new HandleRef(null, IntPtr.Zero);
 
         public delegate bool MonitorEnumProc(IntPtr monitor, IntPtr hdc, IntPtr lprcMonitor, IntPtr lParam);
 

src/WpfScreenHelper/WpfScreenHelper.csproj

@@ -14,7 +14,7 @@
     <PackageTags>WPF Screen Monitor Display Helper</PackageTags>
     <RepositoryUrl>https://github.com/micdenny/WpfScreenHelper</RepositoryUrl>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
-    <Version>0.4.0</Version>
+    <Version>1.0.0</Version>
   </PropertyGroup>
 
   <Target Name="CopyPackage" AfterTargets="Pack">