Build as x64. Can't use Any CPU when we're going to use DllImport.

OpusSolver.sln

@@ -7,14 +7,14 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpusSolver", "OpusSolver\Op
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
-		Debug|Any CPU = Debug|Any CPU
-		Release|Any CPU = Release|Any CPU
+		Debug|x64 = Debug|x64
+		Release|x64 = Release|x64
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Release|Any CPU.Build.0 = Release|Any CPU
+		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Debug|x64.ActiveCfg = Debug|x64
+		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Debug|x64.Build.0 = Debug|x64
+		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Release|x64.ActiveCfg = Release|x64
+		{193959C5-6207-403E-8CD7-F2D3E12283F3}.Release|x64.Build.0 = Release|x64
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

OpusSolver/OpusSolver.csproj

@@ -13,8 +13,8 @@
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <TargetFrameworkProfile />
   </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
-    <PlatformTarget>AnyCPU</PlatformTarget>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
+    <PlatformTarget>x64</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
@@ -25,9 +25,10 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <RunCodeAnalysis>false</RunCodeAnalysis>
     <LangVersion>default</LangVersion>
+
   </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
-    <PlatformTarget>AnyCPU</PlatformTarget>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
+    <PlatformTarget>x64</PlatformTarget>
     <DebugType>pdbonly</DebugType>
     <Optimize>true</Optimize>
     <OutputPath>..\bin\Release\</OutputPath>