<Project DefaultTargets="Build"
 xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

    <!-- Change the target framework to 4.5 if using the ".NET 4.5" configuration -->
    <PropertyGroup Condition=" '$(Platform)' == '.NET 4.5' ">
        <DefineConstants Condition="'$(DefineConstants)'==''">
            TARGETTING_FX_4_5
        </DefineConstants>
        <DefineConstants Condition="'$(DefineConstants)'!='' and '$(DefineConstants)'!='TARGETTING_FX_4_5'">
            $(DefineConstants);TARGETTING_FX_4_5
        </DefineConstants>
        <PlatformTarget Condition="'$(PlatformTarget)'!=''"/>
        <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
    </PropertyGroup>

    <!-- Import the standard C# targets -->
    <Import Project="$(MSBuildBinPath)Microsoft.CSharp.targets" />

    <!-- Add .NET 4.5 as an available platform -->
    <PropertyGroup>
       <AvailablePlatforms>$(AvailablePlatforms),.NET 4.5</AvailablePlatforms>
    </PropertyGroup>
</Project>

<!-- Old Import Entry -->
<!-- <Import Project="$(MSBuildBinPath)Microsoft.CSharp.targets" /> -->

<!-- New Import Entry -->
<Import Project="Compile_4_5_CSharp.targets" />

<!-- Old default platform entry -->
<!-- <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform> -->

<!-- New default platform entry -->
<Platform Condition=" '$(Platform)' == '' ">.NET 4.5</Platform>

<PropertyGroup Condition="'$(Platform)' == 'AnyCPU'">
    <PlatformTarget>AnyCPU</PlatformTarget>
</PropertyGroup>

.
.
.
<ItemGroup>
.
.
.

using System;
using System.Text;

namespace testing
{
    using net45check = System.Reflection.ReflectionContext;
}

Error 6: The type or namespace name 'ReflectionContext' does not exist in
the namespace 'System.Reflection' (are you missing an assembly reference?)

<OutputPath>bin</OutputPath>

Property: REGISTRYVALUE1
RegKey: SoftwareMicrosoftNET Framework SetupNDPv4Full
Root: vsdrrHKLM
Value: Release

Condition: REGISTRYVALUE1>="#378389"
InstallUrl: http://www.microsoft.com/en-gb/download/details.aspx?id=30653
Message: Setup requires .NET Framework 4.5 to be installed.