Question

I have a project which i need to build in two different configurations. One configuration will target .net framework 3.5 and another will target .net framework 4.0.
First of all is that possible?
I have created a new configuration called DotNet35 (using the usual steps) which will target .net 3.5. I have done this by specifying the target version in the created project config as v3.5
It does not seem to work. Any idea why? Here is the property group section from my .csproj
(only manual addition is the TargetFrameworkVersion element)

<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'DotNet35|AnyCPU'">
    <DebugSymbols>true</DebugSymbols>
    <OutputPath>bin\DotNet35\</OutputPath>
    <DefineConstants>DEBUG;TRACE</DefineConstants>
    <DebugType>full</DebugType>
    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
    <PlatformTarget>AnyCPU</PlatformTarget>
    <CodeAnalysisLogFile>..\..\bin\Client\Debug\CS.XRAY.XRayClient.dll.CodeAnalysisLog.xml</CodeAnalysisLogFile>
    <CodeAnalysisUseTypeNameInSuppression>true</CodeAnalysisUseTypeNameInSuppression>
    <CodeAnalysisModuleSuppressionsFile>GlobalSuppressions.cs</CodeAnalysisModuleSuppressionsFile>
    <GenerateSerializationAssemblies>Off</GenerateSerializationAssemblies>
    <ErrorReport>prompt</ErrorReport>
    <CodeAnalysisRuleSet>AllRules.ruleset</CodeAnalysisRuleSet>
    <CodeAnalysisRuleSetDirectories>;C:\Program Files\Microsoft Visual Studio 10.0\Team Tools\Static Analysis Tools\\Rule Sets</CodeAnalysisRuleSetDirectories>
    <CodeAnalysisIgnoreBuiltInRuleSets>true</CodeAnalysisIgnoreBuiltInRuleSets>
    <CodeAnalysisRuleDirectories>;C:\Program Files\Microsoft Visual Studio 10.0\Team Tools\Static Analysis Tools\FxCop\\Rules</CodeAnalysisRuleDirectories>
    <CodeAnalysisIgnoreBuiltInRules>true</CodeAnalysisIgnoreBuiltInRules>
  </PropertyGroup>

Answer 1

I do not think you can do that with multiple configuration of the same project.

You can do that, though, by having multiple project files, each one targeting a different framework version.

EDIT: The easiest way to do that, btw is to just copy your current project file, open it, and change the targeted framework version.