Adding the Visual Studio Design time targets to the SDK (#860)

sdk/Sdk/Targets/Microsoft.Azure.Functions.Worker.Sdk.targets

@@ -30,6 +30,7 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
     <_FunctionsExtensionsJsonName>extensions.json</_FunctionsExtensionsJsonName>
     <_FunctionsExtensionsFullPublish Condition="$(NoBuild) == '' And $(_FunctionsExtensionsFullPublish) == ''">True</_FunctionsExtensionsFullPublish>
     <_FunctionsExtensionsFullPublish Condition="$(_FunctionsExtensionsFullPublish) == ''">!$(NoBuild)</_FunctionsExtensionsFullPublish>
+    <MSBuildFunctionsTargetsPath>$(MSBuildExtensionsPath)\Microsoft\VisualStudio\Managed.Functions\</MSBuildFunctionsTargetsPath>
   </PropertyGroup>
 
   <UsingTask TaskName="GenerateFunctionMetadata"
@@ -41,6 +42,9 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
   <UsingTask TaskName="ZipDeployTask"
             AssemblyFile="$(_FunctionsTaskAssemblyFullPath)"/>
 
+  <Import Project="$(MSBuildFunctionsTargetsPath)Microsoft.Azure.Functions.Designtime.targets" 
+         Condition="Exists('$(MSBuildFunctionsTargetsPath)Microsoft.Azure.Functions.Designtime.targets')" />
+
   <Target Name="_FunctionsPreBuild" BeforeTargets="BeforeBuild">
       <Message Condition="'$(_AzureFunctionsNotSet)' == 'true'" Importance="high" Text="AzureFunctionsVersion not configured in the project. Setting AzureFunctionsVersion to v3"/>
       <Error Condition="$(AzureFunctionsVersion.StartsWith('v1',StringComparison.OrdinalIgnoreCase))" Text="AzureFunctionsVersion is set to an incompatible version, Please set it to v4"/>