Could not install package 'NuGet.Client 3.2.0'

I'm working with RESTful webservice, getting error while adding package "System.Net.Http";

"The 'System.Net.Http 4.0.0' package requires NuGet client version '3.0' or above, but the current NuGet version is '2.8.5.0'. "

So, to resolve above error i'm trying to install "NuGet client" from "Add Package" option in xamarin studio, but this time I'm facing another issue that is;

"Could not install package 'NuGet.Client 3.2.0'. You are trying to install this package into a project that targets 'portable-net45+win+wp80+MonoAndroid10+xamarinios10+MonoTouch10', but the package does not contain any assembly references or content files that are compatible with that framework. For more information, contact the package author."

please help to resolve this issue.