base.csproj

<Project Sdk="MSBuild.Sdk.Extras/2.0.29">

  <PropertyGroup>
    <!--Update with your target such as: Xamarin.iOS10 or MonoAndroid80 or Xamarin.Mac20-->
    <TargetFramework>Xamarin.iOS10</TargetFramework>
    
    
    <!--To Multi-target you can do this-->
    <!--<TargetFrameworks>Xamarin.iOS10;MonoAndroid80</TargetFrameworks>-->
    
    <!--Assembly and Namespace info -->
    <AssemblyName>MyLibrary</AssemblyName>
    <RootNamespace>MyLibrary</RootNamespace>
    
    <Product>$(AssemblyName) ($(TargetFramework))</Product>
    <AssemblyVersion>1.0.0.0</AssemblyVersion>
    <AssemblyFileVersion>1.0.0.0</AssemblyFileVersion>
    <Version>1.0.0.0</Version>
    <NeutralLanguage>en</NeutralLanguage>
 
    
    <!--Don't auto add files for me, I will tell you -->
    <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
   
    <!-- Helper to add defines-->
    <DefineConstants>$(DefineConstants);</DefineConstants>    
    
    <!--Assembly and Namespace info -->
    
    <!--Version of C# to use -->
    <LangVersion>default</LangVersion>
    
  </PropertyGroup>
  
  <!-- Define what happens on build and release -->
   <PropertyGroup Condition=" '$(Configuration)'=='Debug' ">
    <DebugType>full</DebugType>
    <DebugSymbols>true</DebugSymbols>
    <GenerateDocumentationFile>false</GenerateDocumentationFile>
  </PropertyGroup>
  
  <PropertyGroup Condition=" '$(Configuration)'=='Release' ">
    <DebugType>pdbonly</DebugType>
    <GenerateDocumentationFile>true</GenerateDocumentationFile>
    
    <!-- If we want a nuget package add this
    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     -->
  </PropertyGroup>
  
  <ItemGroup>
    <!-- This None is here so the conditionally included files show up in the Solution Explorer -->
    <None Include="**\*.cs;**\*.xml;**\*.axml;**\*.png" Exclude="obj\**\*.*;bin\**\*.*;bin;obj" />
   
    <!-- We will compile anything ending in .shared.cs  You can change this --> 
    <Compile Include="**\*.shared.cs" />
  </ItemGroup>
  
  <ItemGroup Condition=" $(TargetFramework.StartsWith('MonoAndroid')) ">
    <Compile Include="**\*.android.cs" />
    <!-- if you have resources add this
    <AndroidResource Include="Resources\**\*.axml" />
    <AndroidResource Include="Resources\**\*.xml" />
    <AndroidResource Include="Resources\**\*.png" />
    -->
  </ItemGroup>

  <ItemGroup Condition=" $(TargetFramework.StartsWith('Xamarin.iOS')) ">
    <Compile Include="**\*.ios.cs" />
  </ItemGroup>
  
</Project>