System.IO.FileNotFoundException Could not load assembly System.Drawing

Hello,

I meet this error in a Xamarin.forms project using WebView and local html base url:

Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Perhaps it doesn't exist in the Mono for Android profile?
Nom de fichier : 'System.Drawing.dll'
à Xamarin.Android.Tuner.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters)
à Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences(ICollection`1 assemblies, AssemblyDefinition assembly, Boolean topLevel)
à Xamarin.Android.Tasks.ResolveAssemblies.Execute() Almicantarat.Droid

I read that: System.IO.FileNotFoundException: Could not load assembly System.Web in Mono for Android

but I don't know which client's source code I should compile.

I read that: Could not load file or assembly 'System.Drawing, Version=4.0.0.0
but in my project, reference to System.Drawing is coming from mono.android which is a Xamarin component!

Should I compile mono.android myself ? where could I find it ? does Xamarin provide it ?

See my references attached.

Thanks