ResXResourceWriter in Xamarin.Forms targeting .netstandard 2.0

Hello,

I'm trying to add resources to a resx file but Visual Studio doesn't find ResXResourceWriter and complains:

''' The type or namespace name does not exist in the namespace 'System.Resources' (are you missing an assembly reference?)

using (ResXResourceWriter resx = new ResXResourceWriter(@.\AppResources.resx))
{
resx.AddResource("Test", "Test123");
}

I'm using a .NetStandard 2.0 Xamarin Forms Project.

Thanks for your attention. I’m looking forward