I am trying to install the ArcGIS Runtime SDK for .NET using Visual Studio 2015 (I see that it is not supported yet for VS 2017, so I installed 2015). I downloaded and installed the Runtime SDK (100.30). I am not seeing any of the Esri/ArcGIS templates under projects so I opened an existing solution; an AddIn, and tried using nuGet to download the package. I got the following error: "Could not install package Esri.ArcGISRuntime 100.30. You are trying to install this package into a project that targets '.NETFramework, Version=v3.5' but the package does not contain any assembly references or content files that are compatible with that framework." What am I doing wrong here?
The issue is that your project targets .NET Framework v3.5. The current release of ArcGIS Runtime SDK for .NET requires minimum .NET Framework 4.6.1 (System requirements for 100.4.0—ArcGIS Runtime SDK for .NET | ArcGIS for Developers). You should update the target .NET Framework version to v4.6.1 or later (e.g. v4.7.2) and update the Esri.ArcGISRuntime.WPF NuGet reference to the current release of v100.4.
Regarding Visual Studio support - we provide templates via a Visual Studio Extension (.vsix) that supports Visual Studio 2017. You can still use Visual Studio 2015 and work with the NuGet packages directly.
OK, that makes sense (I think; I am totally new to this). By the way, do you know of any tutorials or documentation that show how to create an add on for ArcGIS Desktop (not Pro) using Visual Studio/ .NET? Everything out there on the ESRI sight is geared towards Pro.