Triangle.NET generates 2D (constrained) Delaunay triangulations and high-quality meshes of point sets or planar straight line graphs. The code is based on Jonathan Richard Shewchuk's Triangle project, see references below.
To get started, take a look at the wiki. There's also an extensive list of examples in the Triangle.Examples project (see overview in the wiki).
The original C code published by Jonathan Shewchuk comes with a proprietary license (see Triangle README) which, unfortunately, isn't very clear about how a derived work like Triangle.NET should be handled. Though Triangle.NET was published on Codeplex under the MIT license in 2012 (triangle.codeplex.com, no longer available), I recommend not using this code in a commercial context. This restriction only applies to the Triangle project and specifically those files containing a copyright header pointing to Jonathan Richard Shewchuk. The code contained in the other projects (like Triangle.Rendering or Triangle.Viewer) is released under MIT license.
Due to the unclear licensing situation, there will also be no Nuget package release. For further discussion, please refer to the open issue License Confusion.
If you want to learn about the algorithms used in Triangle.NET, I recommend taking a look at the following papers: