CKEditor Image Upload
Here is a tutorial on how to upload image with ASP:NET MVC2 (not Webforms) using CKEditor
http://arturito.net/2010/11/03/file-and-image-upload-with-asp-net-mvc2-with-ckeditor-wysiwyg-rich-text-editor/
Here is a image uploader I originally wrote in ASP.NET WebForms for Fckeditor (hence the theme no longer matches), that I've modified to work with Ckeditor.
https://github.com/mcm-ham/ckeditor-image-uploader
Update: I've now added an example showing how you can add this WebForms image uploader to a MVC project.
Update 2: I've now added a Razor Pages version which can be used in .NET Core MVC projects.