I am using the summernote plugin for text box: http://summernote.org/#/getting-started#basic-api
This is the form I have using summmernote:
Please, use [AllowHTML]
[AllowHTML]
There's a good article on MSDN Request Validation in ASP.NET
"To disable request validation for a specific property, mark the property definition with the AllowHtml attribute:"
[AllowHtml] public string Prop1 { get; set; }