Insert new entity to context with identity primary key

I want to insert a new record into my SQL table. I tried:

        public void CreateComment(int questionId, string comment)
        {
            QuestionComment questionComment = context.TableName.Create();//1*
            questionComment.propertyThatIsNotAConstraint= questionId;
            questionComment.body = comment;
            context.QuestionComments.Add(questionComment);
            context.SaveChanges();//ERROR...
        }

1* I'm surprised to see intellisense tell me: "Note that the new entity is not added or attached to the set"

Error Reads:

"Violation of PRIMARY KEY constraint 'PK_TableName'. Cannot insert duplicate key in object 'dbo.TableName'. The duplicate key value is (0).\r\nThe statement has been terminated."

The problem is that questionComment has its PK: questionComment.Id defaulted to 0. It needs to be the next available Identity or otherwise not populated and do a "normal" identity insert.

How does entity framework expect me to handle this scenerio?

As Requested:

//------------------------------------------------------------------------------
// <auto-generated>
//    This code was generated from a template.
//
//    Manual changes to this file may cause unexpected behavior in your application.
//    Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

    namespace Feedback.Models
    {
        using System;
        using System.Collections.Generic;

        public partial class QuestionComment
        {
            public int id { get; set; }
            public int questionId { get; set; }
            public string body { get; set; }
            public int commentIndex { get; set; }
        }
    }