setting values of the model from a model

Question

I have 3 models

1st Model

public class BlogPosts
    {
        public int BlogID { get; set; }
        public int UserID { get; set; }
        public string PostTitle { get; set; }
        [AllowHtml]
        public string BlongContent { get; set; }
}

2nd Model

public class User
{
    public int User_ID { get; set; }
    public string User_Name { get; set; }
    public string User_Email { get; set; }
    public string Password { get; set; }
    public DateTime Registar_Date { get; set; }
}

and here is 3rd model which suppose to do a job of getting and seting values of other two models but it return null reference exception whenever i try to set the values.

 public class getModels
    {
        public BlogPosts post { get; set; }         
        public User user { get; set; }        

    }

Sample Controler code

 public ActionResult Index()
        {
            var m = new getModels();
            m.post.PostTitle = "Titlee of the post";
            ViewBag.tit = m.post.PostTitle;            
            return View();
        }

Any kind of Help or guidance please

Answer 1

You can do the same using auto properties:

public class BlogPosts
{
    public int BlogID { get; set; }
    public int UserID { get; set; }
    public string PostTitle { get; set; }
    [AllowHtml]
    public string BlongContent { get; set; }
}

public class User
{
    public int User_ID { get; set; }
    public string User_Name { get; set; }
    public string User_Email { get; set; }
    public string Password { get; set; }
    public DateTime Registar_Date { get; set; }
}

public class getModels
{
    public BlogPosts post { get; set; } = new BlogPosts();
    public User user { get; set; } = new User();
}

Answer 2

The BlogPosts and User object is null in the getModels class.

Either initialize those before setting any value or have codes in the constructor to pre-initialize the two objects:

public class getModels
{
     private BlogPosts _post;
     private User _user;
    
     public getModels()
     {
          this._post = new BlogPosts();
          this._user = new User();
     }
    
     public BlogPosts post { get{ return this._post; } set{ this._post = value; } }           
    
     public User user { get{ return this._user; } set{ this._user= value; } }
}

Or initialize the object before assigning the values in the action:

public ActionResult Index()
{
     var m = new getModels();
     m.post = new BlogPosts();
     m.post.PostTitle = "Titlee of the post";
     ViewBag.tit = m.post.PostTitle;            
     return View();
}

Answer 3

Your geModels properties are not initialized. you could just add a constructor:

public getModels() 
{
    post = new BlogPost();
    user = new User();
}

or initialize them in you contorller

public ActionResult Index()
{
    var m = new getModels();
    m.post = new BlogPost();
    m.post.PostTitle = "Titlee of the post";
    ViewBag.tit = m.post.PostTitle;            
    return View();
}