Question

I have two models that only differ by what fields are required, and I would like to be able to use the same view to display both of them.

I have a UserEdit class

public abstract class UserEdit
{
    public User User { get; set; }

    [DataType(DataType.Password)]
    [Display(Name = "Password")]
    public string NewPassword { get; set; }

    [DataType(DataType.Password)]
    [Display(Name = "Confirm password")]
    [EqualTo("NewPassword")]
    public string ConfirmPassword { get; set; }

}

and a UserCreate Class that adds the required attribute to the NewPassword and ConfirmPassword properties.

class UserCreate_Metadata
{
    [Required]
    public string NewPassword { get; set; }

    [Required]
    public string ConfirmPassword { get; set; }
}

[MetadataType(typeof(UserCreate_Metadata))]
public partial class UserCreate : UserEdit
{

}

Both of these work fine in the view if I bind the model to the specific class like so:

@model Siaa.NextWeb.Data.UserEdit

or

@model Siaa.NextWeb.Data.UserCreate

Is there a way to make the view detect which class it is binding to so that it picks up the extra validation requirement of the UserCreate class? I tried using a dynamic view, but receive a “expression tree may not contain a dynamic operation” which research has pointed me to the lambda expressions used to create the editors

@Html.EditorFor(model => model.User.FirstName)

Answer 1

The most intuitive way to do this would be to combine both models onto a single model that you always pass to the view. Then simply add some sort of flag on to the model that determines which one you should use.

public class UserViewModel {
    public UserCreate CreateModel { get; set; }
    public UserEdit EditModel { get; set; }

    public bool IsCreatingUser { get; set; }
}

Then in your view:

@if (Model.IsCreatingUser) {
    //Build your form.
} else {
    //Build your form.
}