Question

Lets imaging the we have model:

public class InheritModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public string OtherData { get; set; }
}

We have a controller with View, that represents this model:

private InheritModel GetAll()
{
    return new InheritModel
    {
        Name = "name1",
        Description = "decs 1",
        OtherData = "other"
    };
}

public ActionResult Index()
{
    return View(GetAll());
}

Now we can edit this in View, change some data and post in back to server:

[HttpPost]
public ActionResult Index(InheritModel model)
{
    var merged = new MergeModel();
    return View(merged.Merge(model, GetAll()));
}

What i need to do:

• In view we have a reproduction of model
• User change something and post
• Merge method need to compare field-by-field posted model and previous model
• Merge method create a new InheritModel with data that was changed in posted model, all other data should be null

Can somebody help me to make this Merge method?

UPDATE(!)

It’s not a trivial task. Approaching like:

public InheritModel Merge(InheritModel current, InheritModel orig)
{
    var result = new InheritModel();
    if (current.Id != orig.Id) 
    {
        result.Id = current.Id;
    }
}

Not applicable. It’s should be Generic solution. We have more than 200 properties in the model. And the first model is built from severeal tables from DB.

Answer 1

public InheritModel Merge(InheritModel current, InheritModel orig)
{
    var result = new InheritModel();
    if (current.Id != orig.Id) 
    {
        result.Id = current.Id;
    }
    if (current.Name != orig.Name) 
    {
        result.Name = current.Name;
    }
    ... for the other properties

    return result;
}

Another possibility is to use reflection and loop through all properties and set their values:

public InheritModel Merge(InheritModel current, InheritModel orig)
{
    var result = new InheritModel();
    var properties = TypeDescriptor.GetProperties(typeof(InheritModel));
    foreach (PropertyDescriptor property in properties)
    {
        var currentValue = property.GetValue(current);
        if (currentValue != property.GetValue(orig))
        {
            property.SetValue(result, currentValue);
        }
    }
    return result;
}

Obviously this works only for 1 level nesting of properties.