Can not assign property of nested model using LINQ

Question

I have a model which has inside another model as:

  public class DesignListViewModel
    {
        public IList<DesignViewModel> DesignList { get; set; } = new List<DesignViewModel>();
    }

So I want to assign a property inside that DesignViewModel in my controller using LINQ as:

  var rModel = await _designService.Get(model); //rModel equals to DesignListViewModel

  //Trying to assign column duedate 
  rModel.DesignList.Select(design => design.DueDate).FirstOrDefault() = new DateTime();

But it throws an error:

The left-hand side of an assignment must be a variable, property or indexer

How can I access that column as a variable to assign the new value?

Answer 1

If you need to assign property/field of some class instance (assuming DesignViewModel is a class) you need to aquire the instance and specify what you are trying to set. For example:

rModel.DesignList.First().DueDate = new DateTime();

Or via variable:

var first = rModel.DesignList.First();
first.DueDate = new DateTime();

Note that FirstOrDefault in this case does not make much sense cause for empty list it will result in null with following code producing NullReferenceException.