如何将对象null设置为viewmodel mvc c＃

Question

我有数据如果我linq查询该数据将获取数据或为null，并设置为viewmodel。 如果数据为null或没有数据，则mvc得到错误“对象引用未设置为对象的实例”]

我在linq查询时的代码

 var dpas = (from d in db.komputer
                        join b in db.vga on  d.komputerid equals (long?)b.komputerid
                        where d.komputername == id
                        select new detail_t_komputer
                        {
                            komputer = d.komputer,
                            komputername= d.komputername,
                            vga= d.vga,

                        }).DefaultIfEmpty(); 

我的视图模型

 var ViewModel = new KomputerVM
            {
                detail_t_komputer= dpas
            };

public class KomputerVM
    {
        public IQueryable<detail_t_komputer> detail_t_komputer{ get; set; }

    }

我的数据库使用MS Sql并使用mvc 5.2.7]

Answer 1

为什么要在KomputerVM类中使用IQueryable？

class Program
    {
        static void Main(string[] args)
        {
            List<myBigClass> myList = new List<myBigClass>
            {
                new myBigClass() {name = "Pippo", surname = "Poppo"},
                new myBigClass() { name = "Pluto", surname = "Ploto"}

            };

            var dpas = (from d in myList
                        where d.surname == "Ploto"
                        select new myfindclass
                        {
                            name = d.name,
                            myflag = true
                        }).DefaultIfEmpty();

            var ViewModel = new myClass
            {
                myvar = dpas
            };

        }

        public class myClass
        {
            public IEnumerable<myfindclass> myvar;

        }

    }

    public class myfindclass
    {
        public string name { get; set; }
        public bool myflag { get; set; }
    }

    public class myBigClass
    {
        public string name { get; set; }
        public string surname { get; set; }
    }