CODEWITHSUNDEEP
c#classcollections
Raj
Raj

Reputation: 361

trying to Create user defined collection class with list<>

C# : I am trying to create collection class with list of some other user defined class but it show object not set to be an instance of an object when i trying to add object in main object. Here is my C# code :

namespace ConsoleApplication2
{

   public class Monthlst
    {
        public List<Monday> Monday { get; set; }
        public List<Tuesday> Tuesday { get; set; }
        public List<Wednesday> Wednesday { get; set; }
        public List<Thursday> Thursday { get; set; }
        public List<Friday> Friday { get; set; }
        public List<Saturday> Saturday { get; set; }
        public List<Sunday> Sunday { get; set; }

    }
   public class Monday
    {
        public int days { get; set; }
    }
   public class Tuesday
    {
        public int days { get; set; }
    }
   public class Wednesday
    {
        public int days { get; set; }
    }
   public class Thursday
    {
        public int days { get; set; }
    }
   public class Friday
    {
        public int days { get; set; }
    }
   public class Saturday
    {
        public int days { get; set; }
    }
   public class Sunday
    {
        public int days { get; set; }
    }
    class Program
    {


        static void Main(string[] args)
        {

          Monthlst objmonth = new Monthlst();
          Wednesday wednes = new Wednesday();
          wednes.days = 5;
          objmonth.Wednesday.Add(wednes); // here i am getting error object not set to.... 
        }
  }
}

Here i am just create instance of my Monthlst class in main method and the object of wednesday class in list property of Monthlst object but why it show me error i dont know Is there any wrong thing i am doing or not please explain....

Thanks, Raj

Upvotes: 1

Views: 1319

Answers (2)

Ria
Ria

Reputation: 10367

Init your Wednesday list item. Your code should be like this:

public class Monthlst
{
    public Monthlst()
    {
        Monday = new List<Monday>();
        Tuesday = new List<Tuesday>();
        Wednesday = new List<Wednesday>();
        Thursday = new List<Thursday>();
        Friday = new List<Friday>();
        Saturday = new List<Saturday>();
        Sunday = new List<Sunday>();
    }
    public List<Monday> Monday { get; set; }
    public List<Tuesday> Tuesday { get; set; }
    public List<Wednesday> Wednesday { get; set; }
    public List<Thursday> Thursday { get; set; }
    public List<Friday> Friday { get; set; }
    public List<Saturday> Saturday { get; set; }
    public List<Sunday> Sunday { get; set; }

}
public class Monday
{
    public int days { get; set; }
}
public class Tuesday
{
    public int days { get; set; }
}
public class Wednesday
{
    public int days { get; set; }
}
public class Thursday
{
    public int days { get; set; }
}
public class Friday
{
    public int days { get; set; }
}
public class Saturday
{
    public int days { get; set; }
}
public class Sunday
{
    public int days { get; set; }
}
class Program
{
    static void Main(string[] args)
    {
        var objmonth = new Monthlst();
        var wednes = new Wednesday {days = 5};
        objmonth.Wednesday.Add(wednes);
    }
}

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1499800

Yes, you're not initializing your properties. After construction, all of the Monthlst properties will be null. You need to create a list before adding to it. For example:

Monthlst objmonth = new Monthlst();
objmonth.Wednesday = new List<Wednesday>();
Wednesday wednes = new Wednesday();
wednes.days = 5;
objmonth.Wednesday.Add(wednes);

Alternatively, make the constructor for Monthlst initialize all its properties.

Aside from that, I think the design is somewhat ropy in various ways, but that's a different matter.

Upvotes: 2

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