CODEWITHSUNDEEP
c#.netentity-frameworkentity-framework-4.1
stephen776
stephen776

Reputation: 9234

Creating object with related objects in Entity Framework 4.1

I have the following database tables/EF objects

public class Transaction
{
    //some other properties
    public ICollection<TransactionItems> Items {get; set;}

}

public class TransactionItems
{
    //some properties
}

What I need to do is, create a new instance of transaction along with several instances of TransactionItems for its Items property and save all of these to my DB

I have tried the following:

Transaction trans = new Transaction();
//set its properties

Then in a foreach loop I am looping through a collection and creating a new TransactionItem for each member and attempting to add it to the trans object Item Collection

foreach(var item in myCollection)
{

     TransactionItem newItem = new TransactionItem();
     //set its properties

     //add it to the tran Item collection
    tran.TransactionItems.Add(newItem);//getting null reference here...

}

I am getting a null reference exception when I attempt to add a transactionITem to the Item collection of my Transaction object. What am I doing wrong?

Upvotes: 0

Views: 917

Answers (2)

Merlyn Morgan-Graham
Merlyn Morgan-Graham

Reputation: 59101

Did you ever Initialize TransactionItems in the constructor for Transaction or in your actual code?

public class Transaction
{
    public Transaction()
    {
        Items = new List<TransactionItems>();
    }

    //some other properties
    public ICollection<TransactionItems> Items {get; set;}
}

Or less preferrably (unless you also do the above):

Transaction trans = new Transaction()
{
    Items = myCollection.Select(
        item => new TransactionItem
        {
            // set its properties
        })
        .ToList();
};

Upvotes: 1

SLaks
SLaks

Reputation: 887215

You need to initialize the property to hold a collection instance in the constructor:

Items = new HashSet<TransactionItems>();

Upvotes: 2

Related Questions