I'm trying generics for the first time and am having a problem.
I have a dll that sends messages in batches
there is a "Message" class and a "Batch" class in that dll
on the batch class, I have some public properties
on of the batch class's public properties is a property called "Messages" which is a list of the "Message" class as follows:
public List<Message> Messages {get;set;}
Method 1
I then have a test exe where I want to set the properties on the "Batch" class as follows:
Batch myBatch = new Batch()
myBatch.Messages.Add(
new MyNameSpace.Message(txtToAddress.Text, txtMessage.Text));
When I run the app, I get:
"Object reference not set to an instance of an object."
Method 2
After playing around a bit, I see that I can successfully do the following in the test exe:
List<MyNameSpace.Message> myMessages = new List<MyNameSpace.Message>();
myBatch.Messages.Add(
new MyNameSpace.Message(txtToAddress.Text, txtMessage.Text));
myBatch.Messages = myMessages;
I'd like to get it working in the first way because other programmers will be using the dll and it seems more intutive to use the first approach.
What am I missing to get the first method to work?
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Normally, collections are initialized by the parent object:
public List<Message> Messages {get; private set;}
public Batch() { // constructor
Messages = new List<Message>();
}
Now it should work as expected. Note that if you are using XmlSerializer
you'll need to keep the public set too...
In some ways, the long-hand property code is easier here:
private List<Message> messages = new List<Message>();
public List<Message> Messages { get {return messages; } }
(no messing with constructors, etc)
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