如何使用实例化的 object 从一种方法到另一种方法？

Question

I have these two methods:

 public MessagesPage(ContactModel input)
        {
            InitializeComponent();
            NavigationPage.SetHasNavigationBar(this, false);
            ConversationsList = new ObservableCollection<ConversationModel>();
            ContactModel ConversationPartner = new ContactModel();
            ConversationPartner = input;
            ...
        }

And the input which is the parameter in the method above, I also would like to use it in this method (they're in the same class)

 private async void Send()
        {
            Guid guid = Guid.NewGuid();
            string ID = guid.ToString();
            ConversationModel conversationObject = new ConversationModel()
            {
                id = ID,
                converseeID = dataClass.loggedInUser.uid,
                message = Message,
                created_at = DateTime.UtcNow
            };
            await CrossCloudFirestore.Current
                    .Instance
                    .GetCollection("contacts")
                    .GetDocument(ConversationPartner.id)
                    .GetCollection("conversations")
                    .GetDocument(ID)
                    .SetDataAsync(conversationObject);
            Message = string.Empty;
        }

because as you can see, in.GetDocument, it needs the id of ConversationPartner. I would get object reference not set to an instance of an object when the Send() method is called because it doesn't have access to ContactModel input in MessagesPage above.

Answer 1

you need to declare ConversationPartner as a class level variable, not inside of of a specific method. This will make it available throughout your class

ContactModel ConversationPartner;

public MessagesPage(ContactModel input)
{
   InitializeComponent();
   NavigationPage.SetHasNavigationBar(this, false);
   ConversationsList = new ObservableCollection<ConversationModel>();
       
   ConversationPartner = input;
   ...
}