C# add item in abstract list-CodePudding

For a project i am working with intherentance and an abstract class. with the help of a form i want to add items into a list, but get the following error during coding: cannot create an instance abstract type or interface 'Article'. does someone know how to fixt his?

articlemanager class:

 private List<Article> items;

        public ArticleManager()
        {
            items = new List<Article>();
        }
        public void addArticleEmergency(Article emergencyNews)
        {
            items.Add(emergencyNews);
        }

abstract article class:

  abstract class Article
    {
        public int id { get; private set; }
        public string title { get; private set; }
        public string text { get; private set; }

        public Article(int id, string title, string text)
        {
            this.id = id;
            this.title = title;
            this.text = text;
        }

        public bool HasID(int id)
        {
            if (id == this.id)
            {
                return true;
            }
            return false;
        }

        public override string ToString()
        {
            return id   ": \r\n"   title   " \r\n "   text;
        }
    }
}

form:

private ArticleManager articalManagerAdd;

        public Form1()
        {
            InitializeComponent();
            this.articalManagerAdd = new ArticleManager();
        }

      
        private void btnMakeNewsArticle_Click(object sender, EventArgs e)
        {
            if(txtNewsNumber.Text == "" || txtNewsTitle.Text == "" || txtNewsText.Text == "" || !rbEmergency.Checked && !rbNormal.Checked )
            {
                lbSeeNewsItem.Items.Clear();
                lbSeeNewsItem.Items.Add("Please fill in all the required information");
            }
            else
            {
                if (articalManagerAdd.GetArticle(Convert.ToInt32(txtNewsNumber.Text)) == null)
                {
                    if (rbNormal.Checked)
                    {
                        articalManagerAdd.addArticleNormal(new Article(Convert.ToInt32(txtNewsNumber.Text), txtNewsTitle.Text, txtNewsText.Text));
                        MessageBox.Show("Normal news article has been added");
                    }
                    else if(rbEmergency.Checked)
                    {
                        Article emergencyNews = new NewsArticle(Convert.ToInt32(txtNewsNumber.Text), txtNewsTitle.Text, txtNewsText.Text);
                        MessageBox.Show("Emergency news article has been added");
                    }
                }
                else
                {
                    lbSeeNewsItem.Items.Add("This id has already been used");
                }
            }
            
        }

CodePudding user response：

As the comments have mentioned, you cannot create an instance of an abstract class.

So your code new Article(Convert.ToInt32(txtNewsNumber.Text), txtNewsTitle.Text, txtNewsText.Text)) will not compile.

You can inherit from a non-abstract class so your NewsArticle class would be expected to work if you just removed the abstract modifier to your Article class.

Alternatively you could add a new sub-class of Article say NormalArticle and use that in your addArticleNormal method