How to optimize duplicated code between forms in C#

July 13, 2022

I have a self-made project called "Library Management", I have many forms: Book Form, Book Type Form, Author Form,…
But I realized that the code in the forms is very similar (only in some places like controls, ..).
How to reduce this duplication?. I know I have to create a base class and forms will inherit this class but I don’t know what to write in that base class.
Please help me, thank you very much

private void AuthorForm_Load(object sender, EventArgs e)
    {
        if (_authorDAL == null)
            _authorDAL = new AuthorDAL();

        loadData().ContinueWith((t) => 
        {
            if (InvokeRequired)
            {
                Invoke((MethodInvoker)(() =>
                {
                    bindingData();
                    applyUIStrings();
                }));
            }
            else
            {
                bindingData();
                applyUIStrings();
            }
        });
    }

And this is the duplicate code:

private void BookTypeForm_Load(object sender, EventArgs e)
    {
        if (bookTypeDAL == null)
            bookTypeDAL = new BookTypeDAL();

        loadData().ContinueWith((t) =>
        {
            if (InvokeRequired)
            {
                Invoke((MethodInvoker)(() =>
                {
                    bindingData();
                    applyUIStrings();
                }));
            }
            else
            {
                bindingData();
                applyUIStrings();
            }
        });
    }

>Solution :

There are a number of approaches you could take, but with inheritance, you could create an abstract base class with a method and use generics like this:

protected void Form_Load<T>(T dalObject)
    where T : new()
{
    if (dalObject == null)
        dalObject= new T();

    loadData().ContinueWith((t) =>
    {
        if (InvokeRequired)
        {
            Invoke((MethodInvoker)(() =>
            {
                bindingData();
                applyUIStrings();
            }));
        }
        else
        {
            bindingData();
            applyUIStrings();
        }
    });
}

which can then be called in the derived class:

private void AuthorForm_Load(object sender, EventArgs e)
{
    FormLoad<AuthorDAL>();
}

or simplified further to the call site like this:

form.Load += (s, e) => FormLoad<AuthorDAL>();

However, this would require your loadData, bindingData and applyUIStrings methods to be to visible in the base class too. If they’re different for each DAL type, you could make them virtual methods in the base class and override them in the derived classes.

Another approach, perhaps better, would be to have the common Form_Load in the base class, and have it call a virtual method to create the DAL object.

protected virtual void CreateDALObject();

protected void Form_Load(object sender, EventArgs e)
    where T : new()
{
    CreateDALObject();
    // ...
}

Or you could try to move methods out into supporting classes, which can be preferable to using inheritance, but sometimes difficult because WinForms so heavily rely on inheritance.