C＃-将不同类型作为一个参数传递

Question

I used Extract Method on this code because there were multiples of this code, and here is what it became:

private void InsertStatement(string table, string table2, TestURLGUI4.Form1 form, SQLiteConnection sql_con, ref int dbID, ref int dbID2, Chrome chrome, int max)
{
    try
    {
        List<int> dbIDs = new List<int>();
        using (SQLiteTransaction mytransaction = sql_con.BeginTransaction())
        {
            using (SQLiteCommand mycommand = new SQLiteCommand(sql_con))
            {
                mycommand.CommandText = "insert or ignore into " + table + " (id, url, title, visit_count, frecency, last_visit_date) values (@dbID,@url,@title,@visit,@frecency,@time)";

                for (var count2 = 0; count2 < chrome.URLs.Count; count2++)
                {
                    URL u = chrome.URLs[count2];
                    mycommand.Parameters.Add(new SQLiteParameter("@dbID", dbID));
                    mycommand.Parameters.Add(new SQLiteParameter("@url", u.url));
                    mycommand.Parameters.Add(new SQLiteParameter("@title", u.title));
                    mycommand.Parameters.Add(new SQLiteParameter("@visit", u.frequency));
                    mycommand.Parameters.Add(new SQLiteParameter("@time", ToPRTime(u.visited)));
                    mycommand.Parameters.Add(new SQLiteParameter("@frecency", ToFrecency(u.frequency)));
                    mycommand.ExecuteNonQuery();
                    dbIDs.Add(dbID);
                    dbID++;
                    form.label1.Text = count2 + "/" + max;
                    Application.DoEvents();
                }

            }
            mytransaction.Commit();
        }
        using (SQLiteTransaction mytransaction = sql_con.BeginTransaction())
        {
            using (SQLiteCommand mycommand = new SQLiteCommand(sql_con))
            {
                mycommand.CommandText = "insert or ignore into " + table2 + " (id, from_visit, place_id, visit_date, visit_type, session) values (@dbID2,2,@dbID,@time,1, 0)";

                for (var count2 = 0; count2 < chrome.URLs.Count; count2++)
                {
                    URL u = chrome.URLs[count2];
                    mycommand.Parameters.Add(new SQLiteParameter("@dbID2", dbID2));
                    mycommand.Parameters.Add(new SQLiteParameter("@dbID", dbIDs[count2]));
                    mycommand.Parameters.Add(new SQLiteParameter("@time", ToPRTime(u.visited)));
                    mycommand.ExecuteNonQuery();
                    dbID2++;
                    form.label1.Text = count2 + "/" + max;
                    Application.DoEvents();
                }

            }
            mytransaction.Commit();
        }
    }
    catch
    {
        throw;
    }
}

The only problem is, instead of the Chrome type parameter, I have created multiple instances of different classes, and I need to pass each one, for example, I have

IE ie = new IE();
Firefox firefox = new Firefox();

etc. Now, how can I modify my parameter so that instead of Chrome, I can pass Chrome, Firefox, IE, etc. all in the same parameter, one at a time?

Answer 1

Have the different browsers inherit from a base Browser class (or implement a common interface) and pass that in.

public abstract class Browser
{
    public List<URL> URL { get; private set; }

    protected Browser
    {
        URL = new List<URL>();
    }

    public abstract void NavigateTo(URL url);
}

Then implement the browsers and their specific functionality as needed:

public class InternetExplorer : Browser
{
    private Random rand = new Random();
    public override void NavigateTo(URL url)
    {
        if (rand.NextDouble() < 0.5)
            throw new InvalidOperationException();
        else
            url.Navigate();
    }   
}

public class Firefox : Browser
{
    public override void NavigateTo(URL url)
    {
        Thread.Sleep(250);
        url.Navigate();
    }
}

public class Chrome : Browser
{
    public override void NavigateTo(URL url)
    {
        url.Navigate();
        GoFaster();
    }
}

Rewrite your method to take the Browser and promote whatever shared properties are necessary to that base class:

private void InsertStatement(string table, string table2, TestURLGUI4.Form1 form, SQLiteConnection sql_con, ref int dbID, ref int dbID2, Browser browser, int max)

Answer 2

Your best bet is to create a common interface type that the browser classes can implement (something like IBrowser ). Then your method signature becomes:

private void InsertStatement(string table, string table2, TestURLGUI4.Form1 form, SQLiteConnection sql_con, ref int dbID, ref int dbID2, IBrowser browser, int max)

And within the method you'll have to add some conditional logic to figure out which type it is:

if(browser is Firefox)
{
...
}

Of course, if the browser types all do the same thing, you should probably just have one Browser class that has some sort of UserAgent field to identify it. Then you really don't need the conditional.

Answer 3

All your types are browsers, which means that you can (and should) refactor your code so that they all derive from one shared Browser class, if it's not already like this. Once you do this, you can polymorphically change your method:

private void InsertStatement(string table, string table2, TestURLGUI4.Form1 form, SQLiteConnection sql_con, ref int dbID, ref int dbID2, Browser browser, int max)

If you are unwilling to do this then the only other solution I can think of is overloading the method.

This article supplies information about inheritance in C#. Basically, what you do is:

class Browser
{
}

class IE : Browser
{
}

You can then still initialize IE like this:

IE ie = new IE();

But you can also initialize it polymorphically like this:

 Browser ie = new IE();

If you derive more classes from Browser, such as Firefox, Chrome, etc. then you can treat them all as a single type, Browser, inside a method.

Answer 4

Have them all implement an interface:

interface Browser
{

}

class Firefox : Browser
{

}
class IE : Browser
{

}

Browser ie = new IE();
//...
public void someMethod(Browser b)
//...