Question

I have been learning C# for the past few days for use with ASP.NET to create websites.

I am very new to C# but I have been thinking about how I should go about writing my code to make it as reusable as possible.

As a quick example, lets say I wanted to create a piece of code to check a users login details which I could just drop into another site at any time, and have it work with the data it gets given.

Remembering that I have no idea how I should layout my code to do this, this is the idea I came up with (I will keep it short with some kind of pseudo code):

First I create a class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Module {
    public class Login {
        public static bool check_login(string usernameCheck = "", string passwordCheck = "") {
            if(usernameCheck == "user" && passwordCheck == "password") {
                return true;
            }

            return false;
        }
    }
}

Then I would have an aspx page where the login form would go, for example:

<asp:Content ContentPlaceHolderID="column1" runat="server">
    <asp:TextBox ID="usernameInput" runat="server"></asp:TextBox>
    <asp:TextBox ID="passwordInput" runat="server"></asp:TextBox>
    <asp:Button OnClick="check_login" Text="Login" runat="server" />
</asp:Content>

And the code behind file would look like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Module {
    public partial class _default : System.Web.UI.Page {
        protected void Page_Load(object sender, EventArgs e) {

        }

        protected void check_login(object sender, EventArgs e) {
            if(Login.check_login(usernameInput.Text, passwordInput.Text)) {
                Response.Redirect("some other place");
            }
        }
    }
}

This works as expected, but what I want to know is:

• Is there a better way to create reusable code?
• How do you design your reusable code?

I’m sure there must be a better way for me to do this, but I just can’t think of it on my own.

Answer 1

With regard to ASP.NET WebForms and reusability, it has to be said that the most common issue lies with putting too much logic into the code-behind files. Programmers, especially those new to ASP.NET WebForms, tend to put there parts of business logic and even database access code. After a while, it turns their application into a giant hard-to-maintain blurb.

Extract away your business logic into a separate layer. Access it from the code-behind. Just access, not implement it directly. Stay away from the database. Only the business layer should be allowed to talk to it.

You could even put your business logic and domain model entities into a separate class library. Then it’s how it becomes reusable.

That’s first simple considerations before you get your hands dirty with some serious coding.

Reusability techniques in .NET mostly revolve around shelving common code into class libraries to be used by a variety of applications.

Reusability as applied to web applications (ASP.NET) is usually achieved with UserControls (*.ascx) for the presentation part and exposing parts of the application via web services.

One could also mention moving the business logic into the database layer (putting it into stored procedures) but this one is commonly perceived as controversial these days.