Why should we do this?

There will be some requirements in most of our projects that has to repeat same operations on every page. This will make us to repeat the same code in every page and thus making it redundant. Here comes the use of introducing our own custom BasePage class in the codebehind class inheritance hierarchy. By including a custom BasePage class we can put all the repetitive operation in the BasePage and hence we can reuse it on every page. This article will help you to understand the implementation custom BasePage class in a simpler way with some example scenarios. 

How to achieve this?

Include a class called BasePage that derives System.Web.UI.Page class as shown in the below code.

BasePage Class

public class BasePage : System.Web.UI.Page

{

protected override void OnLoad(EventArgs e)

    {

       base.OnLoad(e);

     }

 }

Now, make the codebehind classes to inherit our custom BasePage class.

CodeBehind Class

public partial class Register : BasePage

{

}

Moving forward we will see some of the common scenarios where we can use the BasePage class.

Custom Error Handling

One way of handling the errors in ASP.Net page is using the Page_Error Event. This event can be used to seize the error that is occurring in page level. i.e. including a Page_Error event in codebehind class will make the ASP.Net to call the event whenever any error occurred on the page.

void Page_Error(object sender, EventArgs e)

    {

//Log to EventLog or Sql Error log table     

 Server.Transfer("Error.aspx");      

    }

In this scenario, we can use the BasePage and declare the event in the BasePage class and thus we can prevent the redundant code in every codebehind class. Our BasePage class will now look like,

public class BasePage : System.Web.UI.Page

{   

        protected override void OnLoad(EventArgs e)

        {

            base.OnLoad(e);

        }

    void Page_Error(object sender, EventArgs e)

    {

       Server.Transfer("Error.aspx");      

    }

}

If you need to log or display a detailed technical error information on the error page then make sure you are using Server.Transfer() instead of Response.Redirect() because only then you can use Server.GetLastError() method to get the error information on the error page. It is because Response.Redirect() will make redirection to Error.aspx as a new request and hence it will not have error information that is occurred on the page which will be actually previous request in this scenario.

Making Meta Tags with BasePage

With the introduction ASP.Net 2.0 we can set the Meta tag from the codebehind file using HtmlMeta class. Instead of repeating the code that adds the Meta tag on every page we can move this part to BasePage class. A very good approach will be a exposing a public property in BasePage and setting the Meta tag from the @Page directive.

Our BasePage will be,

public class BasePage : System.Web.UI.Page

{

    private string _metakeywords;

    private string _metadescription;

    public string MetaKeywords

    {

        get

        {

            return _metakeywords;

        }

        set

        {

            _metakeywords = value;

        }

    }

    public string MetaDescription

    {

        get

        {

            return _metadescription;

        }

        set

        {

            _metadescription = value;

        }

    }

     protected override void OnLoad(EventArgs e)

        {

            if (!String.IsNullOrEmpty(MetaKeywords))

            {

                HtmlMeta tag = new HtmlMeta();

                tag.Name = "keywords";

                tag.Content = MetaKeywords;

                Header.Controls.Add(tag);

            }

            if (!String.IsNullOrEmpty(MetaDescription))

            {

                HtmlMeta tag = new HtmlMeta();

                tag.Name = "description";

                tag.Content = MetaDescription;

                Header.Controls.Add(tag);

            }

            base.OnLoad(e);

        } 

}

To make this work we need to include CodeFileBaseClass="BasePage" attribute in @Page directive in the ASPX. This is done because in visual studio the codebehind file is referenced through CodeFile attribute which has the path of the code and this attribute is used to specify the actual class name. Now we can specify the Meta keywords and descriptions in @Page directive like,

<%@ Page Language="C#" AutoEventWireup="true" CodeFileBaseClass="BasePage" CodeFile="Default.aspx.cs" MetaKeywords="ASP.Net,CSharp" MetaDescription="BasePage implementation in ASP.Net" Inherits="_Default" %>

This will add Meta tags to every page when it is rendered. Besides this you can also declare some constants that you require on every page of your projects.