Question

I have the following page

public partial class GenericOfflineCommentary : OfflineFactsheetBase
{
}

where OfflineFactsheetBase is defined as

public class OfflineFactsheetBase : System.Web.UI.Page
{
    public OfflineFactsheetBase()
    {
        this.Load += new EventHandler(this.Page_Load);
        this.PreInit += new EventHandler(this.Page_PreInit);
    }

    protected void Page_PreInit(object sender, EventArgs e)
    {
        if (Request.QueryString["data"] != null)
        {
            this.PageData = StringCompressor.DecompressString(Request.QueryString["data"]);
            this.ExtractPageData();
        }
    }
}

OfflineFactsheetBase has the following virtual method:

public virtual void ExtractPageData()
{
    // get stuff relevant to all pages that impmement OfflineFactsheetBase 
}

which is implemented in all pages that impmement OfflineFactsheetBase as follows:

public partial class GenericOfflineCommentary : OfflineFactsheetBase
{
    public override void ExtractPageData()
    {
            // get stuff relevant to an OfflineCommentary page.
    }
}

Currently, only GenericOfflineCommentary‘s ExtractPageData() is firing. How can I modify this to first run OfflineFactsheetBase‘s ExtractPageData() and then GenericOfflineCommentary‘s?

edit: I’m trying to avoid having to call base.ExtractPageData() in every implementor. Is this possible?

Answer 1

Make the ExtractPageData method non-virtual, and call a ExtractPageDataInternal virtual method :

public void ExtractPageData()
{
    // get stuff relevant to all pages that impmement OfflineFactsheetBase

    // base implementation
    ...

    // call derived class implementation
    this.ExtractPageDataInternal();
}

protected virtual void ExtractPageDataInternal()
{
    // implementation to be defined by derived class
}

The derived class will only override ExtractPageDataInternal, not ExtractPageData, so the base implementation will always be executed