Question

我有以下页面

public partial class GenericOfflineCommentary : OfflineFactsheetBase
{
}

其中OfflineFactsheetBase定义为

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具有以下virtual方法：

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

在所有影响OfflineFactsheetBase的页面中实现，如下所示：

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

目前，只有GenericOfflineCommentary的ExtractPageData（）被触发。如何将其修改为首先运行OfflineFactsheetBase的ExtractPageData（）然后再运行GenericOfflineCommentary？

编辑：我试图避免在每个实现者中调用base.ExtractPageData()。这可能吗？

Answer 1

使ExtractPageData方法非虚拟，并调用ExtractPageDataInternal虚拟方法：

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
}

派生类只会覆盖ExtractPageDataInternal，而不是ExtractPageData，因此基本实现将始终执行

Answer 2

澄清后修订

 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 ( );
        }
    }

    public void ExtractPageData ( )
    {
        // get stuff relevant to all pages that implement OfflineFactsheetBase 
        // ....blah...
        InternalExtractPageData ( );
    }
    // Could be abstract if the class where
    protected virtual void InternalExtractPageData ( )
    {
        // get stuff relevant to all pages that impmement OfflineFactsheetBase 
    }
}

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

OfflineFactsheetBase是抽象的吗？如果是这样，请将ExtractPageData保护为抽象，并从基础上的公共方法调用它，请参阅this SO question and answer

如何在实现者的方法之前执行基类的方法？

2 个答案: