实现委托和事件会引发歧义错误
本文关键字:歧义 错误 事件 实现 | 更新日期: 2023-09-27 17:58:15
我在自定义控件lnkprev中添加了一个链接按钮。现在我已经创建了一个委托和一个事件。我想在点击lnkprev按钮时调用它。我这样做是为了防止关闭页面中调用自定义控件的部分。
public delegate void PagePrevHandler();
public event PagePrevHandler PagePrev;
protected void lnkprev_Click(object sender, EventArgs e)
{
PagePrev();
}
public void PagePrev()
{
List<ListItem> pages = new List<ListItem>();
int pageCount = TotalPages;
int lastnumber = FirstNumber - 10;
int nexttennumber = lastnumber + 10;
if (lastnumber >= 0)
{
if (lastnumber == 0)
{
lastnumber = 1;
nexttennumber = 11;
}
for (int i = lastnumber; i <= pageCount; i++)
{
if (i < nexttennumber && i > 0)
{
pages.Add(new ListItem(i.ToString(), i.ToString(), i != PageIndex));
}
}
FirstNumber = lastnumber;
LastNumber = nexttennumber;
rptPager.DataSource = pages;
rptPager.DataBind();
}
}
现在的问题是,它抛出了说错的歧义问题。"已包含'PagePreviv'的定义"
事实上,我并没有从网上获得代表和活动的概念。我从来没有实施过。
请帮帮我!!!
委托定义函数签名。它可以按原样用于定义回调函数的类型:
public class MyPageClass
{
public delegate void FirstPageCallback(string pageTitle);
// Method with a callback function
public void SomePageProcessing(FirstPageCallback fpcb, int pageNumber)
{
// Do some stuff
...
// Call the function defined in another class
fpcb("This is a title");
}
}
然后,可以在另一个类中声明具有适当签名的函数,并将其传递给MyPageClass对象的方法:
public class MyClientClass
{
private MyPageClass p = new MyPageClass();
private void ProcessPages()
{
// Pass DoFirstPageStuff as callback function
p.SomePageProcessing(DoFirstPageStuff, 7);
}
// This method has the signature specified by the FirstPageCallback delegate
// It will be called inside p.SomePageProcessing
private void DoFirstPageStuff(string title)
{
// Do something with the page title
...
}
}
EventHandler
委托通常用于声明事件。您可以使用自己的委托,但可能没有必要。
public class MyPageClass
{
public event EventHandler FirstPageLoaded;
public void MorePageProcessing(int pageNumber)
{
// Do some stuff
...
// Call all the registered event handlers
if (FirstPageLoaded != null)
{
FirstPageLoaded(this, EventArgs.Empty);
}
}
}
包含MyPageClass实例的类可以注册事件处理程序:
public class MyClientClass
{
private MyPageClass p = new MyPageClass();
private void ProcessMorePages()
{
// Register ProcessLoadedPage as event handler
p.FirstPageLoaded += ProcessLoadedPage;
}
// This method has the same signature as the EventHandler delegate
// It will be called inside p.MorePageProcessing
private void ProcessLoadedPage(object sender, EventArgs e)
{
...
}
}
EventHandler
委托有一个EventArgs
参数,该参数不包含任何数据。如果事件处理程序需要额外的数据,可以从EventArgs
:派生一个类
public class FirstPageEventArgs: EventArgs
{
public int PageNumber;
public string Title;
public FirstPageEventArgs(int pageNumber, string title)
{
PageNumber = pageNumber;
Title = title;
}
}
并将其与EventHandler
:的通用版本一起包含在事件声明中
public event EventHandler<FirstPageEventArgs> FirstPageLoaded;
事件处理程序将通过以下方式触发:
if (FirstPageLoaded != null)
{
FirstPageLoaded(this, new FirstPageEventArgs(currentPageNumber, "My title"));
}
并用适当的参数定义:
private void ProcessLoadedPage(object sender, FirstPageEventArgs e)
{
// Use the values of the derived EventArgs argument
int pageNumber = e.PageNumber;
string title = e.Title;
...
}
您有两个具有"PagePrevi"名称的元素-事件和方法。什么应该被称为,当你写:
PagePrev();
我认为,你应该重命名方法或事件,然后一切都应该正常工作