If / else语句ASP.NET C#
If / else语句ASP.NET C#
提问于 2012-01-27 04:44:11
到目前为止，我正在尝试创建一个ASP.NET页面，它将列出一个类别中的图书，在一个列表框中，根据你选择的类别按钮，然后我有另外两个按钮(一个用于下单和一个下单)。现在的问题是，当我点击虚构按钮并填充列表框后单击ASC或DESC按钮时，它会擦除列表框，并将我抛回pageload事件。
我曾尝试将填充项目移动到页面加载事件，当我完成所有操作时，一切都很完美，但由于某些原因，当通过其他按钮单击来执行此操作时，它就不起作用了。
我是ASP.NET的新手，所以非常欢迎简单的或者“新的友好”的解释和代码示例/修复！
提前感谢！
下面的代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class partin : System.Web.UI.Page
{
private List<String> books = new List<String>();
public void Page_PreRender()
{
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
}
int SortASC(string x, string y)
{
return String.Compare(x, y);
}
int SortDESC(string x, string y)
{
return String.Compare(x, y) * -1;
}
protected void Page_Load(object sender, EventArgs e)
{
Header_Label.Text = "Welcome! Please select a book category.";
}
protected void Fiction_Click(object sender, EventArgs e)
{
Header_Label.Text = "Fiction Section";
books.Add("Title: The Old Man and The Sea | Decription: An epic novel. | Price: 10 USD | Quantity: 3");
books.Add("Title: A Game of Thrones | Decription: A tale of fire and ice. | Price: 15 USD | Quantity: 6");
books.Add("Title: Dracula | Decription: A book about vampires. | Price: 5 USD | Quantity: 7");
books.Add("Title: Twilight | Decription: An awful book. | Price: Free | Quantity: 1000");
}
protected void Non_Fiction_Click(object sender, EventArgs e)
{
Header_Label.Text = "Non-Fiction Section";
}
protected void Self_Help_Click(object sender, EventArgs e)
{
Header_Label.Text = "Self Help Section";
}
protected void Sort_Command(object sender, CommandEventArgs e)
{
if (e.CommandName == "Sort")
{
switch (e.CommandArgument.ToString())
{
case "ASC":
books.Sort(SortASC);
break;
case "DESC":
books.Sort(SortDESC);
break;
}
}
}
}编辑:感谢你的帖子，它不再直接返回到页面加载事件，并将标签中的更改保留为“虚构”，但当我单击ASD或DESC按钮时，它仍会重置ListBox中的数据。
回答 3
Stack Overflow用户
回答已采纳
发布于 2012-01-27 04:48:03
您需要检查这是否是Page_Load中的回发：
if(!IsPostBack){
Header_Label.Text = "Welcome! Please select a book category";
//put your prerender logic in here, too...to populate the list of books.
}Page_Load每次都会触发。您通常将页面初始化逻辑放在那里，但对于回发(如单击按钮)，您不希望重新运行该初始代码。因此，检查页面是否处于回发状态(IsPostback==true)；如果不是，则初始化页面。否则，让页面在回发期间根据ViewState中存储的内容呈现。
Stack Overflow用户
发布于 2012-01-27 04:54:18
检查页面加载和排序命令修改事件
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class partin : System.Web.UI.Page
{
private List<String> books = new List<String>();
public void Page_PreRender()
{
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
}
int SortASC(string x, string y)
{
return String.Compare(x, y);
}
int SortDESC(string x, string y)
{
return String.Compare(x, y) * -1;
}
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack){
Header_Label.Text = "Welcome! Please select a book category.";
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
}
}
protected void Fiction_Click(object sender, EventArgs e)
{
Header_Label.Text = "Fiction Section";
books.Add("Title: The Old Man and The Sea | Decription: An epic novel. | Price: 10 USD | Quantity: 3");
books.Add("Title: A Game of Thrones | Decription: A tale of fire and ice. | Price: 15 USD | Quantity: 6");
books.Add("Title: Dracula | Decription: A book about vampires. | Price: 5 USD | Quantity: 7");
books.Add("Title: Twilight | Decription: An awful book. | Price: Free | Quantity: 1000");
}
protected void Non_Fiction_Click(object sender, EventArgs e)
{
Header_Label.Text = "Non-Fiction Section";
}
protected void Self_Help_Click(object sender, EventArgs e)
{
Header_Label.Text = "Self Help Section";
}
protected void Sort_Command(object sender, CommandEventArgs e)
{
if (e.CommandName == "Sort")
{
switch (e.CommandArgument.ToString())
{
case "ASC":
books.Sort(SortASC);
break;
case "DESC":
books.Sort(SortDESC);
break;
}
}
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
}
}Stack Overflow用户
发布于 2012-01-27 04:54:51
尝试将Page_PreRender中的代码放入Page_Load中
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Header_Label.Text = "Welcome! Please select a book category.";
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
}
}对于sort-metjhod添加数据绑定
protected void Sort_Command(object sender, CommandEventArgs e)
{
if (e.CommandName == "Sort")
{
switch (e.CommandArgument.ToString())
{
case "ASC":
books.Sort(SortASC);
break;
case "DESC":
books.Sort(SortDESC);
break;
}
}
Item_Listbox.DataSource = books;
Item_Listbox.DataBind();
} 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/9025055
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