If / else statement ASP.NET C#

本文关键字：NET ASP statement else If | 更新日期: 2023-09-27 18:21:47

目前，我正在尝试创建一个ASP.NET页面，该页面将根据您选择的类别按钮在列表框中列出某个类别中的书籍，然后我有另外两个按钮（一个用于DESC顺序，一个用于ASC顺序）。现在的问题是，当我在点击虚构按钮并填充列表框后点击ASC或DESC按钮时，它会擦除列表框，并将我带回页面加载事件。

我尝试过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，但由于某种原因，当通过其他按钮点击时，它根本不起作用。

我对ASP.NET很陌生，所以非常欢迎简单或"新手友好"的解释和代码示例/修复！

提前感谢！

下方的代码

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：感谢您的帖子，它不再直接返回页面加载事件，并将标签中的更改保留为"虚构"，但当我单击ASD或DESC按钮时，它仍在重新设置列表框中的数据。

If / else statement ASP.NET C#

您需要检查Page_Load:中是否存在回发

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（如按钮单击），您不希望重新运行初始代码。因此，在那里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中存储的内容进行渲染。

尝试将Page_PreRender中的代码放入Page_Load

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();  
    }  
}

对于排序方法，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();  
}

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();  
}
}
相关文章：