Question

我使用asp dropbox并从数据库中填充dropbox。但是当点击按钮时dropbox的值发生变化因为按钮调用第一个pageload代码调用的when事件而在pageload中我从数据库中填充了dropbox 代码是

 protected void Page_Load(object sender, EventArgs e)
        {

        var q = from u in db.tbl_Subject select u;
        Paper_Subject.DataSource=q.ToList();
        Paper_Subject.DataTextField = "Subject_Name";
        Paper_Subject.DataValueField = "Subject_Id";
        Paper_Subject.DataBind();


        for (int i = 0; i <= 12;i++)
        {
            if(i<10)
                Paper_Duration_Hour.Items.Add("0"+i.ToString());
            else
                Paper_Duration_Hour.Items.Add(i.ToString());
        }
        for (int i = 0; i <= 60; i=i+5)
        {
            if(i<10)
                Paper_Duration_Minute.Items.Add("0"+i.ToString());
            else
                Paper_Duration_Minute.Items.Add(i.ToString());
        }
    }
protected void SaveData()
    {
        int PaperDurationHour;
        int PaperDurationMinute;
        int TeacherId;
        int SubjectId;
        tb.Paper_Name = PaperName.Text;
        if (int.TryParse(Paper_Duration_Hour.Text, out PaperDurationHour))
        {
            tb.Paper_Time_Hours = PaperDurationHour;
        }
        if (int.TryParse(Paper_Duration_Minute.Text, out PaperDurationMinute))
        {
            tb.Paper_Time_Minute = PaperDurationMinute;
        }
        string s1;
        s1 = Paper_Subject.SelectedItem.Text;
        var q = from u in db.tbl_Subject where u.Subject_Name.Equals(s1) select u;
        if (q.Count() > 0)
        {
            SubjectId = q.FirstOrDefault().Subject_Id;
            tb.Subject_Id = SubjectId;
        }
        if (int.TryParse(Session["TeacherID"].ToString(), out TeacherId))
        {
            tb.Teacher_Id = TeacherId;
        }
        db.tbl_Paper.Add(tb);
        db.SaveChanges();
    }
}

当按钮调用我想获取dropbox的选定值但每次因为pageload而得到第一个值

Answer 1

我建议您在首次加载页面时以及更改某些数据时填充Dropbox。要在页面首次加载时填充Dropbox，您可以使用属性IsPostBack，仅在首次加载页面时才为false，因此当您第一次加载页面时，语句(!IsPostBack)将返回true页。因此你可以这样做：

protected void Page_Load(object sender, EventArgs e)
{
     if(!IsPostBack)
     {
         //code here will be only executed the first time the page is loaded
         var q = from u in db.tbl_Subject select u;
         Paper_Subject.DataSource=q.ToList();
         Paper_Subject.DataTextField = "Subject_Name";
         Paper_Subject.DataValueField = "Subject_Id";
         Paper_Subject.DataBind();

         for (int i = 0; i <= 12;i++)
         {
             if(i<10)
                 Paper_Duration_Hour.Items.Add("0"+i.ToString());
             else
                 Paper_Duration_Hour.Items.Add(i.ToString());
         }
         for (int i = 0; i <= 60; i=i+5)
         {
             if(i<10)
                 Paper_Duration_Minute.Items.Add("0"+i.ToString());
             else
                 Paper_Duration_Minute.Items.Add(i.ToString());
         }
     }
    //code here will be executed every time page loaded
}

，代码只会在您第一次加载页面时执行。

由于页面加载，按钮单击后Dropbox值更改

1 个答案: