Question

我正试图从一个简单的asp.net表单中保存价值。

我在网页上几乎没有像下拉菜单那样的控件。文本框的

我在页面加载时填写第一个下拉菜单＆Language;触发后晒，以填充第二个下拉列表ddCategoryType，它根据所选语言填充正确的值，但问题是当我尝试获取ddCategoryType.SelectedItem的按钮点击事件值的值。由于某些我现在无法弄清楚的原因，值总是返回0

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        ddSelectLanguage.Items.Clear();
        ddSelectLanguage.DataSource = DataProvider.GetLanguages();
        ddSelectLanguage.DataBind();
        ddSelectLanguage.Items.Insert(0, new ListItem("Select Language", "0"));
    }
    else
    {
        ddCategoryType.Items.Clear();
        String strSql = "SELECT TypeName, TypeID FROM  CategoryType WHERE LangID =" + ddSelectLanguage.SelectedItem.Value.ToString();
        DataSet ds = new DataSet();
        ds = DataProvider.Connect_Select(strSql);
        ddCategoryType.DataSource = ds;
        ddCategoryType.DataBind();
        ddCategoryType.Items.Insert(0, new ListItem("Select Type", "0"));
    }
}


protected void btnSaveCategory_Click(object sender, EventArgs e)
{
    objArtCat.LanguageID = int.Parse(ddSelectLanguage.SelectedItem.Value.ToString());
    objArtCat.CategoryName = txtCategoryName.Text;
    objArtCat.CategoryType = int.Parse(ddCategoryType.SelectedItem.Value.ToString());
    objArtCat.CategoryActive = bool.Parse(ddCategoryActive.SelectedItem.Value.ToString());
    try
    {
        //bool result;
        //result = objBLAddArticleCategory.CreateNewArticleCategory(objArtCat);
        //if (result == true)
        //{
        //    Response.Redirect("PageMessage.aspx?msg='Category has been Create Successfully'", true);
        //}
        //else
        //{
        //}
    }
    catch (Exception)
    { }
}

SAMPLE .ASPX CODE

   <div  class="row"></div>
              <div class="row">
            <asp:Label ID="lblSelectLang" CssClass="txtLabel"  Text="Select Language  :" runat="server" ></asp:Label>
            <asp:DropDownList ID="ddSelectLanguage" runat="server" CssClass="ddGeneral" 
                      DataTextField="LangName" DataValueField="LangID" CausesValidation="True" 
                      AutoPostBack="True"  >
            </asp:DropDownList>
         <asp:RequiredFieldValidator ID="rfvddLanguage" runat="server" ErrorMessage="Please Select Language"  ControlToValidate="ddSelectLanguage" 
         InitialValue="Select Language" ValidationGroup="atpAddNewArticle" ></asp:RequiredFieldValidator>
       </div>

       <div class="row">
            <asp:Label ID="lblCategoryName" CssClass="txtLabel" runat="server" Text="Category Name :"></asp:Label>
            <asp:TextBox ID="txtCategoryName" runat="server" CssClass="txtbox300"></asp:TextBox>
            <asp:RequiredFieldValidator ID="RFVtxtAuthorName" runat="server" ErrorMessage="*" 
                ControlToValidate="txtCategoryName" ValidationGroup="atpAddNewArticle"  CssClass="validation"></asp:RequiredFieldValidator>
       </div>

       <div class="row">
            <asp:Label ID="lblCategoryType" CssClass="txtLabel" runat="server" Text="Category Type :"></asp:Label>
            <asp:DropDownList ID="ddCategoryType" runat="server" CssClass="ddGeneral"   DataTextField="TypeName" DataValueField="TypeID" >
            </asp:DropDownList>
       </div>

       <div class="row">
            <asp:Label ID="lblCategoryActive" CssClass="txtLabel" runat="server" Text="Category Active :"></asp:Label>
            <asp:DropDownList ID="ddCategoryActive" runat="server" CssClass="ddGeneral"  >
                <asp:ListItem Value="False" Selected="True">NO</asp:ListItem>
                <asp:ListItem Value="True">YES</asp:ListItem>
            </asp:DropDownList>
       </div>

       <div class="rowButton">
            </br>
            <asp:Button ID="btnUpdateArticle" runat="server" Text="Save Category" CssClass="btn"  ValidationGroup="atpAddNewArticle" onclick="btnSaveCategory_Click" />                <input id="Reset" type="reset" class="btn" value="Reset" />
       </div>

回发后的ddCategoryType的OutPut

<div class="row">
                <span class="txtLabel" id="MainContent_lblCategoryType">Category Type :</span>
                <select class="ddGeneral" id="MainContent_ddCategoryType" name="ctl00$MainContent$ddCategoryType">
    <option value="0" selected="selected">Select Type</option>
    <option value="1">Article</option>
    <option value="2">News</option>
    <option value="3">Sports</option>
    <option value="4">People</option>
    <option value="5">Message</option>

</select>
           </div>

Answer 1

在Page_Load中，您正在清除ddCategoryType的内容，因此SelectedIndex将重置为0.

请记住，总是调用Page_Load，它会在Button_Click事件之前发生。

有几种方法可以解决这个问题，例如：如果SelectedIndex >= 0

，请不要在Page_Load的 else 子句中执行所有代码

Answer 2

由于您希望根据ddSelectLanguage中的选定值填充ddCategoryType，然后根据该交互填充DDL，而不是在Page_Load中填充。

protected void Page_Load(object sender, EventArgs e)
{
    ddSelectLanguage.SelectedIndexChanged += new
        EventHandler(ddSelectLanguage_SelectedIndexChanged);
    if (!IsPostBack)
    {
        ddSelectLanguage.Items.Clear();
        ddSelectLanguage.DataSource = DataProvider.GetLanguages();
        ddSelectLanguage.DataBind();
        ddSelectLanguage.Items.Insert(0, new ListItem("Select Language", "0"));
    }
}

然后

 void ddSelectLanguage_SelectedIndexChanged(object sender, EventArgs e)
 {
        ddCategoryType.Items.Clear();
        String strSql = "SELECT TypeName, TypeID FROM  CategoryType WHERE LangID =" + ddSelectLanguage.SelectedItem.Value.ToString();
        DataSet ds = new DataSet();
        ds = DataProvider.Connect_Select(strSql);
        ddCategoryType.DataSource = ds;
        ddCategoryType.DataBind();
        ddCategoryType.Items.Insert(0, new ListItem("Select Type", "0"));
 }

另外，让您的查询获取参数。

ASP.Net下拉列表始终返回按钮单击事件的第一个值

2 个答案: