asp.net - ASP.Net下拉菜单始终在按钮单击事件中返回第一个值

我试图从一个简单的asp.net表单中保存价值。

我在页面上没有几个控件，例如下拉菜单和文本框

我用语言填充页面加载中的第一个下拉列表并在其上触发后沉以填充第二个下拉列表ddCategoryType，它根据所选语言填充了正确的值，但是问题是当我尝试获取ddCategoryType.SelectedItem.Value在按钮单击事件值上的值由于某些原因总是返回0，我现在无法确定

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)
    { }
}

样本.ASPX代码

   <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>

最佳答案

由于您要基于ddSelectLanguage中的选定值填充ddCategoryType，因此请基于该交互而不是Page_Load中的DDL进行填充。

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，使查询采用参数。