c# - 在 page_load 上传递内容页上的母版页控件值

Question

我在母版页上有一个下拉列表，我想在加载内容页时传递内容页上的选定值。我的问题是，只有当我更改下拉列表中的值时，该值才会传递。因此，当页面加载时，我必须从下拉列表中重新选择以捕获下拉列表的值。如果我正在浏览内容页面，则所选值不会在页面加载时传递。我的母版页代码 .net:

<asp:DropDownList ID="ddlcategories" 
        runat="server" DataSourceID="SqlDataSourcecategories" DataTextField="CategoryName" 
        DataValueField="CategoryID" AutoPostBack="True" 
        onselectedindexchanged="ddlcategories_SelectedIndexChanged"></asp:DropDownList>

母版页:

protected void Page_Load(object sender, EventArgs e)
{
 if (!IsPostBack)
 {    
      ddlcategories.DataBind();
      ddlcategories.Items.Insert(0, "Uncategorized");
      ddlcategories.Items[0].Value = "0";
      ddlcategories.SelectedValue = Convert.ToString(Session["lblCategoryID"]);
  }
}
protected void ddlcategories_SelectedIndexChanged(object sender, EventArgs e)
{
    Session["lblCategoryID"] = Convert.ToInt32(ddlcategories.SelectedValue);
}

内容页cs:

protected void Page_Load(object sender, EventArgs e)
{                
    Label10.Text = Convert.ToString(((DropDownList)Master.FindControl("ddlcategories")).SelectedValue);                 
}

Answer 1

试试这个解决方案:

母版页:

<asp:DropDownList ID="ddlcategories" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlcategories_SelectedIndexChanged">
    <asp:ListItem>One</asp:ListItem>
    <asp:ListItem>Two</asp:ListItem>
</asp:DropDownList>

母版页 CS:

public string SelectedValue
{
    get
    {
        return ddlcategories.SelectedValue;
    }
    set
    {
        ddlcategories.SelectedValue= value;
    }
}

protected void ddlcategories_SelectedIndexChanged(object sender, EventArgs e)
{
    SelectedValue = ddlcategories.SelectedValue;
}

内容页面标记:

<%@ MasterType VirtualPath="~/Site1.Master" %>

<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>

内容页CS。

protected void Page_PreRender(object sender, EventArgs e)
{
    Label1.Text = Master.SelectedValue;
}

注意:值只是为了演示，您可以在下拉列表中使用实际的数据源值。