不从下拉菜单中获取当前文本的代码背后

MatiasP 发表于 Dev

马蒂亚斯

我的按钮和下拉菜单有问题，当我单击按钮并在后面的代码中调用一个方法时，后面的代码不是采用下拉菜单的当前文本，而是采用刷新网站后的文本。的aspx代码是：

<form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager" EnablePageMethods="true" runat="server" />
<div>
    <table runat="server" id="showDBTable">
        <tr>
            <td>
                <asp:Button ID="showDB" runat="server" OnClick="showDBContent" Text="Show database content" />
            </td>
            <td>
                <asp:DropDownList runat="server" ID="showDBDropDown" OnLoad="FindExistingMetaTag" />
            </td>
        </tr>
    </table>
</div>
</form>

以及后面的代码：

protected void showDBContent(object sender, EventArgs e)
{
    String queryString = "";
    if (showDBDropDown.Text == "Show all")
    {
        queryString = "SELECT * from dbo.Search";
    }
    else
    {
        queryString = "SELECT * from dbo.Search where Tag = '" + (showDBDropDown.Text).TrimStart().TrimEnd() + "'";
    }

我该如何解决？

编辑-根据要求：

    protected void FindExistingMetaTag(object sender, EventArgs e)
{
    String queryString = "SELECT TAG from dbo.Tags";
    List<String> tagsShow = new List<String>();
    tagsShow.Add("Show all");
    using (SqlConnection conn = new SqlConnection(info.connectionString))
    using (var cmd = conn.CreateCommand())
    {
        conn.Open();
        cmd.CommandText = queryString;
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                tagsShow.Add(reader.GetString(0));
            }
        }
    }

    showDBDropDown.DataSource = tagsShow;
    showDBDropDown.DataBind();
    showDBDropDown.SelectedIndex = 0;
}

我只是注意到它可能是“ showDBDropDown.SelectedIndex = 0;”，但是它似乎并没有改变任何东西来将其删除。

依卡德

我认为您需要从中删除该OnLoad属性showDBDropDown：

<asp:DropDownList runat="server" ID="showDBDropDown" />

并在第一次加载时填充showDBDropDowninPage_Load方法的内容，如下所示：

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindDropdowns();
    }
}

private void BindDropdowns()
{
    String queryString = "SELECT TAG from dbo.Tags";
    List<String> tagsShow = new List<String>();
    tagsShow.Add("Show all");
    using (SqlConnection conn = new SqlConnection(info.connectionString))
    using (var cmd = conn.CreateCommand())
    {
        conn.Open();
        cmd.CommandText = queryString;
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                tagsShow.Add(reader.GetString(0));
            }
        }
    }

    showDBDropDown.DataSource = tagsShow;
    showDBDropDown.DataBind();
}