Question

我试图在按下按钮时在下拉菜单中分配所选值。我无法在TextBox中看到所选的值。有人可以让我知道我错过了什么吗？

我的代码如下：

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {                       

    }

    protected void Button1_Click1(object sender, EventArgs e)
    {

        string strConn = "Initial Catalog=NavigateV6;Data Source=SVUSRYE-SQL3D1;User ID=dopis_user;Password=dopis_password;Persist Security Info=True;MultipleActiveResultSets=True";
        SqlConnection mycn = new SqlConnection(strConn);
        DataSet ds = new DataSet();
        SqlDataAdapter myda = new SqlDataAdapter("Select accountid FROM trn_account ", mycn);
        myda.Fill(ds);
        DDL.DataSource = ds;
        DDL.DataTextField = "AccountID";
        DDL.DataValueField = "AccountID";
        DDL.DataBind();

    }



    protected void DDL_SelectedIndexChanged(Object sender, EventArgs e)
    {
        var selectedValue = ((DropDownList)sender).SelectedValue;
        if (!string.IsNullOrEmpty(TextBox1.Text))
            TextBox1.Text = selectedValue;

    }
}

ASPX：

<asp:DropDownList ID="DDL" runat="server" AutoPostBack="True" OnSelectedIndexChanged = " DDL_SelectedIndexChanged" >

    </asp:DropDownList>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <br />
    <br />
    <br />
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click1" 
        Text="sumbit" />
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <br />
</asp:Content>

Answer 1

jQuery可以在没有回发的情况下快速完成：

$('#<%= ButtonID.ClientID %>').click(function() {
    $('#<%= TextBoxID.ClientID %>').val($('#<%= DDL_ID.ClientID %>').val());
    return false;
});

实际上你甚至不需要点击按钮，当用户在ddl中选择一个新值时就可以完成：

$('#<%= DDL_ID.ClientID %>').change(function() {
    $('#<%= TextBoxID.ClientID %>').val($(this).val());
});

Answer 2

你的问题是因为当你检查(!string.IsNullOrEmpty(TextBox1.Text))时，它总是返回false，因为在第一阶段，TextBox的值为空，因此永远不会执行if condition的内部代码.....如果你需要经历上述条件，你可以在声明时在TextBox中加上一些价值.......

或者，

只需在SelectedIndexChanged

的DropDownList中执行此操作即可

 var selectedValue = ((DropDownList)sender).SelectedValue;
 TextBox1.Text = selectedValue;

以下是与您的代码类似的工作示例：

ASPX：

<body>
  <form runat="server" id="form1">
        <asp:DropDownList ID="DDL" runat="server" AutoPostBack="True" 
        OnSelectedIndexChanged = "DDL_SelectedIndexChanged" >
      <asp:ListItem Value="One">One</asp:ListItem>
      <asp:ListItem Value="Two">Two</asp:ListItem>
    </asp:DropDownList>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <br />
    <br />
    <br />
    <asp:Button ID="Button1" runat="server" 
        Text="sumbit" onclick="Button1_Click" />
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <br />
  </form>
</body>

代码背后：

 public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {

        }

        protected void DDL_SelectedIndexChanged(object sender, EventArgs e)
        {
            var selectedValue = ((DropDownList)sender).SelectedValue;
            TextBox1.Text = selectedValue;
        }
    }

如何将选定的下拉值分配给文本框

2 个答案: