如何在asp.net 中更改label.text？

Question

I'm trying to change a label text from cs file after I receive a message from the server. I tried using to put the label in updatepanel but couldn't make it work. How can i update the display of the label?

Answer 1

Usually this is something along the lines of

myLabel.Text = "Value";

If it's in an UpdatePanel, the rules are a little different. I think you need to get the control, then update its value. Something along the lines of:

Label lbl = (Label) updatePanel1.FindControl("myLabel");
lbl.Text = "Value";

Answer 2

If you are trying to avoid a post back, then you can use ASP.NET AJAX Page Methods to query the server via AJAX and then push the value returned into the label control, like this:

Markup:

<script type="text/javascript">
    $(document).ready(function () {
        $('.TheButton').click(function () {
            $.ajax({
                type: "POST",
                url: "Default.aspx/GetDate",
                data: "{}",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (data) {
                    $('.TheLabel').text(data.d);
                }
            });

            return false;
        });
    });
</script>
<asp:Label ID="Label1" runat="server" Text="Nothing" CssClass="TheLabel" />
<br/>
<asp:Button runat="server" ID="Button1" CssClass="TheButton" Text="Update Label"/>

Code-behind:

[WebMethod]
public static string GetDate()
{
    return DateTime.Now.ToString();
}

Note: ASP.NET AJAX Page Methods are static methods that are not part of the ASP.NET page life-cycle. They do not have access to any of the controls on the page, but are very useful for getting data from the server (in this case the server time). In the interest of simplicity, I used CSS class names on the server controls to make the jQuery selectors simpler.