I have an ASP NET page with a dropdownlist. When the user select an item, a postback occurs, but it takes some time to receive the response, due to server processing. I want to show a label 'wait, reading data' or something, on the client side while waiting for the response. Have tried some samples but nothing, any help?
this, does not work
<script type="text/javascript" language="javascript">
function ShowConfirm(obj) {
document.getElementById("<%=Lbl_Buscar.ClientID%>").style.display = "none";
__doPostBack(obj.id, '');
}
</script>
CodePudding user response：
Actually, you can do this very easy with a button click, or in your case a dropdown.
The simple trick is that a button click, or even a dropdown can have BOTH a client side event, and the server side event.
This works for a button, or in this case a drop down.
so say this markup:
<div style="float:left;margin-top:18px">
<asp:DropDownList ID="cboHotels" runat="server"
Width="200px"
AutoPostBack="True"
OnSelectedIndexChanged="LBHotels_SelectedIndexChanged"
DataValueField="City"
DataTextField="City"
onchange="cbowait()">
</asp:DropDownList>
</div>
<div id="mywait" style="float:left;margin-left:25px;display: none">
<img src="../Content/wait2.gif" style="height: 62px; width: 75px" />
<asp:Label ID="Label1" runat="server" Text="Please wait..."
Font-Size="Large"></asp:Label>
</div>
<script>
function cbowait() {
$('#mywait').show()
}
</script>
<div style="clear:both"></div>
<br />
<asp:GridView ID="GridView1" runat="server"
CssClass="table table-hover" Width="35%">
</asp:GridView>
We have a dropdown list (combo box), then a "div" with text, picture (animated gif), or whatever for the please wait message.
but, note how we have both a client side, and server side event for the drop down list.
So, code behind is really simple. (since the post-back WHEN complete will re-load the page - and thus re-hide our message).
So, code behind is this:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// load up our combo box
string strSQL =
"select City from City order by City";
SqlCommand cmdSQL = new SqlCommand(strSQL);
cboHotels.DataSource = MyRstP(cmdSQL);
cboHotels.DataBind();
cboHotels.Items.Insert(0, new ListItem("Select hotel", ""));
}
}
DataTable MyRstP(SqlCommand cmdSQL)
{
DataTable rstData = new DataTable();
using (SqlConnection conn = new SqlConnection(Properties.Settings.Default.TEST4))
{
cmdSQL.Connection = conn;
using (cmdSQL)
{
conn.Open();
rstData.Load(cmdSQL.ExecuteReader());
}
}
return rstData;
}
protected void LBHotels_SelectedIndexChanged(object sender, EventArgs e)
{
string strSQL =
@"SELECT FirstName, LastName, City, HotelName, Description
FROM tblhotels WHERE City = @City";
SqlCommand cmdSQL = new SqlCommand(strSQL);
cmdSQL.Parameters.Add("@City", SqlDbType.NVarChar).Value = cboHotels.Text;
GridView1.DataSource = MyRstP(cmdSQL);
GridView1.DataBind();
System.Threading.Thread.Sleep(2000); // fake long delay
}
So, we "fake a 2 second delay
the result is thus this:
So, all you do is add a "div" with say a spinner and some text like "please wait...".
And note how ZERO changes was required to the server side (code behind) here.
I do this all the time for buttons, and the approach is just the same.
Eg this:
<asp:Button ID="Button1" runat="server" Text="Button"
OnClick="Button1_Click"
OnClientClick="cbowait();return true;"
/>
note how for the button, we MUST return "true" for the server side event to run. (and this feature can be rather handy, since you can then launch a js "confirm" dialog, and if the user hits no then you return false, and the server side button click does not run. Great for say a delete button.
CodePudding user response：
Thanks for your detailed response. The solution isnt working for me, after select the item in the dropdown, the page does not postback, not even display the mesage. I think it is because is inside a panel with a modalpopup extender. In fact, for the dropdown to work, I have to remove the onchange part.
<asp:Button ID="BtnShowPopUp4" runat="server" Text="Button" style="display:none" />
<cc1:ModalPopupExtender ID="ModalPopupExtenderNC" runat="server"
BackgroundCssClass="modalBackground"
DropShadow="True"
PopupControlID="PanelNC" TargetControlID="BtnShowPopUp4" CancelControlID="BtnCancelNC" >
</cc1:ModalPopupExtender>
<asp:Panel defaultbutton="BtnOkNC" ID="PanelNC" runat="server" CssClass="modalPopup"
Width="585px" >
<span style="text-decoration: underline; font-size: large">SOLICITUD NOTA DE CREDITO</span> <br />
<table style="width: 100%">
<tr>
<td style="width: 122px; text-align: left; "> </td>
<td style="text-align: left">
<asp:RadioButton ID="Rdr_USNC" runat="server" GroupName="Moneda" Text="US$" AutoPostBack="True" OnCheckedChanged="Rdr_USNC_CheckedChanged" />
<asp:RadioButton ID="Rdr_RDNC" runat="server" GroupName="Moneda" Text="RD$" AutoPostBack="True" OnCheckedChanged="Rdr_USNC_CheckedChanged" />
<div id="mywait" style="display: none">
<asp:Label ID="Lbl_Buscar" runat="server" style="font-weight: 700; color: #CC0000" Text="**Buscando Datos" ></asp:Label>
</div>
</td>
</tr>
<tr>
<td style="width: 122px; text-align: left; background-color: #74D1A3;"><b>
<asp:Label ID="Label4" runat="server" style="font-family: Arial, Helvetica, sans-serif; font-size: small" Text="Cliente"></asp:Label>
<asp:HyperLink ID="Hyp_Cod_Cliente" runat="server" Font-Bold="False" style="font-size: small"></asp:HyperLink>
</b></td>
<td style="text-align: left">
<asp:DropDownList ID="Cb_Clientes" runat="server" AutoPostBack="True" DataSourceID="DS_Clientes" DataTextField="wNombre"
DataValueField="Codigo" Font-Names="Arial" Font-Size="9pt" Height="25px" Width="350px"
OnSelectedIndexChanged="Cb_Clientes_SelectedIndexChanged" onchange="cbowait()" >
</asp:DropDownList>
<script type="text/javascript">
function cbowait() {
$('#mywait').show()
}
</script>
</td>
</tr>