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How to call CascadingDropDown ServiceMethod at on click

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User1503019091 posted

Is it possible to load the content of CascadingDropDown ServiceMethod when the client user click the drop down?

I have this CascadingDropDown with ServiceMethod="GetCarMakes". GetCarMakes is called when the control is loaded. but I want it to only load when user click the down arrow.. is this possible?

thank you

my environment is ASP.net with VB.net code behind

Friday, June 12, 2015 3:58 PM

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User1644755831 posted

Hello WWI Armando,

Please see this Link: https://support.microsoft.com/en-us/kb/976156

As described in the article right now he is loading the initial dropdown on page load event like this.

 function pageLoad() {
            // call a Web service method with no parameters and the user context.
            KB_CascadingDDL_VB.WebService.GetMakeValue(SucceededCallbackWithContext, FailedCallback, "fillMake");
        }

You could change this to as following using javascript and use onmousedown event.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm44.aspx.cs" Inherits="WebFormsIdentity.WebForm44" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title></title>
  <script src="Scripts/jquery-2.1.3.min.js"></script>
  <script>
    var selectloaded = false;

    function onmousedownevent() {
      if (!selectloaded) {
        var data = ['1', '2', '3']; //get this from webservice
        $.each(data, function () {
          $('#select').append($('<option>').val(this).text(this));
        })
        selectloaded = true;
      }

    }
    function onchanged() {
      alert($(this).val());
    }
  </script>

</head>
<body>
  <form id="form1" runat="server">
    <div>
      <select id="select" onmousedown="onmousedownevent()" onchange="onchanged()"></select>
    </div>
  </form>
</body>
</html>

On Mouse down event it will load the dropdown.

Hope this helps.

With Regards,

Krunal Parekh

Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM

Sunday, June 14, 2015 11:30 PM

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User1644755831 posted

Hello WWI Armando,

WWI Armando
t.ServicePath = "AutoComplete.asmx" t.ServiceMethod = "GetCarMake"

You can remove the service call and add the client side call using WebControl.Attributes Property.

Please see: How to: Set HTML Attributes for Controls in ASP.NET Web Pages using this you can bind client side mousedown event that I described earlier.

Hope this helps.

With Regards,

Krunal Parekh
- Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
Sunday, June 28, 2015 10:38 PM

All replies

User1644755831 posted

Hello WWI Armando,

Please see this Link: https://support.microsoft.com/en-us/kb/976156

As described in the article right now he is loading the initial dropdown on page load event like this.

 function pageLoad() {
            // call a Web service method with no parameters and the user context.
            KB_CascadingDDL_VB.WebService.GetMakeValue(SucceededCallbackWithContext, FailedCallback, "fillMake");
        }

You could change this to as following using javascript and use onmousedown event.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm44.aspx.cs" Inherits="WebFormsIdentity.WebForm44" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title></title>
  <script src="Scripts/jquery-2.1.3.min.js"></script>
  <script>
    var selectloaded = false;

    function onmousedownevent() {
      if (!selectloaded) {
        var data = ['1', '2', '3']; //get this from webservice
        $.each(data, function () {
          $('#select').append($('<option>').val(this).text(this));
        })
        selectloaded = true;
      }

    }
    function onchanged() {
      alert($(this).val());
    }
  </script>

</head>
<body>
  <form id="form1" runat="server">
    <div>
      <select id="select" onmousedown="onmousedownevent()" onchange="onchanged()"></select>
    </div>
  </form>
</body>
</html>

On Mouse down event it will load the dropdown.

Hope this helps.

With Regards,

Krunal Parekh

Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM

Sunday, June 14, 2015 11:30 PM

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User1503019091 posted

the control is dynamically added. in that case how do I add onmouseDown attributes to the cascading dropdown control?

thank you

Friday, June 19, 2015 2:35 PM
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User1644755831 posted

Hello WW! Armando,

Please Post your code on how you are adding dynamic controls.

With Regards,

Krunal

Sunday, June 21, 2015 9:56 PM

User1503019091 posted

this is the HTML

<asp:Table ID="tblDetail" runat="server">
</asp:Table>

VB.net

Private Sub LoadForm()
  For Each drv As Data.DataRowView In ds.CarDS.DefaultView
    Dim dr As dsCar.ExpenseRow = drv.Row
    AddLine(dr)
  Next
End Sub

Sub AddLine(ByVal dr As dsCar.CarMakeRow)
  Dim cboCar As New DropDownList
  Dim tr As New TableRow
  Dim tc As New TableCell
  Dim s as String
  s = dr.CarMake
  tc.Controls.Add(cboCar)
  tc.Controls.Add(getCascade(cboCar,s))
  tr.Cells.Add(tc)
  tblDetail.Rows.Add(tr)
End Sub

Function getCascade(ByVal dl As DropDownList, ByVal SelectedValue As String) As AjaxControlToolkit.CascadingDropDown
  Dim t As New AjaxControlToolkit.CascadingDropDown
  t.ID = "Z" & dl.ID
  t.TargetControlID = dl.ID
  t.ServicePath = "AutoComplete.asmx"
  t.ServiceMethod = "GetCarMake"
  t.Category = "CarMake"
  t.PromptText = "-"
  t.LoadingText = "[Reading projects...]"
  t.selectedvalue =  selectedValue
  Return t
End Function

This is the ASMX file

%@ WebService Language="VB" CodeBehind="~/App_Code/AutoComplete.vb" Class="AutoComplete" %>

This is the AutoComplete.VB

    <WebMethod()> <Script.Services.ScriptMethod()> _
    Public Function GetCarMake(ByVal knownCategoryValues As String, ByVal category As String) As AjaxControlToolkit.CascadingDropDownNameValue()
        Dim dt As New dsCar.v_Car_ProjectDataTable
        Dim da As New dsCarTableAdapters.v_Car_ProjectTableAdapter
        Dim kv As StringDictionary = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues)
        If Not kv.ContainsKey("CarMake") Then Return Nothing
        da.FillByCpny(dt, kv("CarMake"))
        da.Connection.Close()
        Dim values As New List(Of AjaxControlToolkit.CascadingDropDownNameValue)
        For Each dr As dsExpense.v_Car_ProjectRow In dt.Rows
            values.Add(New AjaxControlToolkit.CascadingDropDownNameValue(dr.CarMake.Trim , dr.CarMake.Trim))
        Next
        Return values.ToArray()
    End Function

The code above works. but The problem I have with this is when my datatable has 100 lines, it will try to load the GetCarMake 100 times, this often crash IE.

SO if I could find a way to call getCarMake only when the drop down is clicked I think I will be golden. but I am open for suggestion.

Thursday, June 25, 2015 5:48 PM

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User1644755831 posted

Hello WWI Armando,

WWI Armando
t.ServicePath = "AutoComplete.asmx" t.ServiceMethod = "GetCarMake"

You can remove the service call and add the client side call using WebControl.Attributes Property.

Please see: How to: Set HTML Attributes for Controls in ASP.NET Web Pages using this you can bind client side mousedown event that I described earlier.

Hope this helps.

With Regards,

Krunal Parekh
- Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
Sunday, June 28, 2015 10:38 PM
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User1503019091 posted

Do I add the onClick attributes to cboCar or the CascadingDropDown?

If to CascadingDropDown .. I tried two below but both are invalid syntax

t.attributes("onclick")="javascript:alert('test');" and t.attributes.add("onClick", "Alert('test')")

so I am guessing the attributes is to cboCar?

Friday, July 3, 2015 2:36 PM
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User1644755831 posted

Hello,

WWI Armando

or the CascadingDropDown?

You really don't need the CascadingDropDown here you can achieve this using just the dropdown as I described earlier using javascript and mousedown event.

Calling of the webservice will be handled client side.
Sunday, July 5, 2015 9:32 PM

Answered by:

How to call CascadingDropDown ServiceMethod at on click

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WWI Armando

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WWI Armando

WWI Armando