CascadingDropDown: items

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Saturday, March 24, 2012

CascadingDropDownList and a MySQL database

How to use CascadingDropDownLists bound to a MySQL-database? I want a parent DDList with items selected from one table and a second DDlist with items selected from another table based on the value selected in the first one. But how to write the asmx-file?

Hi,

First, you can refer to this documentation for how to use it with a database. http://ajax.asp.net/ajaxtoolkit/Walkthrough/CCDWithDB.aspx

Then, as far as I know, MySql provides db driver for .net which can be used in a similar way as the build-in ADO.NET does. You can download it from their website and try to implement it according to the above documentation.

Hope this helps.

CascadingDropDownList - cant handle more than 765 items!

Hello,

My CascadingDropDownList gives me Method 500 error when more than 765 items are returned from the webservice! Is there a way to fix this? Thanks..

Hi,

that's probably related with the limit for the max size of the JSON payload set by ASP.NET AJAX. You can change it in the web.config:

this certainly worked! thank you!
Thanks! Helped me alot.
I have tried putting that in every section and it always errors out as unkown element, if someone can help I would really appreciate it!

Hi,

it must be added inside the configuration -> system.web.extensions -> scripting -> webServices section.

Thank you!

Hi,

I have changed the web config maxJsonLength to 1000. But i dont have that many values. First dropdown is giving me a value but on the second dropdown I am getting method error 500. My webservice code is as follows.

Imports

System.Web
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Xml

<WebService(Namespace:=

"http://tempuri.org/")> _
<System.Web.Script.Services.ScriptService()> _

Public

Class MIService
Inherits System.Web.Services.WebService
Shared _DocumentAs XmlDocument
Shared _lockAsNewObject
PublicReadOnlyProperty Document()As XmlDocument
Get
If (_DocumentIsNothing)Then
SyncLock _lock
_Document =New XmlDocument
_Document.Load(HttpContext.Current.Server.MapPath("~/App_Data/MIService.xml"))
EndSyncLock
EndIf
Document = _Document
ExitProperty
EndGet
EndProperty
PublicReadOnlyProperty Hierarchy()AsString()
Get
Dim _HeirarchyAsString() = {"city","zip"}
Return _Heirarchy
EndGet
EndProperty
<WebMethod()> _
PublicFunction GetDropDownContents(ByVal knownCategoryValuesAsString,ByVal categoryAsString)As AjaxControlToolkit.CascadingDropDownNameValue()
'Get a dictionary of known category/value pairs
Dim knownCategoryValuesDictionaryAsNew StringDictionary
knownCategoryValuesDictionary = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues)' Perform a simple query against the data document
Return AjaxControlToolkit.CascadingDropDown.QuerySimpleCascadingDropDownDocument(Document, Hierarchy, knownCategoryValuesDictionary, category)
EndFunction
EndClass

My code for aspx file is:

@.PageLanguage="VB"AutoEventWireup="true"CodeFile="Default.aspx.vb"Inherits="_Default"EnableEventValidation="False"%>
<%@.RegisterAssembly="AjaxControlToolkit"Namespace="AjaxControlToolkit"TagPrefix="cc1" %>
<!DOCTYPEhtmlPUBLIC"-//W3C//DTD XHTML 1.1//EN""http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

htmlxmlns="http://www.w3.org/1999/xhtml">
<headrunat="server">
<title>Untitled Page</title>
<scriptrunat="server">
<System.Web.Services.WebMethod()> _
<System.Web.Script.Services.ScriptMethod()> _
PublicSharedFunction GetDropDownContentsPageMethod(ByVal knownCategoryValuesAsString,ByVal categoryAsString)As AjaxControlToolkit.CascadingDropDownNameValue()
ReturnNew MIService().GetDropDownContents(knownCategoryValues, category)EndFunction
</script>
</head>
<body>
<formid="form1"runat="server">
<asp:ScriptManagerID="ScriptManager1"runat="server"/>
<div>
<asp:UpdatePanelID="UpdatePanel1"runat="server">
<ContentTemplate>
<asp:DropDownListID="DropDownList1"runat="server"Width="200px">
</asp:DropDownList><br/>
<asp:DropDownListID="DropDownList2"runat="server"Width="200px">
</asp:DropDownList><br/>
<asp:DropDownListID="DropDownList3"runat="server"AutoPostBack="True"Width="200px">
</asp:DropDownList><br/>
<br/>
<asp:LabelID="Label1"runat="server"Width="224px"></asp:Label><br/>
<br/>
<cc1:CascadingDropDownID="CascadingDropDown1"runat="server"Category="city"LoadingText="[loading City...]"PromptText="Please select a city."ServiceMethod="GetDropDownContents"ServicePath="MIService.asmx"TargetControlID="DropDownList1"></cc1:CascadingDropDown><cc1:CascadingDropDownID="CascadingDropDown2"runat="server"Category="zip"LoadingText="[Loading Zip...]"ParentControlID="DropDownList1"PromptText="Please enter zip."ServiceMethod="GetDropDownContentPageMethod"TargetControlID="DropDownList2"></cc1:CascadingDropDown><cc1:CascadingDropDownID="CascadingDropDown3"runat="server"Category="county"LoadingText="[loading County..]"ParentControlID="DropDownList2"PromptText="Please select county."ServiceMethod="GetDropDownContents"ServicePath="MIService.asmx"TargetControlID="DropDownList3"></cc1:CascadingDropDown>
<br/>
<br/>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
</body>
</html>

Hi,

Imports

System.Web
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Xml

<WebService(Namespace:=

"http://tempuri.org/")> _
<System.Web.Script.Services.ScriptService()> _

Public

My code for aspx file is:

Thank You,

Nepalaya

Hi,

what's the content of the 500? You can useFiddler to examine it.

I hope u get it the way you want, but 765 items in a drop down list isn't very user friendly? Think about screen res?

Maybe test out autocomplete control?

Just giving my view, but if you want 1000 items in a drop down list, go for it :P (I know how annoying it is when people try to divert you from the solution you want, so go for what is best in your app, just throwing out a suggestion)

Hi,

The problem resolved. It was not related with the lenght. Page method was not working so change the service method name to GetDropDownContents and it works.

cc1:CascadingDropDownID="CascadingDropDown1"runat="server"Category="city"LoadingText="[loading City...]"PromptText="Please select a city."ServiceMethod="GetDropDownContents"ServicePath="MIService.asmx"TargetControlID="DropDownList1">
</cc1:CascadingDropDown><cc1:CascadingDropDownID="CascadingDropDown2"runat="server"Category="zip"LoadingText="[Loading Zip...]"ParentControlID="DropDownList1"PromptText="Please enter zip."ServicePath="MIService.asmx"ServiceMethod="GetDropDownContents"TargetControlID="DropDownList2">
</cc1:CascadingDropDown>

Thanks,

Nepalaya

Hello freinds,

I am not able to fill the cascading drop down using database. Does any one have fill it with the database??

Please help me i am stuck with this problem.

Thaks in advance.

Hi,

I get method error 500 in dropdownlist1 . Iam using WEB SERVICE .

i used <jsonSerializationmaxJsonLength="500" /> in web.config but still i get the error.

Can any one help ?

Thanks

CascadingDropDown with two items containing the same value

I'd like to create a cascading drop down control with two list items that have the same value and also be able to programmatically populate the drop down via the selected item's text. I haven't seen anything like this and I can't see a way to do it.

In the sample pages I've changed the CarService.xml file as follows:

1 <make name="Audi" value="Audi (value)">2 <model name="A4" value="A4 (value)">3 <color name="Azure" value="Azure (value)" />4 <color name="Light Azure" value="Light Azure (value)" />5 <color name="Dark Azure" value="Dark Azure (value)" />6 <color name="Test Azure" value="Dark Azure (value)" />7 </model>

...adding the "Test Azure" color node with the same value as "Dark Azure". Note that when you select "Dark Azure" on the page, then select "Test Azure", theDropDownList3_SelectedIndexChanged event doesn't fire.

Does anyone know how to do this?

Hi,

I tried it, it worked fine.

I add the line

<color name="Test Azure" value="Dark Azure (value)" /> to the xml file as you described, and didn't modify a line of code.

I tried it again and still no dice. It may not be possible:

I created the following page to test regular asp.net...

<%@. Page Language="C#" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><script runat="server"> protected void ddlTest_SelectedIndexChanged(object sender, EventArgs e) { Label1.Text = String.Format("{0} - {1}", ddlTest.SelectedIndex, ddlTest.SelectedValue); }</script><html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server"> <title>Untitled Page</title></head><body> <form id="form1" runat="server"> <div> <asp:DropDownList ID="ddlTest" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlTest_SelectedIndexChanged"> <asp:ListItem Text="Apple" Value="Red"></asp:ListItem> <asp:ListItem Text="Banana" Value="Yellow"></asp:ListItem> <asp:ListItem Text="Apple Again" Value="Red"></asp:ListItem> </asp:DropDownList> <asp:Label ID="Label1" runat="server"></asp:Label> </div> </form></body></html>

Notice that selecting "Apple Again" will autopostback with "Apple" selected. I'll look for another solution.

That's because "apple" and "apple again" have the same value.

CascadingDropDown slow to load in IE7?

I have a cascading dropdown that loads about 13,000 items from a PageMethod. In Firefox 2 this takes just under 5 seconds, but the same page in IE7 is taking about 160 seconds to load the same dropdown! IE response to using that page is also slow once it has loaded.

If I populate the dropdown server-side by binding a datasource directly to the control is takes a while to render the page but nowhere near 2.5 minutes.

Code example:

HTML:

<asp:dropdownlist id="ddlAlert" runat="server" width="100%"></asp:dropdownlist>
<ajt:CascadingDropDown ID="cddAlerts" runat="server" TargetControlID="ddlAlert" Category="Alert" ServiceMethod="GetAlerts" LoadingText="Loading alerts..." />

Code Behind:

 <System.Web.Services.WebMethod()> _
 <System.Web.Script.Services.ScriptMethod()> _
Public Shared Function GetAlerts(ByVal knownCategoryValuesAs String,ByVal categoryAs String)As CascadingDropDownNameValue()
Dim retValAs New Collections.Generic.List(Of CascadingDropDownNameValue)
 retVal.Add(New CascadingDropDownNameValue("All Alerts","0",True))
Dim appAs New MOAE.MOAE
Dim dsAs DataSet = app.GetAlertProfiles
Try
 For Each rowAs DataRowIn ds.Tables(0).Rows
 retVal.Add(New CascadingDropDownNameValue(row("AlertDisplayName").ToString, row("AlertProfileID").ToString))
Next
 Catch exAs Exception
 app.LogWarning(ex, Diagnostics.EventLogEntryType.Error)
End Try ds =Nothing app =Nothing
 Return retVal.ToArray
End Function

Does anyone have any way of speeding this up? Is this just down to IE's Javascript engine?

Cheers,
Nick

I know this isn't the answer you want to hear, but as a user I would cringe at a dropdown containing 13k items. How would I ever find the item I'm looking for. Isn't there a better design implementation?

I don't know but I could certainly see IE having a heart attack with a 13k dropdown and that would account for the slow page. Might not be completely fixable if that's the case...

It's the conclusion I had come to as well but I was curious at the disparity in speed between Firefox's and IE's implementation of this....

Hi Nickfoster,

IE7 and Firefox are have their own merits. Some tests show that Firefox do better job on string processing. But I am quite agree with Noahb, we should limit its items in your case.

Best regards,

Jonathan

Wednesday, March 21, 2012

CascadingDropDown items limited (Error) ??

Hello people,

I have a big problem with CDD, try to load a large amount of items, for example.

In the sample of CDD change the webservice "CarsService" method "GetDropDownContents",
insert this code:

for (int i = 0; i < 870; i++)
{
values.Add(new CascadingDropDownNameValue(string.Format("Name{0}",i), string.Format("Value{0}",i)));
}

and the Method Erro 500 show ...

my list are 890 items

Please Help...! Idea

What is the exact error you are getting? Is it possible to figure out at what exact number of items cdd starts to error out?

Also, what is the scenario in which you need to have so many items in a cdd? From a usability point of view it does not seem very appropriate.

Try:http://ajax.asp.net/docs/mref/P_System_Web_Script_Serialization_JavaScriptSerializer_MaxJsonLength.aspx

Thank you so much for your response...

Solve my problem perfect... Yes

Big Smile