Cascading AJAX Dropdown list

Have you downloaded and installed ASP.Net AJAX yet? http://ajax.asp.net/

Yep.  I'm good to go on that.

You should be able to set up your SqlDataSource for the second control to accept the selected value of your first control as a parameter. ie "select name from models where make = @make" where @make is the selected value for the first dropdown.

I'm sorry, I didn't make myself clear enough.  I know how to populate another dropdown based on the value of the first drop down.  What I want to do is do it in a way where the whole ASP page doesn't have to be refreshed.  I've seen some examples, but most are in C#, I'm just curious if there is a VB.net example out there somewhere that can help me.  

Sorry for the confusion.

Carmodyk-

Check out this example from the ASP.NET AJAX AjaxControlToolkit:

http://ajax.asp.net/ajaxtoolkit/CascadingDropDown/CascadingDropDown.aspx

I think that illustrates exactly what you're after. Unfortunately, the source code for that demo is in C#. The C# code is very simple, though, and shouldn't be hard to convert to VB with an online tool. If you need help converting the C#, just let me know and I'll be happy to help.

Thanks~
Todd

Yes, I saw that, and it was very helpful as a starting point.  However, I got confused when it came to importing data from a SQL database.  (see following url: http://ajax.asp.net/ajaxtoolkit/Walkthrough/CCDWithDB.aspx)

If you follow the link, the part I got stuck on was this:

At runtime, the extender will make callbacks to a web service we specify (which is decorated with the Microsoft.Web.Script.Services.ScriptService attribute). In that web service, it expects a WebMethod with the following signature (note that parameter names must match too!):

What does that mean and what do I have to do to adjust to make this work from a database?

I'm sorry ChrisPont, but  this doesn't help me.  I tried to convert your code to VB.net using some of the converters out there, but no avail.  If you could explain the steps, I'm probably sure I can get this to work.  

Todd,  Thanks for the assistance, but I'm having multiple errors with your code.  First off, my program doesn't seem to like
Dim values As ListOf(AjaxControlToolkit.CascadingDropDownNameValue) =  New ListOf(AjaxControlToolkit.CascadingDropDownNameValue)

Currently, I'm getting "Method Error 12031"  What the heck is that!!!?!@

Carmodyk-

No idea. The AjaxControlToolkit.CascadingDrownDownValue is a type that comes with the AjaxControlToolkit (obviously). Make sure you have the AjaxControlToolkit assembly in your project's bin folder before using this code or your project won't know what to do with these types.

Remember, all the webservice is doing is returning a list of values from the server to the next drop down in the hierarchy based on the selected value. The only part of this example that you must implement is:

<WebMethod()> _
Public Function yourNameHere(ByVal knownCategoryValues As String, ByVal category As String) As AjaxControlToolkit.CascadingDropDownNameValue()

(Note the corrections I made to my original VB code). What you put in that function to build your CascadingDropDownNameValue list is completely up to you.

Thanks~
Todd

All right, I've got the errors to stop, but now I'm still having the same issues.  I'm getting a "Method Error 12031" still coming up and I can't seem to find any reference to it.  Any suggestions outside of using the Microsoft Toolkit example for cascading dropdown lists?

Sure! Did you say that you were open to 3rd party controls? If you are, there is a great example of this scenario using the r.a.d.combobox:

http://www.telerik.com/demos/aspnet/Combobox/Examples/Functionality/MultipleComboBoxes/DefaultVB.aspx

Not only is the example in VB, it does not require the complicated implementation of Web Services to work. Download the free trial of combobox here and give it a try:

http://www.telerik.com/products/aspnet/download.aspx

Let me know how that works for you. In the interest of transparency, I do work for Telerik, but hopefully our long discussion should make it evident that I am only interested in helping you find a working solution.

Thanks~
Todd

:)  I'm open to 3rd party controls, but not yet ready to shell out $800.00 just quite yet.  If everyone is willing to give up, so am I.

Give up?

Let's try this:

How Do I: Use the ASP.NET AJAX CascadingDropDown Control Extender? (27 min. video)
http://www.asp.net/learn/videos/view.aspx?tabid=63&id=77

VB source code -is- available with this demo here:
http://download.microsoft.com/download/f/7/a/f7adf2b4-6554-4027-bac6-c853bc0a4f9d/HDI-AJAX-CascadingDropDown-VB.zip

Maybe that will help answer the outstanding questions with the AjaxControlToolkit. Also, with regards to the Telerik controls, I can make them less than $800 for you if you are interested. I don't want to violate this site's advertising restrictions, so let me know if you're interested and we talk about this specific item offline.

Thanks~
Todd

Todd, thanks for all your input.  I was able to use the VB.code and manipulate the example using your insert, so I know it works.  Problem now is duplicating it.  In my duplication, I'm still getting the error messages.  Bah!

Thanks for the offer, I'll keep you in mind if I get any funds from work where I can purchase such things.  Right now, not so much.  :(

- Kevin

No problem. Good luck with the rest of your project.

Thanks~
Todd