Calling a WebMethod using jQueryAjax change casing - asp.net

Question

I have the following request using ajax (simplified):
<asp:TextBox ID="DealNumber" runat="server" Width="100px" ToolTip="Deal (aka OPG)">
</asp:TextBox>
<Ajax:AutoCompleteExtender
ID="AutoCompleteExtender2"
runat="server"
TargetControlID="DealNumber"
ServiceMethod="GetDealNumberList"
ServicePath="/ws/WebServices.asmx"/>
and on /ws/WebServices.asmx (sorry my .VB):
<System.Web.Script.Services.ScriptMethod(UseHttpGet:=True)>
<System.Web.Services.WebMethod>
Public Function GetDealNumberList(prefixText As String, count As Integer, contextKey As String) As System.String()
return {"Test " & PrefixText & " " & ContextKey}
end function
Now, doing the typical F12 network trace, ajax reports:
Invalid method name 'getdealnumberlist', method names are case sensitive. The method name 'GetWTNumberList' with the same name but different casing was found.
Who and why the casing is changed? If I modify my .asmx works as intended.

Answer 1

Not sure what exactly causing the problem, but I experienced this issue long time ago while still using webforms page and AJAX callback to return something from web service (ASMX). I fixed this issue by putting MessageName property with method name in lowercase inside WebMethodAttribute like this example:
<ScriptMethod(UseHttpGet:=True)>
<WebMethod(MessageName:="getdealnumberlist")>
Public Function GetDealNumberList(prefixText As String, count As Integer, contextKey As String) As String()
Return {"Test " & PrefixText & " " & ContextKey}
End Function
This problem also sometimes occurred when the web service methods are tested directly, e.g. by entering URL like http://localhost:XXXX/path/to/webservicename.asmx/GetDealNumberList.

Answer 2

In this annoying issue, I found the answer and it was very trivial.
In Visual Studio, when using Option Compare Binary Option Compare Text I was under the impression that will only affect code generation. I was wrong. Not sure what is the method to create the intermediate code for Web Services and/or AJAX, but, adding Option Compare Text fix the camel issue.
I personally think this is a (survivable) bug.