Proper DateTime Format for a Web Service

Question

I have a webservice with a method which is called via a xmlhttprequest object in my javascript. The method accepts a datetime parameter which is subsequently converted to a string and run against the database to perform a calculation.

I get the value from m_txtDateAdd and send off the xmlHttprequest

<asp:textbox id=m_txtDateAdd tabIndex=4 runat="server" Width="96px" Text="<%# Today %>">
</asp:textbox>

which has a validator attacted to it

<asp:CustomValidator id="m_DateAddValidator" runat="server" ErrorMessage="Please Enter a Valid Date" ControlToValidate="m_txtDateAdd">&#x25CF;</asp:CustomValidator>

My webmethod looks something like this

[WebMethod]
public decimal GetTotalCost(DateTime transactionDate)
{
    String sqlDateString = transactionDate.Year+"/"+transactionDate.Month+"/"+transactionDate.Day;

I use sqlDateString as part of the commandtext i send off to the database. Its a legacy application and its inline sql so I don't have the freedom to set up a stored procedure and create and assign parameters in my code behind. This works 90% of the time. The webservice is called on the onchange event of m_txtDateAdd. Every now and again the response i get from the server is

System.ArgumentException: Cannot convert 25/06/2009 to System.DateTime. System.ArgumentException: Cannot convert 25/06/2009 to System.DateTime.

Parameter name: type ---> System.FormatException: String was not recognized as a valid DateTime.

   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
   at System.DateTime.Parse(String s, IFormatProvider provider)
   at System.Convert.ToDateTime(String value, IFormatProvider provider)
   at System.String.System.IConvertible.ToDateTime(IFormatProvider provider)
   at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
   at System.Web.Services.Protocols.ScalarFormatter.FromString(String value, Type type)
   --- End of inner exception stack trace ---
   at System.Web.Services.Protocols.ScalarFormatter.FromString(String value, Type type)
   at System.Web.Services.Protocols.ValueCollectionParameterReader.Read(NameValueCollection collection)
   at System.Web.Services.Protocols.HtmlFormParameterReader.Read(HttpRequest request)
   at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters()
   at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()

Answer 1

You need to send a DateTime in the correct format for XML: 2009-07-10T12:40Z. From http://en.wikipedia.org/wiki/ISO_8601.

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Also, why are you using HttpRequest? Why not just use Add Service Reference?

Answer 2

How are you creating the DateTime to pass into GetTotalCost()?

Have you got the correct constructor overload from http://msdn.microsoft.com/en-us/library/system.datetime.aspx?

Answer 3

Are you passing the String value from the text box directly to the webservice? It would be more reliable to parse the user input String into a javascript Date object, pass the Date object to the webservice, and let the serializer in Microsoft's ajax library figure out how to format it.

It may be helpful to see the client side javascript code that is getting the value and calling the web service.