Optional parameter in UriTemplate in WCF

Question

I've used the hint in this thread and provided a default value, so that when a user doesnät specify the virutal sub-directory, I'm making the assumption that he meant all the stuff to be listed. It works.

[OperationContract]
[WebInvoke(UriTemplate = "GetStuff/{type=all}", ...]
IEnumerable<Stuff> GetStuff(String type);

However, it would be nicer to specify a default value, instead. However, default(String) is null and I'd like to sent in an actual value. Particularly, I've set my heart on String.Empty. However, I noticed that the following doesn't work. The condition on server side doesn't recognize the empty string (...where 'type' in (ColName, '', 'all')).

[OperationContract]
[WebInvoke(UriTemplate = "GetStuff/{type=String.Empty}", ...]
IEnumerable<Stuff> GetStuff(String type);

What to do?

score 3 · Answer 1 · answered Aug 14 '14 at 11:19

It worked with "=null" for me. My contract looks like this:

[WebInvoke(UriTemplate = "UploadFile/{fileName}/{patientId}/{documentId}/{providerName=null}", Method = "POST")]

void UploadFile(string fileName, string patientId, string documentId, string providerName, Stream fileContents);

score 0 · Accepted Answer · answered Jun 22 '13 at 17:36

You can't really have an empty default value in an UriTemplate, but you can have something which will mean a default value, and at the operation you can replace that with the actual default value you want, as shown below.

public class StackOverflow_17251719
{
    const string DefaultValueMarker = "___DEFAULT_VALUE___";
    const string ActualDefaultValue = "";
    [ServiceContract]
    public class Service
    {
        [WebInvoke(UriTemplate = "GetStuff/{type=" + DefaultValueMarker + "}", ResponseFormat = WebMessageFormat.Json)]
        public IEnumerable<string> GetStuff(String type)
        {
            if (type == DefaultValueMarker)
            {
                type = ActualDefaultValue;
            }

            yield return type;
        }
    }
    public static void SendBodylessPostRequest(string uri)
    {
        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(uri);
        req.Method = "POST";
        req.ContentType = "application/json";
        req.GetRequestStream().Close(); // no request body

        HttpWebResponse resp;
        try
        {
            resp = (HttpWebResponse)req.GetResponse();
        }
        catch (WebException e)
        {
            resp = (HttpWebResponse)e.Response;
        }

        Console.WriteLine("HTTP/{0} {1} {2}", resp.ProtocolVersion, (int)resp.StatusCode, resp.StatusDescription);
        foreach (string headerName in resp.Headers.AllKeys)
        {
            Console.WriteLine("{0}: {1}", headerName, resp.Headers[headerName]);
        }

        Console.WriteLine();
        Stream respStream = resp.GetResponseStream();
        Console.WriteLine(new StreamReader(respStream).ReadToEnd());

        Console.WriteLine();
        Console.WriteLine("  *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*  ");
        Console.WriteLine();
    }
    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        WebServiceHost host = new WebServiceHost(typeof(Service), new Uri(baseAddress));
        host.Open();
        Console.WriteLine("Host opened");

        SendBodylessPostRequest(baseAddress + "/GetStuff/nonDefault");
        SendBodylessPostRequest(baseAddress + "/GetStuff");

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}

score 0 · Answer 3 · edited May 23 '17 at 11:50

0

You do have the ability to add an optional parameter to your URITemplate. However, it has to be the last parameter.

Optional UriTemplate parameter using WebGet

edited May 23 '17 at 11:50

Community

1
1

answered Sep 18 '15 at 22:17

Miles

113
7

Mahmoud Hboubati · Answer 4 · 2017-12-20T06:07:01.547

when adding only '=' to get a default value which is empty for string variable it throws the message

The UriTemplate '/applications/legal/statuses/{serviceId=}' is not valid; the UriTemplate variable declaration 'serviceId=' provides an empty default value to path variable 'serviceId'. Note that UriTemplate path variables cannot be bound to a null or empty value. See the documentation for UriTemplate for more details.

instead assign a default value and check later in the code:

 UriTemplate = "/applications/legal/statuses/{serviceId=default}"

service id will be default value.

Optional parameter in UriTemplate in WCF

4 Answers4

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