Now usually to update other common properties of a List, like Title, etc., we can easily rely on CSOM. However, there’s no such provision for these two properties or any other exclusive properties of any other List. Here, we’ll be focussing on the Survey List only.So when the Client Object Model fails, turn to services. The service Lists.asmx, comprises of many methods related to Lists. One of the method is UpdateList. This method has the following definition:

[SoapDocumentMethodAttribute("http://schemas.microsoft.com/sharepoint/soap/UpdateList", RequestNamespace="http://schemas.microsoft.com/sharepoint/soap/", ResponseNamespace="http://schemas.microsoft.com/sharepoint/soap/", Use=SoapBindingUse.Literal, ParameterStyle=SoapParameterStyle.Wrapped)] 
public XmlNode UpdateList (
    string listName,
    XmlNode listProperties,
    XmlNode newFields,
    XmlNode updateFields,
    XmlNode deleteFields,
    string listVersion
)

The XmlNode parameter listProperties, is the one I’ll be focusing at. This will be in the format of a

XmlNode where we can update/modify the following properties:

AllowMultiResponses	TRUE to allow multiple responses to the survey.
Description	A string that contains the description for the list.
Direction	A string that contains LTR if the reading order is left-to-right, RTL if it is right-to-left, or None.
EnableAssignedToEmail	TRUE to enable assigned-to e-mail for the issues list.
EnableAttachments	TRUE to enable attachments to items in the list. Does not apply to document libraries.
EnableModeration	TRUE to enable Content Approval for the list.
EnableVersioning	TRUE to enable versioning for the list.
Hidden	TRUE to hide the list so that it does not appear on the Documents and Lists page, Quick Launch bar, Modify Site Content page, or Add Column page as an option for lookup fields.
MultipleDataList	TRUE to specify that the list in a Meeting Workspace site contains data for multiple meeting instances within the site.
Ordered	TRUE to specify that the option to allow users to reorder items in the list is available on the Edit View page for the list.
ShowUser	TRUE to specify that names of users are shown in the results of the survey.
Title	A string that contains the title of the list.

As you can see the two exclusive properties of the List Survey, ShowUser & AllowMultiResponses are present here which is exactly what we need. The other properties can also be updated using the CSOM so I won’t be using them here.

One important thing, this method simultaneously, also creates, updates, & deletes Fields/SiteColumns for the given List. However, if you don’t want to use them (as will be the case here) you can pass an empty string as parameters.

Following is the code sample to accomplish this task. The first part demonstrates how to construct the parameter, listProperties.

Desired Format
<List Title=”List_Name” Description=”List_Description” Direction=”LTR”/>

XmlDocument xmlDoc = new System.Xml.XmlDocument();
XmlNode ndProperties = xmlDoc.CreateNode(XmlNodeType.Element, "List", "");
XmlAttribute ndTitleAttrib = (XmlAttribute)xmlDoc.CreateNode(XmlNodeType.Attribute, "Title", "");
XmlAttribute ndDescriptionAttrib = (XmlAttribute)xmlDoc.CreateNode(XmlNodeType.Attribute, "Description", "");
XmlAttribute ndDirectionAttrib = (XmlAttribute)xmlDoc.CreateNode(XmlNodeType.Attribute, "Direction", "");
XmlAttribute ndMultiresponse = (XmlAttribute)xmlDoc.CreateNode(XmlNodeType.Attribute, "AllowMultiResponses", "");
XmlAttribute ndShowUser = (XmlAttribute)xmlDoc.CreateNode(XmlNodeType.Attribute, "ShowUser", "");

ndTitleAttrib.Value = "My Survey";
ndDescriptionAttrib.Value = "Allowing multiple responses for this Survey";
ndDirectionAttrib.Value = "LTR";
ndMultiresponse.Value = "TRUE";
ndShowUser.Value = "TRUE";

ndProperties.Attributes.Append(ndTitleAttrib);
ndProperties.Attributes.Append(ndDescriptionAttrib);
ndProperties.Attributes.Append(ndDirectionAttrib);
ndProperties.Attributes.Append(ndMultiresponse);
ndProperties.Attributes.Append(ndShowUser);

So basically we're creating the following node

<List Title="My Survey" Description="Allowing multiple responses for this Survey" Direction="LTR" AllowMultiResponses="TRUE" ShowUser="TRUE"/>

Finally, we’re going to use this parameter in the UpdateList method. The following code is a sample demonstration to call this method from the Lists.asmx service. Note that since this service is dependant on the site’s url, it will always vary from site to site. Hence we’re setting the url of the web service at runtime. One more thing, all the parameters that will be passed should be string i.e., the OuterXml property for XmlNode parameters.

string webServiceUrl = ctx.Web.Url + "/_vti_bin/Lists.asmx";

StringBuilder sbEnvelope = new StringBuilder();
sbEnvelope.Append("");
sbEnvelope.Append("");
sbEnvelope.Append(String.Format(
    "" +
        "" +
            "{0}" +
            "{1}" +
            "{2}" +
            "{3}" +
            "{4}" +
            "{5}" +
        "" +
    ""
    , id, ndProperties.OuterXml, String.Empty, String.Empty, String.Empty, version));
sbEnvelope.Append("");

HttpWebRequest req = (HttpWebRequest)WebRequest.Create(webServiceUrl);
req.Method = "POST";
req.ContentType = "text/xml; charset=\"utf-8\"";
req.Accept = "text/xml";
req.Headers.Add("SOAPAction", "\"http://schemas.microsoft.com/sharepoint/soap/UpdateList\"");
req.UserAgent = "FrontPage";
req.UseDefaultCredentials = false;

Uri targetSite = new Uri(ctx.Web.Url);
SharePointOnlineCredentials spCredentials = (SharePointOnlineCredentials)ctx.Credentials;
string authCookieValue = spCredentials.GetAuthenticationCookie(targetSite);
req.CookieContainer = new CookieContainer();
req.CookieContainer.Add(
    new Cookie("FedAuth",
        authCookieValue.TrimStart("SPOIDCRL=".ToCharArray()),
        String.Empty,
        targetSite.Authority));

using (IO.Stream stream = req.GetRequestStream())
{
    using (IO.StreamWriter writer = new IO.StreamWriter(stream))
    {
        writer.Write(sbEnvelope.ToString());
    }
}

WebResponse response = req.GetResponse();
using (IO.Stream responseStream = response.GetResponseStream())
{
    XmlDocument xDoc = new XmlDocument ();
    xDoc.Load(responseStream);

    if (xDoc.DocumentElement != null && xDoc.DocumentElement.InnerText.Length > 0)
    {
        Debug.WriteLine(String.Concat(DateTime.Now.ToShortTimeString(), " Response of the Survey List Update: ", xDoc.DocumentElement.InnerText));
    }
}

Here’s a screen-shot of the UpdateList method. You can view your site’s service at your site’s url + “_vti_bin/Lists.asmx”