Simple SOAP call to update the status of a Microsoft CRM 2011 entity. The organization service Url can be found by going into Microsoft CRM -> Customizations -> Developer Resources

gistfile1.cs

        
        public void MakeTestAppointmentUpdate()
        {

            string serviceUrl = "<your organization service endpoint>/web";
            string userName = "username";
            string password = "password";
            string logicalEntityName = "appointment";                       
            string activityId = "ba9f21c5-82ac-e411-95dc-005056be7c4c";

            int stateCode = 1;
            int statusCode = 3;

            try
            {

                using (HttpClientHandler handler = new HttpClientHandler())
                {

                    handler.Credentials = new System.Net.NetworkCredential(userName, password);

                    using (HttpClient httpClient = new HttpClient(handler))
                    {

                        Uri uri = new Uri(serviceUrl);

                        httpClient.DefaultRequestHeaders.Accept.Clear();
                        httpClient.DefaultRequestHeaders.Add("Accept", "application/xml, text/xml, */*");
                        httpClient.DefaultRequestHeaders.Add("SOAPAction",
                            "http://schemas.microsoft.com/xrm/2011/Contracts/Services/IOrganizationService/Execute");


                        StringContent content =
                            new StringContent(CreateSoapPayload(logicalEntityName, activityId, stateCode, statusCode));

                        content.Headers.ContentType = MediaTypeHeaderValue.Parse("text/xml; charset=utf-8");

                        var response = httpClient.PostAsync(uri, content).Result;

                        System.Diagnostics.Debug.WriteLine(response.StatusCode);

                    }
                }
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(ex.Message);
                throw;
            }

        }
        
        /// <summary>
        /// Creates a Soap Payload for updating a given entity state
        /// <note>
        ///     The state and status code go hand in hand.  Please see the link below for the different codes
        ///     http://mostlymscrm.blogspot.co.uk/2012/06/entity-statecodes-and-statuscodes.html#!/2012/06/entity-statecodes-and-statuscodes.html
        /// </note>
        /// </summary>
        /// <param name="entityLogicalName">The logical name - i.e. appointment</param>
        /// <param name="activityId">The GUID activity Id (which we're keeping as a string)</param>
        /// <param name="stateCode">The state code</param>
        /// <param name="statusCode">The status code</param>
        /// <returns></returns>
        private string CreateSoapPayload(string entityLogicalName, string activityId, int stateCode, int statusCode)
        {
            StringBuilder sb = new StringBuilder();
            sb.AppendLine("<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\">");
            sb.AppendLine("<s:Body>");
            sb.AppendLine("<Execute xmlns=\"http://schemas.microsoft.com/xrm/2011/Contracts/Services\" xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\">");
            sb.AppendLine("<request i:type=\"b:SetStateRequest\" xmlns:a=\"http://schemas.microsoft.com/xrm/2011/Contracts\" xmlns:b=\"http://schemas.microsoft.com/crm/2011/Contracts\">");
            sb.AppendLine("<a:Parameters xmlns:c=\"http://schemas.datacontract.org/2004/07/System.Collections.Generic\">");
            sb.AppendLine("<a:KeyValuePairOfstringanyType>");
            sb.AppendLine("<c:key>EntityMoniker</c:key>");
            sb.AppendLine("<c:value i:type=\"a:EntityReference\">");
            sb.AppendLine("<a:Id>" + activityId + "</a:Id>");
            sb.AppendLine("<a:LogicalName>" + entityLogicalName + "</a:LogicalName>");        // appointment //
            sb.AppendLine("<a:Name i:nil=\"true\" />");
            sb.AppendLine("</c:value>");
            sb.AppendLine("</a:KeyValuePairOfstringanyType>");
            sb.AppendLine("<a:KeyValuePairOfstringanyType>");
            sb.AppendLine("<c:key>State</c:key>");
            sb.AppendLine("<c:value i:type=\"a:OptionSetValue\">");
            sb.AppendLine("<a:Value>" + stateCode + "</a:Value>");
            sb.AppendLine("</c:value>");
            sb.AppendLine("</a:KeyValuePairOfstringanyType>");
            sb.AppendLine("<a:KeyValuePairOfstringanyType>");
            sb.AppendLine("<c:key>Status</c:key>");
            sb.AppendLine("<c:value i:type=\"a:OptionSetValue\">");
            sb.AppendLine("<a:Value>" + statusCode + "</a:Value>");
            sb.AppendLine("</c:value>");
            sb.AppendLine("</a:KeyValuePairOfstringanyType>");
            sb.AppendLine("</a:Parameters>");
            sb.AppendLine("<a:RequestId i:nil=\"true\" />");
            sb.AppendLine("<a:RequestName>SetState</a:RequestName>");
            sb.AppendLine("</request>");
            sb.AppendLine("</Execute>");
            sb.AppendLine("</s:Body>");
            sb.AppendLine("</s:Envelope>");

            return sb.ToString();
        }