Specifying Queries Using REST

[This document supports a preliminary release of a software product that may be changed substantially prior to final commercial release. This document is provided for informational purposes only.]

As described in Specifying Queries Using REST or the Browser a GET request using REST interface can be sent to retrieve a single entity (authority, container or an entity) or submit a query to retrieve an entity set. The following C# sample illustrates both cases:

• The sample then creates WebRequest by passing a string that has a specific container URI followed by a query to retrieve all the entities in the container. The response in the case is an entity set.
• The response, <Entity> or <EntitySet> can be processed as needed. For illustration the example uploads the result in XmlDocument.

using System;
using System.Text;
using System.Net;
using System.Xml;
using System.IO;
using System.Xml.Linq;

namespace QueryUsingREST
{
    class Program
    {
        // Provide your data here
        private static string userName;
        private static string password;
        private const string authorityId = "<YourExistingAuthorityId>";
        private const string containerId = "<YourExistingContainerId>"; // that has the entity you want to retrieve
        private const string entityId = "<YourExistingEntityId>";

        private const string HttpGetMethod = "GET";
        private const string ssdsContentType = "application/x-ssds+xml";

        static void Main(string[] args)
        {
            Console.Write("Username: ");
            userName = Console.ReadLine();
            Console.Write("Password: ");
            password = ReadPassword();

            string entityUri = String.Format("https://{0}.data.database.windows.net/v1/{1}/{2}", authorityId, containerId, entityId);
            string query = String.Format("https://{0}.data.database.windows.net/v1/{1}?q='from e in entities select e'", authorityId, containerId);


            try
            {
                // GET entity 
                string data1 = GetResult(entityUri);
                // process the single entity returned. For example, you may load it in XmlDocument
                XmlDocument entityXml = new XmlDocument();
                entityXml.LoadXml(data1);
                // process the XmlDocument as you wish.

                // Query contianer
                string data2 = GetResult(query);
                // process the single entity returned. For example, you may load it in XmlDocument
                XmlDocument entitySetXml = new XmlDocument();
                entitySetXml.LoadXml(data2);
                // process the XmlDocument as you wish.

            }
            catch (WebException ex)
            {
                using (HttpWebResponse response = ex.Response as HttpWebResponse)
                {
                    if (response != null)
                    {
                        string errorMsg = ReadResponse(response);
                        Console.WriteLine("Error:{0}", errorMsg);
                        Console.WriteLine("Unexpected status code returned: {0}", response.StatusCode);
                    }
                    else
                    {
                        // Process DNS name resolution error
                        Console.WriteLine(ex.Message);
                    }
                }
            }
        }

        private static string GetResult(string entityUri)
        {
            string data = null;

            if (string.IsNullOrEmpty(entityUri))
            {
                throw new ArgumentOutOfRangeException("entityUri");
            }
            // retrieve
            WebRequest request = HttpWebRequest.Create(entityUri);
            request.Method = HttpGetMethod;
            //request.ContentLength = 0;
            request.ContentType = ssdsContentType;
            request.Credentials = new NetworkCredential(userName, password);

            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                data = ReadResponse(response);
                if (response.StatusCode != HttpStatusCode.OK)
                {
                    Console.WriteLine("Error: {0}", data);
                    Console.WriteLine("Unexpected status code returned: {0}", response.StatusCode);
                }
            }

            return data;
        }

        public static string ReadResponse(HttpWebResponse response)
        {
            // Begin by validating our inbound parameters.
            //
            if (response == null)
            {
                throw new ArgumentNullException("response", "Value cannot be null");
            }

            // Then, open up a reader to the response and read the contents to a string
            // and return that to the caller.
            //
            string responseBody = "";
            using (Stream rspStm = response.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(rspStm))
                {
                    responseBody = reader.ReadToEnd();
                }
            }

            return responseBody;
        }

        private static string ReadPassword()
        {
            StringBuilder retval = new StringBuilder();
            ConsoleKeyInfo keyInfo;
            while ((keyInfo = Console.ReadKey(true)).Key != ConsoleKey.Enter)
            {
                Console.Write("*");
                retval.Append(keyInfo.KeyChar);
            }
            Console.WriteLine();

            return retval.ToString();
        }
    }
}

See Also

Concepts

Specifying Queries Using REST or the Browser
Querying SQL Data Services