Reading JSON data from a webservice

Create a class for the JSON data

public class JSONData

{

public string id{ get; set; }

public string name{ get; set; }

}

Use this to consume the webservice

string requestURL = "Webservice URL";

CredentialCache credCache = new CredentialCache();

credCache.Add(new Uri(requestURL), "NTLM", CredentialCache.DefaultNetworkCredentials);

HttpWebRequest spRequest = (HttpWebRequest)HttpWebRequest.Create(requestURL);

spRequest.Credentials = credCache;

spRequest.UserAgent = "Mozilla/4.0+(compatible;+MSIE+5.01;+Windows+NT+5.0";

spRequest.Method = "GET";

spRequest.Accept = "application/json;odata=verbose";

HttpWebResponse endpointResponse = (HttpWebResponse)spRequest.GetResponse();

if (endpointResponse.StatusCode == HttpStatusCode.OK)

{

                using (endpointResponse)

{

using (var reader = new StreamReader(endpointResponse.GetResponseStream()))

{

JavaScriptSerializer serializer = new JavaScriptSerializer();

try

{

string jSON = reader.ReadToEnd();

JSONData data = new JavaScriptSerializer().Deserialize<JSONData>(jSON);

string strId = data.id;

string strName=data.name;

}

catch (Exception ex)

{

throw ex;

}

}

}

}

Check item exists based on a column value using REST API

<script type="text/javascript">
function PreSaveAction() {
var result = false;
var value=$("select[title=MyColumn] option:selected").text();
var requestUri = _spPageContextInfo.webAbsoluteUrl + "/_api/Web/Lists/getbytitle('MyList')/Items?$select=LinkTitle,MyColumn/Title&$expand=MyColumn&$filter=MyColumn/Title eq '" + value;
$.ajax
({
url: requestUri,
type: "GET",
cache: true,
async: false,
headers:{
"ACCEPT": "application/json;odata=verbose"
        },
success: function (data) {
if($(data.d.results).length == 0)
result = true;
else
alert("Retry!!!");
},
error: function () {
}
});
return result;
}
</script>