.NET FOLLOWER

WebLoading Library: Downloading data from RESTful sources

July 23rd, 2012 Admin No comments

I often run into necessity to load data from sources published in the Internet. In most cases the sources are RESTful web-services, thus the data they emit is in xml or json formats. More and more web-services providers prefer spreading their data in an easier-to-use REST formats as a simpler alternative to SOAP and WSDL based web-services.

WebLoading Library Overview

For downloading data via the Http protocol I implemented a set of generic classes, let’s call it WebLoading Library. Almost every class in the library is a loader, which operates at a certain level of abstraction. The library allows to easily derive a new class from one of the exposed loaders, defining a type of the data to be loaded and the type of the ready-to-use data to be returned out of the loader. See the class diagram below.

I single out such basic steps of getting data as raw data loading, verification and conversion into a ready-to-use view. All loaders exposes the LoadData method aimed at performing these steps.The listing below demonstrates the LoadData‘s base implementation in the BaseLoader class. BaseLoader is a root base class for all loaders in the WebLoading Library hierarchy.

BaseLoader Source

using System;

namespace WebLoading
{
    /// <summary>
    /// Abstracts the data loading from a specified source. Provides such basic steps as data loading, verification and interpretation.
    /// </summary>
    /// <typeparam name="TRawData">A type of data to be loaded</typeparam>
    /// <typeparam name="TParsedData">A type of the analyzed data to be returned</typeparam>
    public abstract class BaseLoader<TRawData, TParsedData>
        where TRawData    : class
        where TParsedData : class
    {
        /// <summary>
        /// Loads data from a specified source, verifies it and returns its ready-to-use view.
        /// </summary>
        /// <returns>The ready-to-use view of the loaded data</returns>
        public virtual TParsedData LoadData()
        {
            TRawData rawData = LoadRawData();

            if (!IsRawDataValid(rawData))
                return default(TParsedData);
            
            TParsedData parsedData = ParseData(rawData);            

            return parsedData;
        }

        /// <summary>
        /// Loads data from a specified source. Has to be overridden in a derived class
        /// </summary>
        /// <returns>The loaded raw data</returns>
        protected abstract TRawData LoadRawData();

        /// <summary>
        /// Verifies the response retrieved from the specified source
        /// </summary>
        /// <param name="rawData">The raw data to be verified</param>
        /// <returns>True if the response is correct. Otherwise, False</returns>
        protected virtual bool IsRawDataValid(TRawData rawData)
        {
            return true;
        }       

        /// <summary>
        /// Analyzes the raw data and returns its ready-to-use view. Has to be overridden in a derived class
        /// </summary>
        /// <param name="rawData">The raw data</param>
        /// <returns>The ready-to-use view of the data</returns>
        protected abstract TParsedData ParseData(TRawData rawData);
    }
}

BaseLoader abstracts the loading from any source. Unlike BaseLoader, its direct descendant, HttpLoader, implies loading from a source supporting the Http protocol. See the listing of the HttpLoader class below.

HttpLoader Source

using System;
using System.Net;
using System.IO;

namespace WebLoading
{
    /// <summary>    
    /// Abstracts the data loading from a specified source using Http. Provides such basic steps as data loading, verification and interpretation.
    /// </summary>
    /// <typeparam name="TRawData">A type of data to be loaded</typeparam>
    /// <typeparam name="TParsedData">A type of the analyzed data to be returned</typeparam>
    public abstract class HttpLoader<TRawData, TParsedData> : BaseLoader<TRawData, TParsedData>
        where TRawData    : class
        where TParsedData : class
    {
        /// <summary>
        /// An initial url to load data from
        /// </summary>
        protected readonly string _requestUrl;

        /// <summary>
        /// Initializes a new instance of the HttpLoader class
        /// </summary>
        /// <param name="requestUrl">An initial url to load data from</param>
        public HttpLoader(string requestUrl)
        {
            _requestUrl = requestUrl;
        }

        /// <summary>
        /// Initializes a new instance of the HttpLoader class
        /// </summary>
        public HttpLoader()
        {            
        }

        /// <summary>       
        /// Loads data from a specified source using Http, returns a ready-to-analyze data view
        /// </summary>
        /// <returns>A ready-to-analyze view of the data</returns>
        protected override TRawData LoadRawData()
        {
            HttpWebRequest httpWebRequest = PrepareRequest();

            TRawData rawData;
            using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse())
                using (Stream responseStream = httpWebResponse.GetResponseStream())
                    rawData = ReadResponseStream(responseStream);

            return rawData;
        }

        /// <summary>
        /// Creates and initializes a Http request object
        /// </summary>
        /// <returns>A Http request object</returns>
        protected virtual HttpWebRequest PrepareRequest()
        {
            string url = PrepareUrl();

            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
            httpWebRequest.UserAgent      = @"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)";
            return httpWebRequest;
        }

        /// <summary>
        /// Prepares and returns an url the data should be loaded from. If the parameterless constructor is used, the method has to be overridden in a derived class
        /// </summary>
        /// <returns>An url to load the data from</returns>
        protected virtual string PrepareUrl()
        {
            return _requestUrl;
        }

        /// <summary>
        /// Reads from a stream and returns the received data in a ready-to-analyze view. Has to be overridden in a derived class
        /// </summary>
        /// <param name="stream">A data stream</param>
        /// <returns>The ready-to-analyze view of the data</returns>
        protected abstract TRawData ReadResponseStream(Stream stream);        
    }
}

The next level in the hierarchy comprises such loaders as ImageLoader, XmlLoader and JsonLoader. I’ll dwell upon the last two a bit later. As regards the first one, ImageLoader is a quite simple class derived from HttpLoader that downloads an image from a specified source via Http. Being initially intended for dealing with REST formats, the loaders family can be easily extended to any data formats. So, the ImageLoader is a good example to that. The class is shown below:

ImageLoader Source and How to use

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace WebLoading
{
    /// <summary>
    /// Downloads an image from a specified source using Http
    /// </summary>
    public class ImageLoader : HttpLoader<Image, Image>
    {
        /// <summary>
        /// Initializes a new instance of the ImageLoader class
        /// </summary>
        /// <param name="url">An url to load image from</param>
        public ImageLoader(string url) : base(url)
        {
        }

        /// <summary>
        /// Initializes a new instance of the ImageLoader class. Intended for use in a derived class
        /// </summary>
        protected ImageLoader()
        {
        }

        /// <summary>
        /// Reads an image from a stream
        /// </summary>
        /// <param name="stream">A data stream</param>
        /// <returns>An Image object</returns>
        protected override Image ReadResponseStream(Stream stream)
        {
            Image image = Image.FromStream(stream);
            return image;
        }

        /// <summary>
        /// Does nothing. Just returns a loaded image.
        /// </summary>
        /// <param name="rawData">The loaded image</param>
        /// <returns>The loaded image with no changes</returns>
        protected override Image ParseData(Image rawData)
        {
            return rawData;
        }
    }
}

//...
// "how to use" sample
ImageLoader imageLoader = new ImageLoader("http://dotnetfollower.com/wordpress/wp-content/uploads/2012/06/All_Site_Content_Links.png");
Image img = imageLoader.LoadData();

WebLoading Library Overview: XmlLoader

XmlLoader is an abstract class derived from HttpLoader and intended for xml data downloading. The downloaded raw xml is presented as a XDocument object. Create a descendent of the XmlLoader class to verify and turn the XDocument into any another desired view-object. The XmlLoader looks as follows:

XmlLoader Source

using System;
using System.IO;
using System.Xml.Linq;

namespace WebLoading
{
    /// <summary>    
    /// Abstracts the xml data loading from a specified source using Http. Provides such basic steps as data loading, verification and interpretation.
    /// </summary>
    /// <typeparam name="TParsedData">A type of the analyzed data to be returned</typeparam>
    public abstract class XmlLoader<TParsedData> : HttpLoader<XDocument, TParsedData> where TParsedData : class
    {
        /// <summary>
        /// Initializes a new instance of the XmlLoader class
        /// </summary>
        /// <param name="url">An initial url to load data from</param>
        public XmlLoader(string url) : base(url)
        {
        }

        /// <summary>
        /// Initializes a new instance of the XmlLoader class
        /// </summary>
        public XmlLoader()
        {
        }

        /// <summary>        
        /// Reads from a stream and returns the received xml data
        /// </summary>
        /// <param name="stream">A data stream</param>
        /// <returns>The received xml data</returns>
        protected override XDocument ReadResponseStream(Stream stream)
        {
            XDocument xDoc = XDocument.Load(stream);
            return xDoc;
        }
    }
}

As a simple example, below is a class-descendent demonstrating how to get the expected maximum temperatures for the next 7 days. The data source is http://graphical.weather.gov, which provides with xml data like the following:

Xml Data Sample

<?xml version="1.0"?>
<dwml version="1.0" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://graphical.weather.gov/xml/DWMLgen/schema/DWML.xsd">
  <head>
    <product srsName="WGS 1984" concise-name="time-series" operational-mode="official">
      <title>NOAA's National Weather Service Forecast Data</title>
      <field>meteorological</field>
      <category>forecast</category>
      <creation-date refresh-frequency="PT1H">2012-07-13T02:13:29Z</creation-date>
    </product>
    <source>
      <more-information>http://graphical.weather.gov/xml/</more-information>
      <production-center>Meteorological Development Laboratory<sub-center>Product Generation Branch</sub-center></production-center>
      <disclaimer>http://www.nws.noaa.gov/disclaimer.html</disclaimer>
      <credit>http://www.weather.gov/</credit>
      <credit-logo>http://www.weather.gov/images/xml_logo.gif</credit-logo>
      <feedback>http://www.weather.gov/feedback.php</feedback>
    </source>
  </head>
  <data>
    <location>
      <location-key>point1</location-key>
      <point latitude="28.50" longitude="-81.37"/>
    </location>
    <moreWeatherInformation applicable-location="point1">http://forecast.weather.gov/MapClick.php?textField1=28.50&amp;textField2=-81.37</moreWeatherInformation>
    <time-layout time-coordinate="local" summarization="none">
      <layout-key>k-p24h-n7-1</layout-key>
      <start-valid-time>2012-07-13T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-13T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-14T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-14T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-15T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-15T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-16T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-16T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-17T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-17T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-18T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-18T20:00:00-04:00</end-valid-time>
      <start-valid-time>2012-07-19T08:00:00-04:00</start-valid-time>
      <end-valid-time>2012-07-19T20:00:00-04:00</end-valid-time>
    </time-layout>
    <parameters applicable-location="point1">
      <temperature type="maximum" units="Fahrenheit" time-layout="k-p24h-n7-1">
        <name>Daily Maximum Temperature</name>
        <value>92</value>
        <value>93</value>
        <value>93</value>
        <value>94</value>
        <value>92</value>
        <value>94</value>
        <value>93</value>
      </temperature>
    </parameters>
  </data>
</dwml>

The GraphicalWeatherLoader class accepts a zip code of the region you need to get forecast for. See the next listing:

GraphicalWeatherLoader Source and How to use

using System;
using System.Collections.Generic;
using System.Xml.Linq;
using System.Xml.XPath;
using WebLoading;

namespace TestApp
{
    public class GraphicalWeatherLoader : XmlLoader<List<GraphicalWeatherLoader.DailyMaximumTemperature>>
    {
        public class DailyMaximumTemperature
        {
            public DateTime Day         { get; set; }
            public string   Temperature { get; set; }
        }

        protected static string _urlTemplate = "http://graphical.weather.gov/xml/SOAP_server/ndfdXMLclient.php?whichClient=NDFDgenMultiZipCode&lat=&lon=&listLatLon=&lat1=&lon1=&lat2=&lon2=&resolutionSub=&listLat1=&listLon1=&listLat2=&listLon2=&resolutionList=&endPoint1Lat=&endPoint1Lon=&endPoint2Lat=&endPoint2Lon=&listEndPoint1Lat=&listEndPoint1Lon=&listEndPoint2Lat=&listEndPoint2Lon=&zipCodeList={0}&listZipCodeList=&centerPointLat=&centerPointLon=&distanceLat=&distanceLon=&resolutionSquare=&listCenterPointLat=&listCenterPointLon=&listDistanceLat=&listDistanceLon=&listResolutionSquare=&citiesLevel=&listCitiesLevel=&sector=&gmlListLatLon=&featureType=&requestedTime=&startTime=&endTime=&compType=&propertyName=&product=time-series&begin=2004-01-01T00%3A00%3A00&end=2016-06-27T00%3A00%3A00&Unit=e&maxt=maxt&Submit=Submit";

        public GraphicalWeatherLoader(string zipCode) : base(string.Format(_urlTemplate, zipCode))
        {
        }

        protected override List<GraphicalWeatherLoader.DailyMaximumTemperature> ParseData(XDocument rawData)
        {
            List<DailyMaximumTemperature> res = new List<DailyMaximumTemperature>();

            XElement dataElement = rawData.XPathSelectElement("dwml/data");

            IEnumerator<XElement> dates        = dataElement.XPathSelectElements("time-layout/start-valid-time").GetEnumerator();
            IEnumerator<XElement> temperatures = dataElement.XPathSelectElements("parameters/temperature/value").GetEnumerator();
            
            while(dates.MoveNext() && temperatures.MoveNext())
            {
                DailyMaximumTemperature dailyMaximumTemperature = new DailyMaximumTemperature();
                dailyMaximumTemperature.Day         = DateTime.Parse(dates.Current.Value);
                dailyMaximumTemperature.Temperature = temperatures.Current.Value;
                res.Add(dailyMaximumTemperature);
            }            

            return res;
        }

        protected override bool IsRawDataValid(XDocument rawData)
        {
            string data = rawData.ToString();
            if(!string.IsNullOrWhiteSpace(data))
                return !data.Contains("SOAP ERROR");
            return false;
        }
    }
}

//...
// "how to use" sample
GraphicalWeatherLoader graphicalWeatherLoader = new GraphicalWeatherLoader("32801");
List<GraphicalWeatherLoader.DailyMaximumTemperature> temperatures = graphicalWeatherLoader.LoadData();
if (temperatures != null)
    foreach (GraphicalWeatherLoader.DailyMaximumTemperature temperature in temperatures)
        Console.WriteLine(string.Format("{0} - {1} Fahrenheit", temperature.Day.ToShortDateString(), temperature.Temperature));

WebLoading Library Overview: JsonLoader

Like XmlLoader, the JsonLoader class is abstract and derived from HttpLoader too. It’s dedicated for downloading json data. The downloaded json is processed by the JsonParser borrowed from the fastJSON project by Mehdi Gholam. Undoubtedly it’s the fastest json parser I’ve ever met. So, many thanks to Mehdi. The parsed json data is presented as a Dictionary<string, object>, which, besides simple objects, may contain arrays and other dictionaries nested on different levels. To have an ability to verify and transform the dictionary into something different, just create a descendent of the JsonLoader. Below is the listing of the JsonLoader:

JsonLoader Source

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using fastJSON;

namespace WebLoading
{
    /// <summary>    
    /// Abstracts the json data loading from a specified source using Http. Provides such basic steps as data loading, verification and interpretation.
    /// </summary>
    /// <typeparam name="TParsedData">A type of the analyzed data to be returned</typeparam>
    public abstract class JsonLoader<TParsedData> : HttpLoader<Dictionary<string, object>, TParsedData> where TParsedData : class
    {
        /// <summary>
        /// Initializes a new instance of the JsonLoader class
        /// </summary>
        /// <param name="url">An initial url to load data from</param>
        public JsonLoader(string url) : base(url)
        {
        }

        /// <summary>
        /// Initializes a new instance of the JsonLoader class
        /// </summary>
        public JsonLoader()
        {
        }

        /// <summary>        
        /// Reads json data from a stream and represents it as a tree of key-value collections
        /// </summary>
        /// <param name="stream">A data stream</param>
        /// <returns>A root key-value collection</returns>
        protected override Dictionary<string, object> ReadResponseStream(Stream stream)
        {
            StreamReader reader = new StreamReader(stream);
            string jsonText = reader.ReadToEnd();

            JsonParser parser = new JsonParser(jsonText, false);
            return parser.Decode() as Dictionary<string, object>;
        }

        /// <summary>
        /// Obtains object from a tree of key-value collections using a xpath-like path (for example, "set/items/item")
        /// </summary>
        /// <param name="dictionary">A root key-value collection</param>
        /// <param name="path">A xpath-like path</param>
        /// <returns>A found object</returns>
        protected static object SelectObject(Dictionary<string, object> dictionary, string path)
        {
            List<object> res = SelectObjects(dictionary, path, true, true);
            return res.Count > 0 ? res[0] : null;
        }

        /// <summary>
        /// Obtains object from a tree of key-value collections using a xpath-like path (for example, "set/items/item")
        /// </summary>
        /// <param name="dictionary">A root key-value collection</param>
        /// <param name="path">A xpath-like path</param>
        /// <param name="returnNull">Determines if nulls should be returned or skipped</param>
        /// <returns>A found object</returns>
        protected static List<object> SelectObjects(Dictionary<string, object> dictionary, string path, bool returnNull)
        {
            return SelectObjects(dictionary, path, returnNull, false);
        }

        /// <summary>
        /// Obtains object from a tree of key-value collections using a xpath-like path (for example, "set/items/item")
        /// </summary>
        /// <param name="dictionary">A root key-value collection</param>
        /// <param name="path">A xpath-like path</param>
        /// <param name="returnNull">Determines if nulls should be returned or skipped</param>
        /// <param name="onlyFirstFound">Determines if the search should be stopped after the first found object</param>
        /// <returns>A found object</returns>
        private static List<object> SelectObjects(Dictionary<string, object> dictionary, string path, bool returnNull, bool onlyFirstFound)
        {
            List<object> res = new List<object>();

            string[] pathPatterns = path.Split(new string[] { "/" }, StringSplitOptions.RemoveEmptyEntries);

            List<Dictionary<string, object>> dicts = new List<Dictionary<string, object>>() { dictionary };
            for (int i = 0; i < pathPatterns.Length; i++)
            {
                string pattern = pathPatterns[i];

                Dictionary<string, object>[] dictsToProcess = dicts.ToArray();
                dicts.Clear();

                foreach (Dictionary<string, object> currentDictionary in dictsToProcess)
                {
                    if (currentDictionary.ContainsKey(pattern))
                    {
                        object obj = currentDictionary[pattern];

                        if (i == pathPatterns.Length - 1) // is it last pattern
                        {
                            if (obj != null || returnNull)
                                res.Add(obj);
                        }
                        else // move forward
                        {
                            if (obj is Dictionary<string, object>)
                                dicts.Add(obj as Dictionary<string, object>);
                            else
                                if (obj is IEnumerable)
                                    foreach (object childObj in obj as IEnumerable)
                                        if (childObj is Dictionary<string, object>)
                                            dicts.Add(childObj as Dictionary<string, object>);
                        }
                    }

                    if (onlyFirstFound && res.Count > 0)
                        break;
                }

                if (dicts.Count == 0)
                    break;
            }

            return res;
        }
    }
}

Pay attention to the SelectObjects methods that obtain an specified object(s) from a tree of arrays and dictionaries using a xpath-like path (for example, “set/items/item”).

Let’s take a look at yet another example, this time it’s a descendent of JsonLoader. The derived class is quite pointless and just gets names of some capital-cities. The http://api.geonames.org service returns the json data in the following form:

Json Data Sample

{
   "geonames":[
      {
         "fcodeName":"capital of a political entity",
         "toponymName":"Mexico City",
         "countrycode":"MX",
         "fcl":"P",
         "fclName":"city, village,...",
         "name":"Mexiko-Stadt",
         "wikipedia":"",
         "lng":-99.12766456604,
         "fcode":"PPLC",
         "geonameId":3530597,
         "lat":19.428472427036,
         "population":12294193
      },
      {
         "fcodeName":"capital of a political entity",
         "toponymName":"Manila",
         "countrycode":"PH",
         "fcl":"P",
         "fclName":"city, village,...",
         "name":"Manila",
         "wikipedia":"",
         "lng":120.9822,
         "fcode":"PPLC",
         "geonameId":1701668,
         "lat":14.6042,
         "population":10444527
      },
      {
         "fcodeName":"capital of a political entity",
         "toponymName":"Dhaka",
         "countrycode":"BD",
         "fcl":"P",
         "fclName":"city, village,...",
         "name":"Dhaka",
         "wikipedia":"",
         "lng":90.40743827819824,
         "fcode":"PPLC",
         "geonameId":1185241,
         "lat":23.710395616597037,
         "population":10356500
      }
   ]
}

The next listing is the GeoNamesCitiesLoader class:

GeoNamesCitiesLoader Source and How to use

using System;
using System.Collections;
using System.Collections.Generic;
using WebLoading;

namespace TestApp
{
    public class GeoNamesCitiesLoader : JsonLoader<List<GeoNamesCitiesLoader.City>>
    {
        public class City
        {
            public string  FCodeName   { get; set; }
            public string  ToponymName { get; set; }
            public string  CountryCode { get; set; }
            public string  Name        { get; set; }
            public string  Wikipedia   { get; set; }
            public decimal Population  { get; set; }
            public double  Longitude   { get; set; }
            public double  Latitude    { get; set; }            
        }

        protected override bool IsRawDataValid(Dictionary<string, object> rawData)
        {
            return base.IsRawDataValid(rawData);
        }

        protected override string PrepareUrl()
        {
            return "http://api.geonames.org/citiesJSON?north=44.1&south=-9.9&east=-22.4&west=55.2&lang=de&username=demo";
        }

        protected override List<City> ParseData(Dictionary<string, object> rawData)
        {
            List<City> res = new List<City>();

            IEnumerable arrayOfDictionaries = SelectObject(rawData, "geonames") as IEnumerable;
            foreach (Dictionary<string, object> dict in arrayOfDictionaries)
                res.Add(CreateCity(dict));

            return res;
        }
       
        private City CreateCity(Dictionary<string, object> metadata)
        {
            City res = new City();

            foreach (KeyValuePair<string, object> pair in metadata)
            {
                switch (pair.Key.ToLower())
                {
                    case "fcodename":   res.FCodeName   = Convert.ToString(pair.Value);  break;
                    case "toponymname": res.ToponymName = Convert.ToString(pair.Value);  break;
                    case "countrycode": res.CountryCode = Convert.ToString(pair.Value);  break;
                    case "name":        res.Name        = Convert.ToString(pair.Value);  break;
                    case "wikipedia":   res.Wikipedia   = Convert.ToString(pair.Value);  break;
                    case "lng":         res.Longitude   = Convert.ToDouble(pair.Value);  break;
                    case "lat":         res.Latitude    = Convert.ToDouble(pair.Value);  break;
                    case "population":  res.Population  = Convert.ToDecimal(pair.Value); break;                    
                }
            }            

            return res;
        }
    }
}

//...
// "how to use" sample
GeoNamesCitiesLoader geoNamesCitiesLoader = new GeoNamesCitiesLoader();
List<GeoNamesCitiesLoader.City> cities = geoNamesCitiesLoader.LoadData();
if (cities != null)
    foreach (GeoNamesCitiesLoader.City city in cities)
        Console.WriteLine(string.Format("{0} [Population: {1}]", city.ToponymName, city.Population));

The source code and examples are available to download here.

Categories: C#, JSON, XML Tags: C#, JSON, XML

SharePoint: How To Maximize a Modal Dialog Window

July 17th, 2012 Admin No comments

In SharePoint 2010 by default a list item is opened in a Modal Dialog Window. The dialog adjusts its size depending on the size of the contained content and provides users with buttons to maximize and close itself. So, I was asked to maximize the dialog when opening some list items.

Creating and Initializing of a Modal Dialog Window

The JavaScript responsible for the dialog rendering is in the SP.UI.Dialog.js file (usually located in C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS). Clicking on a link-title, for example, in a list view leads to creating and displaying a new Modal Dialog Window in a manner similar to the following:

var options = SP.UI.$create_DialogOptions();

options.url           = 'display-page corresponding to the current list item';
options.title         = 'list item title';
options.allowMaximize = true;
options.showClose     = true;

// possible option, but it's not used in the place in question
//options.showMaximized = true;

var modalDialog = SP.UI.ModalDialog.showModalDialog(options);

The commented line demonstrates one of the possible settings, showMaximized, which apparently does exactly what we need. So, it would be a good solution if we had control under creation of the dialog. Unfortunately, we don’t have. Modifying scripts in SharePoint system js-files runs counter to all known “best practices”, therefore I don’t even consider it. Another possible way is override the client-side OnClick-events of the link-title fields everywhere (in list views, web parts and so on) so that your own script would create and display the dialog in a required manner. Obviously, it’s a very time-consuming solution. Moreover, every time when creating a list view, web part or something else you always have to keep in mind the possible need to rewrite their OnClick-events. In my opinion the only acceptable approach is allow a web page itself to maximize the dialog window it’s placed in.

Script to Maximize a Modal Dialog Window

For that, first of all, we need to have a JavaScript to maximize the current dialog. As SP.UI.Dialog.js doesn’t provide a function/method intended for use outside, we have to consume undocumented internal functions. A suitable script is described in the blog post – “How to maximize a Modal Dialog in JavaScript?“. With slight changes the JavaScript looks like the following

function _maximizeWindow() {
    var currentDialog = SP.UI.ModalDialog.get_childDialog();
    if (currentDialog != null && !currentDialog.$S_0)
        currentDialog.$z();    
    }
    ExecuteOrDelayUntilScriptLoaded(_maximizeWindow, 'sp.ui.dialog.js');

_maximizeWindow gets the current dialog window instance and tries to maximize it if it hasn’t been done before. ExecuteOrDelayUntilScriptLoaded, in turn, is applied to ensure the _maximizeWindow is called after the sp.ui.dialog.js has been completely loaded.

Script Applying

Having the script, we can insert it into the end of a web page to be maximized. It could be done through SharePoint Designer or by modifying a physical aspx-file defined as a display/new/edit form for a list or a content type. However, I decided to add the script dynamically in a page’s code-behind. So, the resultant code is shown below:

using System;
using System.Web.UI;
using Microsoft.SharePoint;

//...

public class DisplayListItem : Page
{
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        if(!IsPostBack)
            AddMaximizeWindowScript();
    }

    //...

    protected virtual void AddMaximizeWindowScript()
    {
        if (SPContext.Current.IsPopUI)
        {
            const string scriptKey = "MaxWinwScript";
            if (!ClientScript.IsClientScriptBlockRegistered(GetType(), scriptKey))
            {
                const string jsScript =
                    @"function _maximizeWindow() {
                        var currentDialog = SP.UI.ModalDialog.get_childDialog();
                        if (currentDialog != null && !currentDialog.$S_0)
                            currentDialog.$z();    
                        }
                        ExecuteOrDelayUntilScriptLoaded(_maximizeWindow, 'sp.ui.dialog.js');";

                ClientScript.RegisterClientScriptBlock(GetType(), scriptKey, jsScript, true);
            }
        }
    }
    
    //...
}

You may ask why I use RegisterClientScriptBlock instead of RegisterStartupScript or window.onload, or jQuery‘s $(document).ready (the latest two arise on client side). The reason is that initially the dialog window is created with the autoSize option. So, it’s very reasonable to maximize the window as soon as possible to prevent the content’s size calculating, which apparently happens after the page has been loaded entirely.

Categories: ASP.NET, JavaScript, Modal Dialog Window, SharePoint 2010 Tags: ASP.NET, JavaScript, Modal Dialog Window, SharePoint 2010

SharePoint: How to Delete a List Field/Column programmatically

July 13th, 2012 Admin No comments

Sometimes I need to remove a list field, which is not in use anymore. To remove the field we need just to call SPField.Delete method. However, there are situations when the field cannot be deleted due to some conditions, for example, when the field is read-only and etc. Because of that you might get such exceptions as

"The field cannot be deleted because it is a read only field in the list." "The field cannot be deleted because it is a sealed field in the list." "The field cannot be deleted because it is a hidden field in the list."

and other. So, let’s consider how these difficulties can be overcome (if it’s possible at all).

Inside the SPField.Delete method

The SPField.Delete does nothing except calling the Delete method of the SPFieldCollection class. The listing below demonstrates the short version of the SPFieldCollection.Delete:

public void Delete(string internalFieldName)
{
    SPField fld = ... // get the field from the current collection
    ...	

    if (!fld.CanBeDeleted)
        ... // throw an eception

    SPFieldLookup lookup = fld as SPFieldLookup;
    if (((lookup != null) && !lookup.IsDependentLookup) && (lookup.GetDependentLookupInternalNames().ToArray().Length != 0))
        ... // throw an eception     

    ... // delete the field
}

Where the CanBeDeleted property of the field defined as the following:

public bool CanBeDeleted
{
    get
    {
        if (this.AllowDeletion.HasValue)
            return this.AllowDeletion.Value;
        return (!this.FromBaseType && !this.Sealed);
    }
}

*Note: this code is true for both SharePoint 2007 and SharePoint 2010.

As we can see, deleting a list field, SharePoint explicitly analyzes such properties of the field as AllowDeletion, Sealed and FromBaseType. Additionally, experiments show that the ReadOnlyField and Hidden properties are being examined as well (likely it happens somewhere in the unmanaged SharePoint modules).

Workaround

An obvious workaround is, before calling SPField.Delete, change the above properties so that the field would be allowed for deletion. So, taking that into account, I implemented the following method(s) to delete list fields:

public static bool RemoveField(SPField spField)
{
    if (spField == null)
    {
        WriteErrorToLog("spField is null! Please, provide a valid one");
        return false;
    }

    bool res = false;
    try
    {
        // check if it's a ReadOnly field.
        // if so, reset it
        if (spField.ReadOnlyField)
        {
            spField.ReadOnlyField = false;
            spField.Update();
        }

        // check if it's a Hidden field.
        // if so, reset it
        if (spField.Hidden)
        {
            spField.Hidden = false;
            spField.Update();
        }

        // check if the AllowDeletion property is set to false.
        // if so, reset it to true
        if (spField.AllowDeletion == null || !spField.AllowDeletion.Value)
        {
            spField.AllowDeletion = true;
            spField.Update();
        }

        // If the AllowDeletion property is set, 
        // the Sealed property seems not to be examined at all.
        // So the following piece of code is commented.
        /*if(spField.Sealed)
        {
            spField.Sealed = false;
            spField.Update();
        }*/

        // If the AllowDeletion property is set, 
        // the FromBaseType property seems not to be examined at all.
        // So the following piece of code is commented.
        /*if(spField.FromBaseType)
        {
            spField.FromBaseType = false;
            spField.Update();
        }*/

        // finally, remove the field
        spField.Delete();
        spField.ParentList.Update();

        res = true;
    }
    catch (Exception ex)
    {
        WriteErrorToLog(ex.Message);
    }

    return res;
}

public static bool RemoveField(SPList spList, string displayNameOrInternalNameOrStaticName)
{
    SPField spField = GetFieldByName(spList, displayNameOrInternalNameOrStaticName);
    if(spField == null)
    {
        WriteErrorToLog(string.Format("Couldn't find field {0}!", displayNameOrInternalNameOrStaticName));
        return false;
    }

    return RemoveField(spField);
}

public static void WriteErrorToLog(string errorMsg)
{
    // write error into log
}

*Note: the GetFieldByName method is described here – Getting SPField with no exceptions to be thrown.

According to the code of the CanBeDeleted, the Sealed and FromBaseType properties are not being examined at all while the AllowDeletion is set. Thus the dealing with them is commented, but retained just in case.

Below is a sample of use:

SPSecurity.RunWithElevatedPrivileges(delegate
{
    using (SPSite spSite = new SPSite("some site url"))
        using (SPWeb spWeb = spSite.OpenWeb())
        {
            SPList spList = GetListByUrl(spWeb, "Lists/Products");
            RemoveField(spList, "product name");
        }
});

*Note: the GetListByUrl method is described here – Getting SPList with no exceptions to be thrown.

The RemoveField method isn’t a panacea. For example, you still will have problems if the field going to be deleted is a part of a multiple column lookup.

Be very careful when deleting fields, because it can lead to severe issues in your SharePoint applications. If you are uncertain, don’t delete anything, especially if it concerns a live application on a production server. Remember that you are always able to just make the field hidden instead.

Categories: Object Model, Share Point, SharePoint 2010 Tags: Object Model, Share Point, SharePoint 2010

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SharePoint: How To Maximize a Modal Dialog Window

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SharePoint: How to Delete a List Field/Column programmatically

Inside the SPField.Delete method

Workaround

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