- Open visual studio command prompt.
- Use this command: dumpbin /headers C:\path\name.dll
- At the very beginning, you will find “FILE HEADER VALUES”, the first value will have a “(x86) ” for 32 bit and “(x64)” for 64 bit.
Tag: .Net
Using Response.Redirect in try…catch block
Using Response.Redirect in a try catch block in C#.Net will throw an exception “Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.”.
To work around use the overloaded method Response.Redirect(String url, bool endResponse) and pass false to second argument. The detailed reason can be found at http://support.microsoft.com/kb/312629/EN-US/.
REST Web Services calls with C#
It’s really easy to call REST based web services from C#.Net. Let’s see how to do it. We’ll be calling Yahoo Web Services as an example here.
Make REST Calls With C#
The .NET Framework provides classes for performing HTTP requests. This HOWTO describes how to perform both GET and POST requests.
Overview
The System.Net namespace contains the HttpWebRequest and HttpWebResponse classes which fetch data from web servers and HTTP based web services. Often you will also want to add a reference to System.Web which will give you access to the HttpUtility class that provides methods to HTML and URL encode and decode text strings.
Yahoo! Web Services return XML data. While some web services can also return the data in other formats, such as JSON and Serialized PHP, it is easiest to utilize XML since the .NET Framework has extensive support for reading and manipulating data in this format.
Simple GET Requests
The following example retrieves a web page and prints out the source.
C# GET SAMPLE 1
Simple POST Requests Some APIs require you to make POST requests. To accomplish this we change the request method and content type and then write the data into a stream that is sent with the request. C# POST SAMPLE 1
// We use the HttpUtility class from the System.Web namespace using System.Web; Uri address = new Uri("http://api.search.yahoo.com/ContentAnalysisService/V1/termExtraction"); // Create the web request HttpWebRequest request = WebRequest.Create(address) as HttpWebRequest; // Set type to POST request.Method = "POST"; request.ContentType = "application/x-www-form-urlencoded"; // Create the data we want to send string appId = "YahooDemo"; string context = "Italian sculptors and painters of the renaissance" + "favored the Virgin Mary for inspiration"; string query = "madonna"; StringBuilder data = new StringBuilder(); data.Append("appid=" + HttpUtility.UrlEncode(appId)); data.Append("&context=" + HttpUtility.UrlEncode(context)); data.Append("&query=" + HttpUtility.UrlEncode(query)); // Create a byte array of the data we want to send byte[] byteData = UTF8Encoding.UTF8.GetBytes(data.ToString()); // Set the content length in the request headers request.ContentLength = byteData.Length; // Write data using (Stream postStream = request.GetRequestStream()) { postStream.Write(byteData, 0, byteData.Length); } // Get response using (HttpWebResponse response = request.GetResponse() as HttpWebResponse) { // Get the response stream StreamReader reader = new StreamReader(response.GetResponseStream()); // Console application output Console.WriteLine(reader.ReadToEnd()); }
HTTP Authenticated requests
The del.icio.us API requires you to make authenticated requests, passing your del.icio.us username and password using HTTP authentication. This is easily accomplished by adding an instance ofNetworkCredentials to the request.
C# HTTP AUTHENTICATION
// Create the web request HttpWebRequest request = WebRequest.Create("https://api.del.icio.us/v1/posts/recent") as HttpWebRequest; // Add authentication to request request.Credentials = new NetworkCredential("username", "password"); // Get response using (HttpWebResponse response = request.GetResponse() as HttpWebResponse) { // Get the response stream StreamReader reader = new StreamReader(response.GetResponseStream()); // Console application output Console.WriteLine(reader.ReadToEnd()); }
Error Handling
Yahoo! offers many REST based web services but they don’t all use the same error handling. Some web services return status code 200 (OK) and a detailed error message in the returned XML data while others return a standard HTTP status code to indicate an error. Please read the documentation for the web services you are using to see what type of error response you should expect. Remember that HTTP Authentication is different from the Yahoo!Browser-Based Authentication.
Calling HttpRequest.GetResponse() will raise an exception if the server does not return the status code 200 (OK), the request times out or there is a network error. Redirects are, however, handled automatically.
Here is a more full featured sample method that prints the contents of a web page and has basic error handling for HTTP error codes.
C# GET SAMPLE 2
public static void PrintSource(Uri address) { HttpWebRequest request; HttpWebResponse response = null; StreamReader reader; StringBuilder sbSource; if (address == null) { throw new ArgumentNullException("address"); } try { // Create and initialize the web request request = WebRequest.Create(address) as HttpWebRequest; request.UserAgent = ".NET Sample"; request.KeepAlive = false; // Set timeout to 15 seconds request.Timeout = 15 * 1000; // Get response response = request.GetResponse() as HttpWebResponse; if (request.HaveResponse == true && response != null) { // Get the response stream reader = new StreamReader(response.GetResponseStream()); // Read it into a StringBuilder sbSource = new StringBuilder(reader.ReadToEnd()); // Console application output Console.WriteLine(sbSource.ToString()); } } catch (WebException wex) { // This exception will be raised if the server didn't return 200 - OK // Try to retrieve more information about the network error if (wex.Response != null) { using (HttpWebResponse errorResponse = (HttpWebResponse)wex.Response) { Console.WriteLine( "The server returned '{0}' with the status code {1} ({2:d}).", errorResponse.StatusDescription, errorResponse.StatusCode, errorResponse.StatusCode); } } } finally { if (response != null) { response.Close(); } } }
Further reading
Related information on the web.
XML with C#
There is excellent support for XML in Microsoft .Net framework, and there is a very good and easy article on it at Yahoo Developer Network.
I am pasting its content here for convenience. Enjoy 🙂
Using Returned XML with C#
Once you have retrieved data from a web service you will need to do something with it. This HOWTO describes the various built-in methods .NET provides to use XML returned by a web service.
- Overview
- Returned Data to a String
- Using XmlReader
- Using XmlDocument
- Using XPathNavigator/XPathDocument
- Using a DataSet
- Further Reading
Overview
The .NET Framework provides excellent support for XML. Combined with the data binding support of WinForms and ASP.NET applications you have an easy and powerful set of tools. ASP.NET 2.0 takes data binding another step further by providing the DataSource control which lets you declaratively provide data access to data-bound UI controls.
Returned Data to a String
The simplest way to view the returned data is to get the response stream and put it into a string. This is especially handy for debugging. The following code gets a web page and returns the contents as a string.
C# STRING SAMPLE
USING XMLREADER
XmlReader provides fast forward-only access to XML data. It also allows you to read data as simple-typed values rather than strings. XmlReader can load an XML document without having to use HttpRequest, though you won’t have the same amount of control over the request. If you use HttpRequest, you can just pass the stream returned by the GetResponseStream() method to XmlReader. Fast write-only functions are provided byXmlTextWriter.
With .NET 2.0 you should create XmlReader instances using the System.Xml.XmlReader.Create method. For the sake of compatibility and clarity the next sample uses the .NET 1.1 creation method.
C# XMLREADER SAMPLE
using System.Xml; // Retrieve XML document XmlTextReader reader = new XmlTextReader("http://xml.weather.yahoo.com/forecastrss?p=94704"); // Skip non-significant whitespace reader.WhitespaceHandling = WhitespaceHandling.Significant; // Read nodes one at a time while (reader.Read()) { // Print out info on node Console.WriteLine("{0}: {1}", reader.NodeType.ToString(), reader.Name); }
USING XMLDOCUMENT
XmlDocument gives more flexibility and is a good choice if you need to navigate or modify the data via the DOM. It also works as a source for the XslTransform class allowing you to perform XSL transformations.
C# XMLDOCUMENT SAMPLE
// Create a new XmlDocument XmlDocument doc = new XmlDocument(); // Load data doc.Load("http://xml.weather.yahoo.com/forecastrss?p=94704"); // Set up namespace manager for XPath XmlNamespaceManager ns = new XmlNamespaceManager(doc.NameTable); ns.AddNamespace("yweather", "http://xml.weather.yahoo.com/ns/rss/1.0"); // Get forecast with XPath XmlNodeList nodes = doc.SelectNodes("/rss/channel/item/yweather:forecast", ns); // You can also get elements based on their tag name and namespace, // though this isn't recommended //XmlNodeList nodes = doc.GetElementsByTagName("forecast", // "http://xml.weather.yahoo.com/ns/rss/1.0"); foreach(XmlNode node in nodes) { Console.WriteLine("{0}: {1}, {2}F - {3}F", node.Attributes["day"].InnerText, node.Attributes["text"].InnerText, node.Attributes["low"].InnerText, node.Attributes["high"].InnerText); }
Using XPathNavigator/XPathDocument
XPathDocument provides fast, read-only access to the contents of an XML document using XPath. Its usage is similar to using XPath with XmlDocument.
C# XPATHDOCUMENT SAMPLE
using System.Xml.XPath; // Create a new XmlDocument XPathDocument doc = new XPathDocument("http://xml.weather.yahoo.com/forecastrss?p=94704"); // Create navigator XPathNavigator navigator = doc.CreateNavigator(); // Set up namespace manager for XPath XmlNamespaceManager ns = new XmlNamespaceManager(navigator.NameTable); ns.AddNamespace("yweather", "http://xml.weather.yahoo.com/ns/rss/1.0"); // Get forecast with XPath XPathNodeIterator nodes = navigator.Select("/rss/channel/item/yweather:forecast", ns); while(nodes.MoveNext()) { XPathNavigator node = nodes.Current; Console.WriteLine("{0}: {1}, {2}F - {3}F", node.GetAttribute("day", ns.DefaultNamespace), node.GetAttribute("text", ns.DefaultNamespace), node.GetAttribute("low", ns.DefaultNamespace), node.GetAttribute("high", ns.DefaultNamespace)); }
Using a DataSet
Using a DataSet from the System.Data namespace lets you bind the returned data to controls and also access hierarchical data easily. A dataset can infer the structure automatically from XML, create corresponding tables and relationships between them and populate the tables just by calling ReadXml().
C# DATASET SAMPLE
using System.Data; public void RunSample() { // Create the web request HttpWebRequest request = WebRequest.Create("http://xml.weather.yahoo.com/forecastrss?p=94704") as HttpWebRequest; // Get response using (HttpWebResponse response = request.GetResponse() as HttpWebResponse) { // Load data into a dataset DataSet dsWeather = new DataSet(); dsWeather.ReadXml(response.GetResponseStream()); // Print dataset information PrintDataSet(dsWeather); } } public static void PrintDataSet(DataSet ds) { // Print out all tables and their columns foreach (DataTable table in ds.Tables) { Console.WriteLine("TABLE '{0}'", table.TableName); Console.WriteLine("Total # of rows: {0}", table.Rows.Count); Console.WriteLine("---------------------------------------------------------------"); foreach (DataColumn column in table.Columns) { Console.WriteLine("- {0} ({1})", column.ColumnName, column.DataType.ToString()); } // foreach column Console.WriteLine(System.Environment.NewLine); } // foreach table // Print out table relations foreach (DataRelation relation in ds.Relations) { Console.WriteLine("RELATION: {0}", relation.RelationName); Console.WriteLine("---------------------------------------------------------------"); Console.WriteLine("Parent: {0}", relation.ParentTable.TableName); Console.WriteLine("Child: {0}", relation.ChildTable.TableName); Console.WriteLine(System.Environment.NewLine); } // foreach relation }
Further reading
Related information on the web is listed below.
- XmlReader Class documentation
- XmlDocument Class documentation
- XPathDocument Class documentation
- Employing XML in the .NET Framework
- XML in .NET: .NET Framework XML Classes Offer Simple, Scalable Data Manipulation
- XML and the DataSet (.NET Framework Developer’s Guide)
- XML and SOAP Serialization (.NET Framework Developer’s Guide)
- XML Schema Definition Tool (Xsd.exe) (.NET Framework)