I have also, in the last year and a half or so, been coding without MS Ajax. I have let go of things like the UpdatePanel and the Script Manager and have instead come to do direct Ajax calls to .ashx, default.aspx and web services. It feels that when you follow this approach that you have much tighter control over the quality of the UI. So what are your options for making Ajax calls in a .NET environment? I would like to think that there are a few options that stand out:

• Direct page ajax calls – you can use jQuery’s ajax function to call .ashx and .aspx pages. I have recently started using the [WebMethod] attribute in my .aspx files to make calls, and what I like about it is that you can tell the page to output JSON, which automatically serializes the method’s return type. I have also used ashx files to do ajax calls and this worked well
• SOAP-based web services – an approach I learned last year was to use a javascript soap parser to parse soap-based web services. These were mainly .asmx services. You can configure .asmx services to return JSON as well
• WCF-services can be configured for SOAP or JSON but also use a REST-like approach

What other options are there for .NET developers when making Ajax calls?

Before I go into identifying a few possible solutions I need to try and understand what my need is and what it is I want to achieve. I am going to be tackling various ASP.NET MVC projects within the next two to three months, and I cannot possibly see myself knowing where all the exceptions in my application will happen, or even try and code in such a way that all my try{}catch{} statements catch the correct exception. At the same time there is no excuse to overlook an exception if it happens more than once, you have to handle it. Having noticed how many exceptions a WCF service can throw I know for a fact that I cannot know all the exceptions beforehand either, so I need something, a tool that allows me to see the exceptions, and add it to my code so I can catch them. So the basic need is simple, have a mechanism in place that allows exceptions in my system to be caught.

You might be going, OMW you don’t log? Well I have been with several development teams and I can tell you that not a lot of development teams log system errors. And there is a host of other things they also don’t do, but that is not a part of this blog post.

I searched StackOverflow, and to me it seems there are a couple of choices available for logging in the .NET world:

• Log4Net, the popular Java port
• Enterprise Library from Microsoft
• NLog
• ELMAH for ASP.NET

Maybe I need to consider all the features offered and decide on the best alternative, which would be:

• Ease of installation
• Ease of getting to the exception logs

My intention is to start looking at each one of these this week, and make a decision by the end of the week.

• Byte
• Char
• Int16
• UInt16
• Int32
• UInt32
• Long
• ULong
• Short
• UShort
• Decimal
• Double
• Float
• SByte
• Single
• Boolean
• Int64
• UInt64

I enjoyed doing it anyway, and I’m trying to do small projects at night to keep me motivated.

	
	








			New Website Under Construction
		

		


	

And if I use this code to loop through the childnodes:

            HtmlDocument doc = new HtmlDocument();
            string s;
            StringBuilder builder = new StringBuilder();
            using (StreamReader reader = new StreamReader(@"C:\Documents and Settings\user\Desktop\fremus.net\index.htm"))
            {
                while ((s = reader.ReadLine()) != null)
                {
                    builder.AppendLine(s);
                }
            }
            doc.LoadHtml(builder.ToString());
            Console.WriteLine(doc.DocumentNode.ChildNodes.Count);
            foreach (HtmlNode node in doc.DocumentNode.ChildNodes)
            {
                Console.WriteLine(node.Name);
                foreach (HtmlNode childNode in node.ChildNodes)
                {
                    Console.WriteLine("\t\t" + childNode.Name);
                    foreach (HtmlNode grandChildNode in childNode.ChildNodes)
                    {
                        Console.WriteLine("\t\t\t" + grandChildNode.Name);
                    }
                }
            }

I get the following result in my command line window:

As you can see from the output the html node has a text node. The head node has a text node, and it has 9 childnodes including 5 #text nodes. The body node has a text node as well, and it has 7 childnodes, four being #text and the other three being div. So what is this #text node? If you read this article on the W3C site you will see that it states:

A common error in DOM processing is to expect an element node to contain text.

However, the text of an element node is stored in a text node.

On the same page it then gives an example using a title tag. If you do a Google on “html #text node“, you will see that the second result points to an article and if you read the bit on the nodes it seems that each #text node is a child. The #text nodes that appear in the body node seem to point to the text spaces after each div or each element inside the body node. If I change my code slightly:

                    Console.WriteLine("\t\t" + childNode.Name);
                    foreach (HtmlNode grandChildNode in childNode.ChildNodes)
                    {
                        Console.WriteLine("\t\t\t" + grandChildNode.Name);
                        Console.WriteLine("\t\t\t\t" + grandChildNode.HasChildNodes);
                    }

It tells me that the divs have child elements, but the #text nodes do not. Thus it seems for each ‘empty space’ inside a node there exists a #text node. If I amend the HTML from earlier like this:

	
	





Test

Then the footer div will have two text nodes, and the paragraph node will have a textnode. My issues yesterday had to do with the way IE rendered the HTML and that when I used HTMLAgility to parse it, the node counts weren’t the same. From the sample HTML I have given so far that difference is negligble, but I found that if I went to a site like this one and I saved the HTML from IE and Chrome into separate HTML files and I ran my code with that HTML, I got different node counts. Here are two screenshots that illustrate this:

The first screen is the html from the page saved from chrome and the second one is from ie. Notice the extra text nodes.

Why would I want to adopt WCF? Well there are the list of reasons found in articles on MSDN, one whitepaper can be found here, and of particular interest is the combination of technologies and the general idea that interoperability is the main goal. But these things are just a way of promoting the technology, and its not until you understand what it can do that you realise what it is you are dealing with. And to help you get to that point you need to work through an example, and I found that after I worked through the “Getting Started Tutorial” example, a light went on and I was like, “ok I get it”. Essentially a WCF service is made up of two key elements (there is a third as well) but in terms of C# code there are two key elements:
*An interface marked as a Service Contract using the ServiceContract attribute and with the methods marked as OperationContracts using an attribute with the same name
*A class that implements the methods in the interface

The third part of a WCF service is the configuration settings which can be found in a web.config/app.config’s system.servicemodel tag. Within the servicemodel section you define service behaviours as well as endpoints. One of the keys to understanding WCF is knowing that a service is defined by its endpoint, see it as a consumer. WCF can be consumed by client web apps, Silverlight apps and desktop apps. The endpoints themselves have configuration settings as well specifically relating to message sizes.

From the tutorial I was able to see that you can run a WCF service in a browser, without having IIS running. Thats something I need to think about but it does pose a few interesting questions. After I did the tutorial I wanted to do a simple REST service, and that took a few minutes but eventually got that sorted. StackOverflow was quite helpful and so was several articles on MSDN, with this one being the most helpful.

http://developer.yahoo.com/yap/guide/caja-support.html

You could then use System.Uri to get all the bits in the Uri like this:

            Uri url = new Uri("http://developer.yahoo.com/yap/guide/caja-support.html");

            string[] arrUri = url.Segments;
            var item = from u in arrUri
                       select u;

            foreach (string s in item)
            {
                Console.WriteLine(s);
            }

Something else I started doing or using yesterday is the ToList().ForEach delegate method. I noticed it in the LinqToTwitter api:

            var twitterTrends = from trends in tCtx.Trends
                                select trends;

            twitterTrends.ToList().ForEach(t =>
                Console.WriteLine(t.Query));

The ForEach works on a list as well, so if you take the same code I wrote earlier using a foreach loop for the Uri segments you can rewrite that as:

item.ToList().ForEach(s => Console.WriteLine(s));

The variable s is an anonymous type so it infers from the type what type it is. That is shorter code, not sure if its more efficient, but it sure looks nicer.

    getXMLHTTPPostObject: function(url, elementName, parameters) {
        if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
        }
        else if (window.ActiveXObject) {
            // code for IE6, IE5
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        else {
            alert("Your browser does not support XMLHTTP!");
        }
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4) {
                document.getElementById(elementName).innerHTML = xmlhttp.responseText;
            }
        }
        xmlhttp.open("POST", url, true);
        xmlhttp.send(parameters);
    }

I use this function to create an XMLHttpRequest object by passing it:

• the URL for the AJAX call
• an elementName to put the result of request in
• A parameter list

I then have a function like this:

    addPost: function() {
        objXMLHTTP.getXMLHTTPPostObject("url to handler", "categoryTemp", "postTitle=" + document.getElementById("txtPostTitle").value + "&blogpost=" + document.getElementById("txtBlogPost").value);
    }

The function gets the values of two HTML input elements and passes it as parameters. The parameters are then used in the POST HTTPMethod. My next challenge was to get the data in the generic handler (.ashx) so that I can process it. I also wanted to return the data from the ASHX file to see that its processed successfully. So in my handler I created this code:

        context.Response.ContentType = "text/plain";
        System.IO.Stream body = context.Request.InputStream;
        System.Text.Encoding encoding = context.Request.ContentEncoding;
        System.IO.StreamReader reader = new System.IO.StreamReader(body, encoding);
        //if (context.Request.ContentType != null)
        //{
        //    context.Response.Write("Client data content type " + context.Request.ContentType);
        //}
        string s = reader.ReadToEnd();
        string[] content = s.Split('&');
        for (int i = 0; i < content.Length; i++)
        {
            string[] fields = content[i].Split('=');
            context.Response.Write("
" + fields[0] + "

");
            context.Response.Write("
" + fields[1] + "

");
        }
        //context.Response.Write(s);
        body.Close();
        reader.Close();

I first create a class of type Stream that is instantiated through the Response.InputStream property, after which I set the content encoding for the response object. I then create a StreamReader instance and call its ReadToEnd method. After this I do some string manipulation and return the text back to the XMLHttpRequest object, which then writes the content to an HTML Element.

• Make an object IEnumerable and loop through the results
• Use the Single() method to return a single object only

Typically you may have a situation where you write some Linq-to-XML like this:

IEnumerable attrib = from att in elemInner.Attributes()
                                             where (string)att.Name.ToString() == "sectionName"
                                             select att;

To loop through the results you have to use a foreach loop like this:

foreach (XAttribute innerAttrib in attrib)
{
     builder.AppendLine("
" + innerAttrib.Value +"

");
}

If however you just wanted a single attribute result, you could write the same code like this:

 XAttribute attribDisplayStyle = (from att in elemInner.Attributes()
                                            where (string)att.Name.ToString() == "sectionName"
                                            select att).Single();

Then you only have a single XAttribute instance and you dont need a foreach loop:

attribDisplayStyle.Value;

You would apply the same logic to XElement as well.