Sometime ago I wrote an article in which I demonstrated how one can implement Google Suggest Functionality using AJAX.NET library. This article takes one step forward and shows how to improve the functionality and select the suggestions using the arrow keys. The article is also supplemented with code which is provided at the end of the article.
Introduction:
Sometime ago I wrote an article in which I demonstrated how one can implement Google Suggest Functionality using AJAX.NET library. This article takes one step forward and shows how to improve the functionality and select the suggestions using the arrow keys. The article is also supplemented with code which is provided at the end of the article.
Downloading the AJAX.NET Library:
First of all you need to download AJAX.NET library created by Michael Schwarz. Now that you have downloaded the library and made the reference to the dll in your project we can start with some dirty stuff.
If you are not familiar on how to use the AJAX.NET library than please visit my article AJAX IN ACTION in which I explained in detail how to get started with the library.
Implementing the Server Side Methods:
Let's start by implementing the server side methods. The server side methods will populate the collection with the data from the database. In this article I am using Northwind database which is installed as the default database for SQL SERVER 7 and SQL SERVER 2000 databases.
First thing I will do is to get the data from the database. Let's see how this can be done.
| private ArrayList PopulateArrayList()
{ ArrayList categoryNameList = new ArrayList(); string query = "SELECT CategoryName FROM Categories"; SqlConnection myConnection = new SqlConnection(ConnectionString); SqlCommand myCommand = new SqlCommand(query, myConnection); SqlDataReader dr = null; try { myConnection.Open(); dr = myCommand.ExecuteReader(); while (dr.Read()) { if (dr["CategoryName"] != null) { categoryNameList.Add((string)dr["CategoryName"]); } } } finally { dr.Close(); myCommand.Dispose(); myConnection.Close(); } return categoryNameList; }
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The code above demonstrated how you can populate an ArrayList with the CategoryName column from the Northwind Categories table.
Now let's see the method Search which searches the ArrayList for the word inputted by the user.
| [Ajax.AjaxMethod]
public string Search(string searchString) { string word = String.Empty; ArrayList wordList = new ArrayList(); wordList = PopulateArrayList(); /* You can put wordList in the Cache object to improve performance */ foreach (string str in wordList) { if (str.ToLower().StartsWith(searchString.ToLower()) && searchString != "") word += str + "<BR>"; } return word; } |
The method that you want to call from the client side is marked with [Ajax.AjaxMethod] attribute. First I populate the ArrayList and then loop through the list to search for the word. Each time I find the word that starts with the same alphabet which the user has input I concatenate the character to the word with the line break tag so that when they are displayed on the screen they are on different lines.
Client Side Methods:
All the magic happens in the client side code. There are many client side method and I will discuss some of the methods that are most important. You can download the source code files which includes the complete source code of the Auto-Suggest application. The method shown below SearchWord is the heart and soul of the application. In this method I trap all the key-press events which include the TAB key event and the arrow-key events.
| function SearchWord(pressevent,keyValue)
{ var charCode = (pressevent.which)? pressevent.which : (event.keyCode); // alert(charCode); // Send to the Server Side Method to get the string if(charCode >=65 && charCode <=90 || charCode >= 97 && charCode <=122) { AutoSuggest.Search(keyValue,SearchWord_CallBack); } // if the backspace key (8) is pressed and 48 is for the delete button else if(charCode == 8 || charCode == 48) { // Reset the count _highlightSuggestionIndex = -2; AutoSuggest.Search(keyValue,SearchWord_CallBack); } // when the down arrow key is pressed else if(charCode == 40) { if((_highlightSuggestionIndex+2) <= document.getElementById("Display").childNodes.length) { _highlightSuggestionIndex = _highlightSuggestionIndex + 2; } Highlight(_highlightSuggestionIndex); } // When the up arrow key is pressed else if(charCode == 38) { if((_highlightSuggestionIndex-2) >= 0) { _highlightSuggestionIndex = _highlightSuggestionIndex -2; } Highlight(_highlightSuggestionIndex); } }
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Another important method is the SearchWord_CallBack(response). This method gets the response back from the server side method named Search.
| function SearchWord_CallBack(response)
{ var word = response.value; if(response != null) { document.getElementById("Display").style.visibility = "visible"; document.getElementById("Display").innerHTML = word.substring(0,word.length - 4); } } |
There are several other methods which adds different functionality to the application. You can download the complete source code and view the code in detail.
One thing that I would like to see is to change the background color of the rows of the suggestion menu when the arrow keys are pressed. If you implement this functionality shoot me an email at [email protected] and I will append it to this article.
I hope you like this article, happy coding!