Category Archives: File System

Some of the tips for learning how to interact with the File System using ASP.NET

Uploading the files – HTML5 and jQuery way!

Download the Sample from Dropbox

Most of the websites are using HTML5 and jQuery plugins, to upload the files without the user to have to send a POST request to the server, which is not a likely way of uploading the files.

Old way of uploading files

In old days, people likes to create a simple HTML form, and assign the encytype to it, that would let them select a file and then they will click on the Submit button which would then take them to a new page, where they will be shown the message, “Your photos have been uploaded” – or an error message telling them that there was an error. This is a bit irritating and awkward, because the user uploaded more like 5 photos among with one got an error, and the remaining 4 were also discarded and the user was told after 2 minutes to upload the 4 photos only and not that one particular image. Sometimes, connection is lost and other stuff!

New ways of uploading the files

The web is changing, and there are a lot of new ways in which the user can upload the image or his any file to the server, without having him to submit the form as he did back in 90s.

Using the iframes

Well before the HTML5, people used hidden iframes to target the form to be uploaded from, the iframe is just another HTML document embedded in your main HTML document, that if even navigated to any other web page doesn’t trigger any navigation event in the main page. Which means that if the form is submitted through an iframe the main page the user stands on it never submitted. But he can still view the results and other associated data, such as form elements and the result window.

HTML5 and JavaScript

But these are also old now, JavaScript is strong enough to upload your files, and using HTML5 you can easily work you way with the validations of Files too. You can manage which file to upload and which one to reject. This option also minimizes the chances of error for any file that were triggered in the old methods and the user was informed of those errors after he uploaded all of the HTTP request data.

In JavaScript, we can shorten down the code for creating an Ajax request – An Ajax request is an asynchronous request to the server to get some resources from the server and display it in the web page without needing to reload the web page. This technology (Ajax) enables us, to get any data to the web server without having to use the POST requests and reload the web page for the new content, and similarly it also enables us to send any data to the server – such as files, images and other data – to the web server. This makes the uploading of the content an easy method.

jQuery code

In this blog post, I will be using jQuery – why? because I love jQuery, it is shorter in syntax and looks cool, but remember it is slower than pure JavaScript because it is just a library that runs over JavaScript but the difference is barely noticable – to send the Ajax requests to the server, along with the file data that we want to be uploaded.

The first stage is to create the HTML form that will be capturing any of the file that the user wants to upload to the server. For example, the following code would be an example of the HTML form that will accept the files from the user and contains a simple button from which he will upload the files – I know, button is old method, but in this method this button won’t perform the built-in function, it will be captured by JavaScript and the page will stay where it is all using the JavaScript watch the jQuery code for more on this section.

<form method="post" id="form" enctype="multipart/form-data">
  <input type="file" name="file" />
  <input type="submit" value="Upload" />
</form>

Above is the example for the form. Now once we will look into the jQuery code, we will be able to omit the enctype=”multipart/form-data” part too. Until then, this form is – as it stands – will accept a (single; multiple files are not allowed yet) file and the Upload button will be used to trigger the main function.

The following is the JavaScript (jQuery) code that will capture the event and send a request alongwith the file.

$(document).ready(function () {
   // On the document ready
   $('input[type=submit]').click(function () {
     // Before the request starts, show the 'Loading message...'
     $('.result').text('File is being uploaded...');
     event.preventDefault();
     // On the click even,
     var formData = new FormData($('#form')[0]);
       $.ajax({
           type: 'POST',
           processData: false,
           contentType: false,
           data: formData,
           success: function (data) {
              // The file was uploaded successfully...
              $('.result').text('File was uploaded.');
           },
           error: function (data) {
              // there was an error.
              $('.result').text('Whoops! There was an error in the request.');
           }
       });
    });
 });

.. in the above code, there is an element where the result is being rendered. That was like this,

<p class="result"></p>

.. in this element you will be showing the process that is currently going on.

  1. First of all – It will show a File is being uploaded… message in this paragraph.
  2. After the upload.
    If the file was uploaded, a success note will be shown otherwise an error message will be displayed to the user.

How will be button not submit the form by using a POST request? That is overridden by the code, in the second line inside the event handler. event.preventDefault(); in this code line, the default behaviour that will be triggered is overridden. Meaning that the page won’t be loaded again by a POST request, instead only that code will execute that we want – the Ajax code in the code block.

ASP.NET method to capture and make sure the request was having a File

You can use the following code of ASP.NET, that will make sure that the file is attached with the request, and then follow on to the Saving process and so on. For example this code,

files = Request.Files.Count;
if(files > 0) {
   // Files are sent!
   for (int i = 0; i < files; i++) {
      var file = Request.Files[i];
      // Got the image...
      string fileName = Path.GetFileName(file.FileName);
      // Save the file...
      file.SaveAs(Server.MapPath("~/" + fileName));
   }
}

Above code will work, for any image or any file type. There is no validation until now, you can attach your own validations depending on the Mime type or the size of the file that was attached the request.

Omitting the enctype

Oh well, I said that after the jQuery code I will explain how can you omit the enctype attribute – or if you even miss writing the enctype the result will be valid to upload the file – is that when you’re using the FormData object, to send the data, it make the form to behave as if the enctype of the form was set to the multipart/form-data (which is required to encode the files and tranfer them on HTTP). ‘

That is why, even if you miss this part and are using the FormData you will see that the images are being uploaded to the server.

Points of Interest

HTML5 and jQuery are widely used frameworks to upload the files using Ajax request to the web servers making it easier to control the file types to be uploaded, validating the maximum file size to be uploaded and some other particular validation can be handled easily on the client-side making it easier for the user to perform uploading tasks fastly.

FormData is an object that once used makes it easy to encode the files and other data as if the form’s enctype was set to the multipart/form-data. This is used (and is required) to upload files on the server through HTTP requests.

You can prevent any default method to be executed upon any element or control, using the JavaScript’s preventDefault() method.

Scanning file for particular string or character (Searching)

Last fews days ago, I saw a post on Stack Overflow in which the user wanted to search the file content. Although I didn’t answer that post because it was off-topic for that website. But, now I wanted to share the code for that particular action to the public.

I was working on this project since today morning and I finally came up with the code for that. Actually not only me, some other Helpfull fellows from the Stack Overflow community too. I had a problem in my code but the guys there helped me and made me move on to my right track. A warm thank to them.

Well the code was simple and small in size. Although it was a powerfull code. I used a simple File.txt file in the res folder and then the coding began. Here is the file content.

Ok, here is some text!

Actually this file is created to test the validity of the java application

Java is my favourite programming language. I can say that, because for my every tag

on Stack Overflow, I have no enough score. But for Java I have scored enough!

And I think I can score even more 🙂

Wish me luck!

Then I wrote the code to search this file for the character or a string the user would input. Definitely I would search for a String, not a character. Because character would always be present in the file somewhere.

The code is

package com.wordpress.thevsorganisation.java.find_words;

import java.io.*;
import java.util.Scanner;

public class Main {
   public static void main (String[] args) throws IOException {
   // Only write the output here!!!
   System.out.print("Write the character to be found in the File: ");
   Scanner sc = new Scanner(System.in);
   String character = sc.next();
   // Find the character
   System.out.println("Searching now...");
   getCharacterLocation(character);
   // Close the resource!
   sc.close();
 }
 
 // Get character and all other methods would be here...
 public static void getCharacterLocation (String character) throws IOException {
   System.out.println("File found...");
   File file = new File("res/File.txt");
   Scanner sc = new Scanner(file);
   int lineNumber = 0;
   int totalLines = 0;
   boolean found = false;
   // First get the total number of lines
   while(sc.hasNextLine()) {
   totalLines++;
   sc.nextLine();
   System.out.println("Line looping! For Total Lines variable.");
   }
   int[] lineNumbers = new int[totalLines];
   int lineIndex = 0;
   System.out.println("Searching in each line...");
   sc.close();
   sc = new Scanner(file);
   while(sc.hasNextLine()) {
     // Until the end
     /* Get each of the character, I mean string from
     * each of the line... */
     String characterInLine = sc.nextLine().toLowerCase();
     if(characterInLine.indexOf(character.toLowerCase()) != -1) {
       found = true;
     }
     lineNumber++;
     if(sc.hasNextLine())
       sc.nextLine();
     }
     System.out.println("Searching complete, showing results...");
     // All done! Now post that.
     if(found) {
       // Something found! :D
       System.out.print("'" + character + "' was found in the file!");
     } else {
       // Nope didn't found a fuck!
       System.out.println("Sorry, '" + character + "' didn't match any character in file  .");
     }
   sc.close();
 }
}

Share the code, and do remember to ask for more!