File Handling In SilverLight

In real time programming I have yet to see any application which does not need to work with files in one or the other way. Every programming Language gives a way to handle files, and so does Silverlight. Here we are going to discuss about the techniques, or I should say, the methods we can follow for handling files.

In My Previous Article we saw how we can increase our application's Isolated Area. How can we handle the files in the Isolated storage area. By File Handling I mean The Following :

1.Creating Files
2.Reading Files
3.Getting List of Files
4.Uploading The Existing Files to the Isolated Area.
5.Deleting Files

So let's get started. First we need a Silverlight application, and then we can add the controls and code to take care of the above functions.

 

1. Create FileUploadSLApp

Create a new Silverlight Application I am naming it as "FileUploadSLApp". And leave the other settings as it is.

 

2. Create Usercontrol

We can use MainPage.xaml or can create our own silverlight user control (.xaml). For this example I am going with the MainPage.xaml. The Usercontrol of the Mainpage.xaml will look like:
 

<UserControl x:Class="FileUploadSLApp.MainPage"
                      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
                      mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480"
                      Width="400" Height="300">
                      <Grid x:Name="LayoutRoot" Background="White">
                      <Canvas Canvas.Left="10" Canvas.Top="10"> 
                      <Button Content="Upload" Height="20" Click="Button_Click_1" Margin="10,60,162,54" VerticalAlignment="Bottom" d:LayoutOverrides="Width, Height" HorizontalAlignment="Right" Background="#FF2770AF"></Button>
                      <TextBox Text="Write File Name with Extention" Margin="10,10,0,0" x:Name="txtFileName"></TextBox>
                      <Button Content="Read Eile" Height="20" Click="Button_Click" Margin="65,60,162,54" VerticalAlignment="Bottom" d:LayoutOverrides="Width, Height" HorizontalAlignment="Right" Background="#FF2770AF"></Button>
                      <Button Content="Get List" Height="20" Click="Button_Click_2" Margin="130,60,162,54" VerticalAlignment="Bottom" d:LayoutOverrides="Width, Height" HorizontalAlignment="Right" Background="#FF2770AF"></Button>
                      <Button x:Name="btnDelete" Height="20" Margin="190,60,251,8" Content="Delete File" Click="btnDelete_Click"/>
                      <Button x:Name="btnWrite" Height="20" Margin="270,60,36,8" Content="Write" Click="btnWrite_Click" />
                      <TextBlock Height="20" Margin="10,100,126,79" VerticalAlignment="Bottom" Text="Select File to uload" TextWrapping="Wrap" FontSize="16" x:Name="txtStatus"/>
                      <TextBox Text="Enter The File Contents here......" Margin="10,140,0,0" x:Name="txtContent"></TextBox>
                      </Canvas>
                      </Grid>
                      </UserControl>

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The Page will Look like
 
 

3. Create File

In this section we will create a text file in the isolated storage area with the name as given by the user in te textbox. First we will check whether the file exist in the isolated storage area or not. If it does exist then we will create a new file with the name and if it exists then we will append the contents at the start of the file which user inputs in the textbox.

Now let us create the event handler for the button and navigate to the event.

 

private void btnWrite_Click(object sender, RoutedEventArgs e)
                      {
                          using (var MyAppStore = IsolatedStorageFile.GetUserStoreForApplication())
                          {
                              if (!(MyAppStore.FileExists(txtFileName.Text)))
                              {
                                  MessageBox.Show("File does not exist , we are creating one for you ");
                                  IsolatedStorageFileStream file = MyAppStore.CreateFile(txtFileName.Text);
                                  file.Close();
                              }
                              using (StreamWriter sw = new StreamWriter(MyAppStore.OpenFile(txtFileName.Text, FileMode.Open, FileAccess.Write)))
                              {
                                  sw.WriteLine(txtContent.Text);
                              }
                              txtContent.Text = "";
                              txtFileName.Text = "";
                              MessageBox.Show("File Writen");
                          }
                      } 

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4. Reading Files

This section of the article shows that how can we read a text file from the Isolated storage area of the application. We have Already created a button and the event handler for this in the .xaml file so let us navigate to the event and code there

 

private void Button_Click(object sender, RoutedEventArgs e)
                      {
                          //craeing a new link to the Application store for reading file in IsolatedStorage
                          using (var MyAppStore = IsolatedStorageFile.GetUserStoreForApplication())
                          {
                              //checking the existance of the file
                              if (!(MyAppStore.FileExists(txtFileName.Text)))
                              {
                                  //if doesnot exist prompt the user 
                                  MessageBox.Show("File does not exist ");
                                  //Clear the text from the textbox
                                  txtFileName.Text = string.Empty;
                              }
                              //if file does exist
                              else
                              {
                                  //create a stream reader to read the file
                                  using (StreamReader sr = new StreamReader(MyAppStore.OpenFile(txtFileName.Text, FileMode.Open, FileAccess.ReadWrite)))
                                  {
                                      //read file till end and post the contenst in hte textblock
                                      txtStatus.Text = sr.ReadToEnd();
                                  }
                              }
                          }
                      } 

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5. Getting List of Files from the Isolated Storage

In this section we will get the list file in the isolated storage area and Display it in the TextBlock. for Directory Handling please read next article Now navigating to the event handler

 

private void Button_Click_2(object sender, RoutedEventArgs e)
                      {
                          //clearing the textblockstatus to ensure that it is not having any text
                          txtStatus.Text = string.Empty;
                          //getting the handler for the isolated store
                          using (var MyAppStore = IsolatedStorageFile.GetUserStoreForApplication())
                          {
                              //holding the array (list) of file names into a string array
                              string[] str = MyAppStore.GetFileNames();
                              //creating a foreach loop to go through each elemen of the array
                              foreach (string s in str)
                              {
                                  //printing the filename in the textblock with a new line.
                                  txtStatus.Text = txtStatus.Text + Environment.NewLine + s;
                              }
                          }
                      } 

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6. Uploading File

In this section we will upload any file in the isolated storage area. and then access it from there for future use.

 

private void Button_Click_1(object sender, RoutedEventArgs e)
                      {
                          //creating the refrence for the dialog
                          OpenFileDialog dlg = new OpenFileDialog();
                          //creating the filter for the dialog
                          dlg.Filter = "All files (*.*)|*.*";
                          //Displaying the Dialog box remeber this should be user itnitated.
                          if (dlg.ShowDialog() == true)
                          {
                              txtStatus.Text = "Uploading Files ";
                              // Save all selected files into application's isolated storage 
                              IsolatedStorageFile iso = IsolatedStorageFile.GetUserStoreForApplication();
                              //holding the file name into a string variable for later use
                              string strname = dlg.File.Name;
                              //creating a filestream and reading the contents of the selected file
                              using (Stream fileStream = dlg.File.OpenRead())
                              {
                                  //craeing a new IsolatedStorageFileStream for certaing new file in IsolatedStorage
                                  using (IsolatedStorageFileStream isoStream =
                                          new IsolatedStorageFileStream(strname, FileMode.Create, iso))
                                  {
                                      // Read and write the data block by block until finish 
                                      while (true)
                                      {
                                          //get the bytes to write in the file.
                                          byte[] buffer = new byte[fileStream.Length];
                                          // byte[] buffer = new byte[100001];
                                          int count = fileStream.Read(buffer, 0, buffer.Length);
                                          if (count > 0)
                                          {
                                              isoStream.Write(buffer, 0, count);
                                          }
                                          else
                                          {
                                              break;
                                          }
                                      }
                                  }
                                  txtStatus.Text = "Files Uploaded";
                              }
                          }
                      } 

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7. Delete File

In this section we will delete any file from the isolated storage area with the name as given by the user in te textbox. Moving towards the event Handler

 

private void btnDelete_Click(object sender, RoutedEventArgs e)
                      {
                          //getting the handler for the store
                          using (var MyAppStore = IsolatedStorageFile.GetUserStoreForApplication())
                          {
                              //Checking if file doesnot exist
                              if (!(MyAppStore.FileExists(txtFileName.Text)))
                              {
                                  //prompt the user that file does not exist
                                  MessageBox.Show("File does not exist ");
                              }
                              //if file does exist
                              else
                              {
                                  //delete it from the store
                                  MyAppStore.DeleteFile(txtFileName.Text);
                                  //prompt the user that the file is deleted
                                  MessageBox.Show("Deleted");
                              }
                              //clear the textbox containg the file name
                              txtFileName.Text = string.Empty;
                          }
                      } 

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The Code Is Attached you can Download the files and enjoy file handling


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Thanks and Regards
Meetu Choudhary
MVP.
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