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New Message on BDOTNET
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From: Nasha
Message 1 in Discussion
Hey Group,
To continue with our exploration on Isolated Storage Let us go ahead and create
a sample application.
1) Open a new Win App Place one listbox, one textbox and one button on the
form.
2) Our gaol is to serialize the contents of the listbox when the application
shut downs and when the application runs it should load the serialized data
back. IsolatedStorage works in a similar way as the file system . You can say
it is a special type of file system which is specific to your application.Only
your application knows where the files are stored.
3) Getting started we will create a .txt file for our application in
IsolationStorage which will hold all the serilized data. We first need to get
the reference of the IsolatedStorage Store for out application. We do that by
calling a static function of IsolatedStorageFile object called GetStore.
4) Add code in the click event of the button to add the text entered in the
textbox as an item in the listbox
listBox2.Items.Add(textBox1.Text);
textBox1.Text = "";
5) Since we have got reference to the store we can go ahead and create our
textfile to store our data.We need to serialize all the items in the listbox.
We will handle this in the Form Closing event.
6) Get the reference to the Application Store by calling GetStore method on
IsolatedStorageFile class
IsolatedStorageFile isf =
IsolatedStorageFile.GetStore(IsolatedStorageScope.Assembly |
IsolatedStorageScope.User,null,null);
If you check out all the other static methods of this object you will see that
there are specific methonds to get Isolated Stores for User and Application
Domain called as GetUserStoreFor Assembly and GetUserStoreForDomain. While
calling this function remember to put a combination of two or more options for
IsolatedStorageScope. This does not take a single value. Here we have given the
scope as Assembly and User.
7) Our second step will be to create a text file to hold our data. So we create
a file named "IsolatedStoreProj.txt" using the IsolatedStorageFileStream
object.
IsolatedStorageFileStream isfs = new
IsolatedStorageFileStream("IsolatedStoreProj.txt",System.IO.FileMode.OpenOrCreate,System.IO.FileAccess.ReadWrite,System.IO.
FileShare.ReadWrite,isf);
8) Now just loop through the items in the listbox and serialize all the data in
the text file. After wrting the data in the file stream close the file
stream.You complete code should look something like this :-
private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs
e)
{
IsolatedStorageFile isf =
IsolatedStorageFile.GetStore(IsolatedStorageScope.Assembly |
IsolatedStorageScope.User,null,null);
IsolatedStorageFileStream isfs = new IsolatedStorageFileStream
("IsolatedStoreProj.txt",System.IO.FileMode.OpenOrCreate,System.IO.FileAccess.ReadWrite,System.IO.
FileShare.ReadWrite,isf);
string [] sItems = new string[10];
listBox1.Items.CopyTo(sItems,0);
string oneString = null;
for(int i=0;i<sItems.GetLength(0);i++)
{
if(sItems[i] != null)
oneString += sItems[i].ToString() + ",";
else
break;
}
oneString = oneString.Substring(0,oneString.Length - 1);
System.Text.ASCIIEncoding asc = new System.Text.ASCIIEncoding();
byte [] byteArray = asc.GetBytes(oneString);
isfs.Write(byteArray,0,byteArray.GetLength(0));
isfs.Close();
isf.Close();
}
9) Compile and run this code. On exiting the application a text named
IsolatedStoreProj.txt should be created. This file will be created in at the
follwoing location
<drive>:\Documents and Settings\<user>\Local Settings\Application
Data\IsolatedStorage\<some folder>\<some
folder>\AssemFiles\IsolatedStoreProj.txt
10) Open the file and you will be able to view the contents we had serialized.
11) Now let us load this data when our application starts up. We will read this
file in the form_load event and populate our listbox.
private void Form1_Load(object sender, System.EventArgs e)
{
IsolatedStorageFile isf =
IsolatedStorageFile.GetStore(IsolatedStorageScope.Assembly |
IsolatedStorageScope.User,null,null);
IsolatedStorageFileStream isfs = new IsolatedStorageFileStream
("IsolatedStoreProj.txt",System.IO.FileMode.OpenOrCreate,System.IO.FileAccess.Read,System.IO.FileShare.Read,isf);
byte[] byteArray = new byte[10000];
isfs.Read(byteArray,0,(int)isfs.Length);
System.Text.ASCIIEncoding asc = new System.Text.ASCIIEncoding();
string twoString = asc.GetString(byteArray);
string[] oneArray = twoString.Split(new char[]{','},10);
for(int i=0;i<oneArray.GetLength(0);i++)
listBox2.Items.Add(oneArray[i]);
isfs.Close();
isf.Close();
}
12) In this way we can store our user setting , application related data in the
Isolated store.
13) This store that we have created in our sample application is a non-roaming
store. To create a roaming store give the scope as IsolatedStorageScope.Roaming
along with assembly and user as specified above.
14) WinNT and Operationg systems after it have a feature called as roaming user
profiles which allows the user to carry his perferences and presonal settings
across machines on the network.On the same lines .Net provides us with roaming
assembly stores so if the user has a roaming Windows profile his roaming
assembly store will also roam.
15) The assembly store is roaming only if it is mentioned explictly by
mentioning the IsolatedStorageScope if it is not then the scope is non-roaming
by default. Even if the user profile is roaming the isolated store can be
non-roaming.
16) You can create and list stores through code as well as use storeadm.exe for
the same ( as per Part -1).
-- Please post your queries and comments for my articles in the usergroup for
the benefit of all. I hope this step from my end is helpful to all of us.
Regards,
Namratha (Nasha)
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