Tips ‘n’ Tricks


8
Jan 12

DoUNo: ApplicationBar in WindowsPhone is not bindable

ApplicationBar is not a FrameworkElment and is not bindable. Which implies that if you are so much used to MVVM and wants to bind things to ApplicationBar, its not easy; you need to create your own ApplicationBar.

This sounds pretty lame and I really don’t know why Microsoft is not interested in creating an ApplicationBar that is bindable.


29
Dec 11

DoUNo: You can tombstone an app using Windows Phone Emulator

Property page of a WP project

Property page of a WP project

You cannot predict when an app would be tombstoned in Windows Phone. But still you can simulate it by enabling a settings in the Property page of the Windows Phone project.

  1. Browse to the Property page of the Windows Phone project.
  2. Select the Debug tab.
  3. Select the Tombstone upon deactivation while debugging.
  4. Build and Run the project.
  5. After the app launches, click on the Windows key to deactivate the app, there by tombstoning it.

8
Jan 11

From .net to iOS

Its been a week since I started off with application development using iOS. So far the experiences has been awesome. So if you want to write programs for iPhone/iPod/iPad, all you gotta do is,

  1. Get a Mac. You cannot develop apps from your pc. I tried using virtual machine, but it is NOT POSSIBLE AT ALL. Forget about your pc. Go get your mac !!
  2. Once you have your mac, navigate to http://developer.apple.com. You have so many resources out there which should get you on board immediately

Tips for beginners,

  • Development Center – is really neat and way ahead than MSDN
  • Programming Paradigm – is MVC and should be familiar if you were programming for quite a while
  • IDE – XCode and InterfaceBuilder are the IDEs with which you write programs for iOS. Thou’ they are not as good as Visual Studio, they are pretty good for beginners
  • Programming Language – ObjectiveC – so far is the biggest challenge for me. If you are new to this, you will find it to be really weird
  • Unmanaged Code – if you are a .net programmer with no experience writing C/C++ programs, you should be extra careful in here
  • Tutorials and Samples – development center has got everything for you. Do not worry about this

Overall, the experience is good and exciting so far.


20
Jul 10

DoUNo: Whadds up with the Background property of a control

This is weird !! Try to customize the control template of a button,

  1. Place a grid as the base panel (don’t add any Background property to it)
  2. Add an ellipse and a content presenter to this
  3. Add a Click event handler to the button
  4. Run it and try to click on the white space, the event will not be raised !!!

Go back to the template,

  1. Add a Background property to the grid and set the value to Blue (can be any color other than transparent)
  2. Run it and try to click on the Blue color, the event will be raised !!!

Go back to the template,

  1. Set the value of the Background Property to Transparent
  2. Run it and try to click on the white space, the event will still be raised !!! (WHY ?!?)

Looks weird to me thou’


13
Jan 10

Transparent background with opaque controls on top of it in wpf

Ever felt like having a transparent window background and still opaque controls inside the window? It can be easily done in wpf.

  1. Set the window’s AllowsTransparency to True
  2. Set the window’s Background to Transparent
  3. Add a Rectangle to the parent panel of the window
  4. Set the opacity of the rectangle to some value < 1 (0.7, …)
  5. Add your controls to the parent panel
  6. You are one step away form seeing a transparent background with opaque controls on top of it. Go ahead, run the application now

Sample window,

<Window x:Class=”BackgroundWindow.Transparent.Samples.WPF.Window1″
xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation”
xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml”
Title=”Window1″ Height=”300″ Width=”300″ AllowsTransparency=”True” Background=”Transparent” WindowStyle=”None”>
<Grid>
<Rectangle Fill=”Gray” Opacity=”0.7″ />
<Button Width=”100″ Height=”100″>Click this on</Button>
</Grid>
</Window>


13
Jan 10

DoUNo: MDI in WPF

WPF, out of the box doesn’t have provision for MDI windows. The reason is quite simple, MDI windows are outdated and most of the applications have been using tabbed documents, proving they are really easy to use. Although the framework is flexible enough for you to make such a feature, its better to move to tab based interface.


6
Dec 09

Mashing Twitter and FSO

I really love Twitter and it didn’t make any sense to me to shell out a rupee for every tweet sent through my Airtel Mobile. Moreover, I am on one of those monthly booster packs which allows you to send 22000 text messages for free. I simply had to exploit this by setting up my own little ‘OC’ twitter forwarder written in python. (I know of smstweet.in service but I am still charged 1.50 for every tweet I send)

Its insanely simple to write such a ‘forwarder’ in python using the services provided by the FSO (freesmartphone.org) Framework,

  1. Send messages to your old/unused number whose SIM is in the Freerunner (or any other device supported by the FSO framework)
  2. Handle the incoming messages and use python-twitter API (or) raw urllib2 to post updates. Of course, the device should be connected to the internet, you can tether this device to an old unused computer. Simply put, the Freerunner should be able to access the internet.

I know this is dumb given cheap GPRS and all, but what the heck; Sundays _are_ reserved for dumb things and I wanted to show off how easy it is to develop and conjure up simple but powerful scripts using open hackable hardware like the Freerunner. So take off your pedantic hats ;)

Here is the actual python code,

#!/usr/bin/env python
# Written By Sudharshan S, http://sudharsh.wordpress.com
 
import dbus
import time
import logging
import twitter
 
import gobject
from gobject import MainLoop
 
from dbus.mainloop.glib import DBusGMainLoop
DBusGMainLoop (set_as_default = True)
 
# Use OAUTH?
USERNAME = "username"
PASSWORD = "password"
 
log = logging.getLogger("TweetForwarder")
 
class TweetForwarder:
 
   """Process Incoming messages and update twitter status
      if the message startswith 'tweet'
   """
 
   def __init__(self, username, password):
       log.warning("Starting up....")
       self.twitter_api = twitter.Api(username=username, password=password)
 
       # Get proxies and add signal handlers
       bus = dbus.SystemBus()
       _usage = bus.get_object("org.freesmartphone.ousaged",
                               "/org/freesmartphone/Usage")
       _proxy = bus.get_object("org.freesmartphone.ogsmd", \
                               "/org/freesmartphone/GSM/Device")
       self.usage_iface = dbus.Interface(_usage, "org.freesmartphone.Usage")
       self.usage_iface.RequestResource('GSM')
       self.sms_iface = dbus.Interface (_proxy, "org.freesmartphone.GSM.SMS")
       self.sms_iface.connect_to_signal ("IncomingMessage", self.onIncomingMessage)
 
   def onIncomingMessage(self, sender, message, kwargs):
       log.warning("Received SMS from %s:%s" % (sender, message))
       # We don't ALL messages to this number to be tweeted
       if message.strip().startswith("tweet "):
           log.warning("Trying to update status : %s" % message[6:].strip())
           self.twitter_api.PostUpdate(message[6:])
           log.warning("Updated Status")
 
   def run(self):
       loop = MainLoop()
       loop.run()
 
if __name__ == "__main__":
    logging.basicConfig()
    server = TweetForwarder(USERNAME, PASSWORD)
    server.run()
--

Make sure you have python-netclient and python-json installed on your Freerunner. These can be installed using the ‘opkg install’ command.

The script and the accompanying dependency can be downloaded from here. Just change the USERNAME and PASSWORD accordingly after scp’ing the tarball to your device.

Some useful links,

[1]: The FSO API reference

[2]: DBus Tutorial


3
Dec 09

DoUNo: Popup animation in wpf

Every time I try adding a default animation (Slide, Fade, …) to a pop up in WPF, I find it not to be working. Today, I went thru’ MSDN (breaking my laziness :P ) and found that the popup animation shall work only if the AllowsTransparency of the popup is set to true. Really weird !!


6
Nov 09

DoUNo: Setting expectations on nullable type, NMock2

Ever had a problem of setting an expectation for nullable objects?

If you wanna return false when .HasValue of a nullable object is called, then you cannot do it with the normal expect statement. Rather, try not returning any values, because NMock2 returns default value of HasValue (False) if nothing is set as return values in expect statements.

Here is a sample,

public interface IProduct  //Interface that has a nullable member
{
  int? ProductNo  //Member that I wanna test and I wish to test the scenario in which this will be null
  {
    get;
  }
}
IProduct aProduct= myMockery.NewMock&lt;IProduct&gt;();
//Stub.On(aProduct).GetProperty("ProductNo").Will(Return.Value(default(int?));  //this statement produces a runtime exception, so we have to use the following instead
Stub.On(aProduct).GetProperty("ProductNo");  //no return value is set, nmock2 returns false when .HasValue is queries

Hope this helped you.

Sudarsan Srinivasan
- on behalf of my friends (they found this hack :P )


31
Aug 09

Accessing Command Prompt from C#

Recently, I wanted to write a program in c# that should start the command prompt in the background (it should not show the cmd window), give inputs from my C# program and get the results redirected back to my C# application. I was googling around a bit and then came up with a solution.

Its damn simple. Usually to start any process from C# applications, we use the Process object. The process object has two properties called StandardInput and StandardOutput. These properties will allow the C# application to get the input stream of the process that needs to be started. So to mock inputs and outputs, we need to do the following,

Process aProcess = new Process();
ProcessStartInfo aStartInfo = new ProcessStartInfo();
aStartInfo.FileName = Environment.GetFolderPath(Environment.SpecialFolder.System) + "\\cmd.exe";
aProcess.StartInfo = aStartInfo;
aProcess.StandardInput.WriteLine("dir");  //will open a cmd process and feed the command "dir" to it

By this way you could give inputs to a process that you start from C#. What if you wanna see output of the cmd prompt in your own prompt ?? For this we use the StandardOutput property. But there is yet another simple way to get the output from the command prompt. This is done by subscribing for the event, OutputDataReceived.

aProcess.OutputDataReceived += new DataReceivedEventHandler(Process_OutputDataReceived);
private void Process_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
  textBox1.AppendText(e.Data);
  textBox1.AppendText(Environment.NewLine);
}

Note: These ways are possible only if,

aProcess.RedirectStandardOutput = true;
aProcess.UseShellExecute = false;
aProcess.BeginOutputReadLine();

are set to the mentioned values. BeginOutputReadLine method will start async read operations from the C# application stream instead of the standard input devices. So next time you wanna clone a command prompt, start the cmd process and give your own look and feel to it.