Accessing WPF controls on a non UI Thread

March 14, 2010 Leave a comment

I am sure most of you would have run into this issue before. When you try to access a WPF control on a different thread other than your regular UI thread you get a runtime exception “The calling thread cannot access this object because a different thread owns it.”. To understand why this happens, it is important to know that WPF applications run on two different threads – one for rendering the controls and the other to manage the user interface. The rendering thread runs in the background and the thread which is visible for us to work on is the UI thread. And hence most of the objects are tied to the UI thread and this is known as thread affinity. Thread affinity is handled by the Dispatcher. Each user interface related work item is channeled through the Dispatcher class, that means every work item is queued by the UI thread in an object called Dispatcher. Dispatcher runs the work items on priority basis. Supporting work item prioritization allow WPF to work on a an item for more time and hence more time is consumed on the UI thread. UI thread will have at least one Dispatcher, and each Dispatcher can execute work items in exactly one thread. So it is important to release the work item from the thread as fast as possible so as to increase the UI responsiveness.  To keep the work item small,  I spawned newer threads and executed the discrete blocks of code on these threads. This is exactly where I ran into the exception stated above (when I tried to access the  WPF control).

So here is how I got the exception:

private void myButton_Click(object sender, RoutedEventArgs e)
{
    Thread t = new Thread(new ThreadStart(
        delegate
        {
            //accessing the TextBlock.Text on a different thread – **incorrect**
            myText.Text = "HI";
        }
        ));
    t.Start();
}

 

So how to get rid of this?

Now we know why a background running thread cannot access the UI thread. To get rid of this problem it is pretty simple – “Just ask the UI thread to do it for you”. Yes the background thread can request the UI thread to update the control properties on behalf of it. This is achieved by calling the Invoke or the BeginInvoke method of the DispatcherObject class. This will register the work items to the Dispatcher. Invoke is a synchronous call – that is, it doesn’t return until the UI thread actually finishes executing the delegate. BeginInvoke is asynchronous and returns immediately. So as stated above Dispatcher orders work items by priority and hence you can pass the priority using DispatcherPriority enumerator while registering the work item to Dispatcher. 
So here is the code below which solved my problem:

private void myButton_Click(object sender, RoutedEventArgs e)
{
    Thread t = new Thread(new ThreadStart(
        delegate
        {
            Dispatcher.Invoke(DispatcherPriority.Normal, new Action<TextBlock>(SetValue), myText);
        }
        ));
    t.Start();
}

private static void SetValue(TextBlock txt)
{
    txt.Text = "HI";
}

In the Dispatcher.Invoke() method used above takes three parameters – DispatcherPriority Enum, Delegate to execute the code and the parameter object. I used the Action<T> generic type to pass the control to the method to set its property.

It is suggested to use the setting of the control properties in the UI thread itself, and only move those code like say calculations to another thread. This will provide a better code maintenance.

However in the above example we do not improve the UI responsiveness, as the Invoke() method is called synchronously. Instead use BeginInvoke() method. My intention was to give an insight of the exception – why, and how to deal with it. If you need details on writing better responsive applications refer Shawn Wildermuth’s article

Wow another weekend in research -Cheers!

Categories: C#, WPF Tags: , , , ,

Success in entrepreneurship is for the one who is prepared

January 19, 2010 Leave a comment

Everyone say “Entrepreneurship isn’t easy and not meant for all”. As an experienced kid I do agree. But why isn’t it easy for all? When college drop outs like Bill Gates, Steve Jobs and Mark Zuckerberg can do it then why can’t others? I looked back to see what went wrong in my case. I am writing this down so that, I don’t forget these in my next venture. If this helps you do let me know.

Have A Great Idea, But Sellable –
Just because you have a great idea, it doesn’t mean that you have customers for it.It is important to have a market. Identify the need, make sure your solution is unique and deliver with quality.

Have A Vision -
Vision is the key. If you have an idea and a market you are sure shot to go. But will you sustain? Can you resist the change? Vision is not just a statement you need to add it to your about us page. It should be the one which you strictly follow at every stage. Have milestones and look back if you are aligned to the vision.Make sure every one in the company values the vision and follows it. Write down your vision on the paper and put it into a the board discussion. Remember how Microsoft is committed to its vision “Computer on every desk and in every home”. Today almost every one has a computer which is personal and running a Windows in it.

Choose Right Partners -
Your best friend is not always a right business partner for you. Because you care for your relationship you shouldn’t bring him/her into your business- That’s why they say “Mind Your Own Business”. Money plays a major role in business and but in relationships it is negative. So if you care for them then DO NOT. Your partner is one who stays by you during success as well as failure. Usually it happens the other way when you have your friend in business – He stays with you during success but blames you when you fail. Your partner should think like you, have passion like yours, should be committed like you and should have his/her own capability to make things right. Things fall into place faster when you have partners in different domains like marketing, technology, human resource etc. As they say the Lions, Tigers and other animals constitute a Jungle :) .

Plan Your Capital, Have A Business Plan -
$$$$Money$$$$ Where is the money to invest? What if i loose? I am a family man. The fear – setback. “Money is everything” Money is not everything but money is needed for everything. Its not right to believe that only a rich kid can do a business. Anyone with a smart business plan can do. A business plan is a written description of your business’s future. It should have key inputs like:

1. Executive summary
2. Business description
3. Market strategies
4. Competitive analysis
5. Design and development plan
6. Operations and management plan
7. Financial factors
*source: entrepreneur.com
If you have the fear of investing but you believe in your idea you still can do a great business. I agree that you cannot bring in huge capital into your business, instead approach a venture capitalist with your business plan. Convince him on the Return On Investment(ROI), if it interests him; he will help. VCs just eat up your stake because they are the risk takers. Don’t be greedy just sell your idea and give returns.

Hire Smart People -
Hire smart people on board and give them your best – the Google way. You should have managers who understand your business, maintain business secrets and take right decisions for you. Do not get involved in micromanagement it spoils everything. If you have hired a smart guy, you should leave the decision to him. Make them feel special and motivated at every stage. They are not just your employees, they are the people who are committed to you and the company. They are the reason for your success and you are the reason for the failure.

Have A Process -
You need not be a CMM level company to have a process. If you define a process now, you don’t have to repent later. Your process need not be complicated, but simple enough to take care of everyday activity. In your process make sure you keep milestones and measure your progress.

Change is Constant
Keep changing with times. No business can last long everything has a saturation. Identify the change early and get ready for the future. Once you have the idea which is already in the market, a great vision, hired smart people, and put a process in place then whats your job? – Smell the future, plan, and get ready!

These are just few of the points I remembered when I looked back at my failure. May be this is just right to my situation. Let me know if you guys have some other key points that I should keep in mind.

Some resources:
5 Myths That Can Kill a Start-Up
Entrepreneur

Cheers!

Categories: Entrepreneurship

Animated Gif in WPF using Windows Forms Control

January 11, 2010 3 comments

Loading an animated gif into WPF has been a challenge since the version 1 release. WPF does not support loading an animated gifs directly into an declarative <Image> or by code, and hence developers have come out with various workarounds. Some use a raw technique – writing few lines of code which extracts the frames of the GIF and animate them.  One other way to do is using the <MediaElement> FrameworkElement which is in the namespace System.Windows.Controls. <MediaElement> wraps the MediaPlayer class for declarative use and hence it supports both audio and video files. Using MediaElement you can load the animated gif the following way:

<MediaElement Source="file://D:\anim.gif"/>

Remember it is important to use “file://” and an absolute path for loading the gif. So you cannot embed the image to a resource file and now you know one of the limitations of it. Every approach does have advantages and limitations of its own, its important to use the right approach based on the project needs.

Another possible way is by making the working Jack do the trick – Yeah I meant lets go back to Win Forms picture box to do the magic. We know PictureBox seamlessly loaded the animated gifs in Win Form days. Wait a minute did I say lets change the project from WPF to Win Forms? No I didn’t. What I said is lets integrate the PictureBox alone to the WPF project. To use the right word, I should say that we need to host the Windows Forms Control in WPF. To host a Windows Forms Control you need to make use of the class WindowsFormsHost which appears in the System.Windows.Forms.Integration namespace in assembly WindowsFormsIntegration.dll.

Lets get to the code. The first step to do is add a reference to System.Windows.Forms.dll and WindowsFormsIntegration.dll to your WPF based project.

References

Add the following namespaces to your XAML Code.

<Window x:Class="WpfApplication2.Window1"
    xmlns:wfi="clr-namespace:System.Windows.Forms.Integration;assembly=WindowsFormsIntegration"
    xmlns:winForms="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"

Now you can host the PictureBox inside the WindowsFormsHost and set its Name.

    <Grid>
        <wfi:WindowsFormsHost>
            <winForms:PictureBox x:Name="pictureBoxLoading">
            </winForms:PictureBox>
        </wfi:WindowsFormsHost>
    </Grid>

In your code behind(Window1.xaml.cs), add this code to the Window_Loaded Event:

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            this.pictureBoxLoading.Image = System.Drawing.Image.FromFile("anim.gif"); ;
        }

Key points before execution:

  1. Make sure you provide the right path to load the image
  2. You can also load it from a resource file.

Since Windows Forms has several interesting built in controls that WPF lacks, using this technique you can make your favorite Windows Forms control work in WPF.

Cheers!

Categories: WPF Tags: , , , ,

Error: Not enough storage is available to process this command

October 31, 2009 3 comments

Today afternoon I was on a mission to complete a long pending personal project and as part of it I was developing a windows service which extended the support of starting and stopping the service from a console window. After the completion it was time for me to start testing that out and then this weird thing happened. Whenever the system encountered a Console.ReadLine(), it gave me a strange error: “Not enough storage is available to process this command.”  But executing a Console.WriteLine() was not an issue. After playing around with it for a while I figured out the project I had selected was Windows Service and hence it’s output type was Windows Application. Changing the project type to a Console application did the trick. Hopefully this helps someone.

Cheers!

Categories: C#, ConsoleApp Tags:

Best blog award and me?

October 25, 2009 2 comments

This is really amazing. Blogging was one of the activities I thought I was never good at. My last experience at the tech-ed forced me to write one, and this is truly surprising – Won the best blog award for writing down my experiences at the event. I received a Windows Vista Ultimate licensed copy from Vic at Xperience 2009/ Microsoft Community Tech Days event. This is my first blog entry and what a great way to start – It inspires! Thanks to BDotnet and BITPro panel members. 

Thank you VJ(MSIGeek) for scheduling the prize giving session little earlier than it was planned. It will not be good on my part if I do not mention a special thanks to VJ for having this session clicked for me and for Vic’s patience.

BestBlogBdotnet

WindowsVistaUltimate

Cheers!

Categories: tech-ed 2009, Xperience2009 Tags: ,

Custom Configuration Section in C#

September 17, 2009 9 comments

A very familiar way of implementing the frequently changing value in an application is by storing them in a configuration file’s <appSettings> section. When the project is big, storing too many values in application settings is not a suggested approach, as this can lead to confusions and many other integration problems. Many at times we have seen when the code is moved from a development environment to a production environment there is a mismatch in the the configuration or we loose out on some important values. These issues can be eliminated by simply using a custom configuration section. A project constitutes of many modules and each module will have configuration values specific to them. So it will be a good idea to group them to a single section, and every  module’s configuration values will reside in their respective section. This way by just looking at the configuration one can figure out which value relates to what module. It is also suggested to have a common section so that these values can be accessed by all the modules and will reduce duplication of values.

Going forward you will learn about creating custom configuration section, the corresponding value holder class, and properties to access them through out the application. I will make the demo simple to a console application, so that it is easy to understand.

Start a new Console application and add an application configuration file to it. Also reference System.Configuration.dll.

What’s in the Configuration?

  1. <?xml version=“1.0“ encoding=“utf-8“ ?>
  2. <configuration>
  3.     <configSections>
  4.         <section name=“MyConfiguration“ type=“ConfigurationC.MyConfiguration, ConfigurationC“/>
  5.     </configSections>
  6.     <!– Configuration settings for MyConfiguration Starts –>
  7.     <MyConfiguration
  8.             To=“support@nnish.com“
  9.             From=“sales@nnish.com“>
  10.         <Messages>
  11.             <Message Name=“Email“ Value=“email“/>
  12.             <Message Name=“Sms“ Value=“sms“/>
  13.             <Message Name=“Tweet“ Value=“tweet“ />
  14.         </Messages>
  15.     </MyConfiguration>
  16.     <!– Configuration settings for MyConfiguration Ends –>
  17. </configuration>

Lets break this into bits and pieces. Notice the <configSections> element –this is where you register your custom configuration. To add a custom configuration – add an element <section name=”” type=””/>.

  • name – represents the name of the custom configuration
  • type – used as <namespace.Type>, <AssemblyName> (Type is the corresponding class which inherits ConfigurationSection)

And the <MyConfiguration>element is nothing but the custom configuration section which contains custom values stored.  I will explain multiple ways of storing in the config files and accessing them from the application. In the config, I store some values as the attribute of the main element, the main element has the sub element <Messages> and that in turn has the collection of <Messages> having attributes “Name” and “Value”. This can be easily related to <add> element in the <appSettings>.

What’s in the Code?

Now let us go ahead and build the classes for accessing these values in the application.

Remember these:

  • There should be a class in the application representing each element (including the sub elements) in the configuration file.
  • Class holding the custom Configuration Section should inherit from CustomSection
    • public class MyConfiguration : ConfigurationSection
  • The attributes/elements can be represented as a property which is of type ConfigurationProperty in the parent class.
  • Class representing an element collection should inherit from ConfigurationElementCollection
    • public class MessageCollection : ConfigurationElementCollection
  • Class representing an element should inherit from ConfigurationElement
    • public class MessageElement : ConfigurationElement

Since <Message> is the last child element, write the corresponding class for it first, and then <Messages> which is its parent and it holds the collection of <Messages> and finally the class for <MyConfiguration> which has attributes represented as properties in itself.

Element: <Message> – Class: MessageElement

  1. using System.Configuration;
  3. namespace ConfigurationC
  4. {
  5.     /// <summary>
  6.     /// Class holds the <Message> element
  7.     /// </summary>
  8.     public class MessageElement : ConfigurationElement
  9.     {
  10.         // Holds the Name attribute of the Message
  11.         private static readonly ConfigurationProperty messageName =
  12.             new ConfigurationProperty(“Name”, typeof(string), string.Empty, ConfigurationPropertyOptions.IsRequired);
  14.         // Holds the Value attribute value of Message.
  15.         private static readonly ConfigurationProperty messageValue =
  16.             new ConfigurationProperty(“Value”, typeof(string), string.Empty, ConfigurationPropertyOptions.IsRequired);
  18.         public MessageElement()
  19.         {
  20.             base.Properties.Add(messageName);
  21.             base.Properties.Add(messageValue);
  22.         }
  24.         /// <summary>
  25.         /// Name
  26.         /// </summary>
  27.         [ConfigurationProperty("Name", IsRequired = true)]
  28.         public string Name
  29.         {
  30.             get { return (string)this[messageName]; }
  31.         }
  33.         /// <summary>
  34.         /// Value
  35.         /// </summary>
  36.         [ConfigurationProperty("Value", IsRequired = true)]
  37.         public string Value
  38.         {
  39.             get { return (string)this[messageValue]; }
  40.         }
  41.     }
  42. }

Explanation:

  • <Message> element has attributes “name” and “value” which are represented as ConfigurationProperty and its initialization takes the following parameters
    • name: The name of the configuration entity.  
    • type: The type of the configuration entity.
    • defaultValue: The default value of the configuration entity.
    • options:  One of the System.Configuration.ConfigurationPropertyOptions enumeration values
  • In the constructor add these properties to the base class Property Collection
  • Expose them as public property

Element: <Messages> – Class: MessageCollection

  1. using System.Configuration;
  3. namespace ConfigurationC
  4. {
  5.     [ConfigurationCollection(typeof(MessageElement), AddItemName = "Message",
  6.          CollectionType = ConfigurationElementCollectionType.BasicMap)]
  7.     public class MessageCollection : ConfigurationElementCollection
  8.     {
  9.         protected override ConfigurationElement CreateNewElement()
  10.         {
  11.             return new MessageElement();
  12.         }
  14.         protected override object GetElementKey(ConfigurationElement element)
  15.         {
  16.             return ((MessageElement)element).Name;
  17.         }
  18.      
  19.         new public MessageElement this[string name]
  20.         {
  21.             get { return (MessageElement)BaseGet(name); }
  22.         }
  23.     }
  24. }

Explanation:

  • MessageCollection class is inherited from the abstract class ConfigurationElementCollection and two of its abstract methods CreateElement() and GetElementKey() needs to be overridden
  • CreateElement() creates the new instance of the MessageElement
  • GetElementKey() Gets the element key for a Message element (we define Name attribute as the key, so that the value can be retrieved using the name)
  • new public MessageElement this[string name] – add this to retrieve the value with the key name. For e.g: ConfigurationManager.AppSettings[“test”];

 

Element: <MyConfiguration> – Class: MyConfiguration (Putting them all together[ConfigurationSection ])

  1. using System.Configuration;
  3. namespace ConfigurationC
  4. {
  5.     public class MyConfiguration : ConfigurationSection
  6.     {
  7.         private static readonly ConfigurationProperty toAttribute =
  8.              new ConfigurationProperty(“To”, typeof(string), string.Empty, ConfigurationPropertyOptions.IsRequired);
  9.         
  10.         private static readonly ConfigurationProperty fromAttribute =
  11.              new ConfigurationProperty(“From”, typeof(string), string.Empty, ConfigurationPropertyOptions.IsRequired);
  13.         private static readonly ConfigurationProperty messagesElement =
  14.              new ConfigurationProperty(“Messages”, typeof(MessageCollection), null, ConfigurationPropertyOptions.IsRequired);
  16.         public MyConfiguration()
  17.         {
  18.             base.Properties.Add(toAttribute);
  19.             base.Properties.Add(fromAttribute);
  20.             base.Properties.Add(messagesElement);
  21.         }
  23.         /// <summary>
  24.         /// To
  25.         /// </summary>
  26.         [ConfigurationProperty("To", IsRequired = true)]
  27.         public string To
  28.         {
  29.             get { return (string)this[toAttribute]; }
  30.         }
  31.         
  32.         /// <summary>
  33.         /// From
  34.         /// </summary>
  35.         [ConfigurationProperty("From", IsRequired = true)]
  36.         public string From
  37.         {
  38.             get { return (string)this[fromAttribute]; }
  39.         }
  41.         /// <summary>
  42.         /// Messages Collection
  43.         /// </summary>
  44.         [ConfigurationProperty("Messages", IsRequired = true)]
  45.         public MessageCollection Messages
  46.         {
  47.             get { return (MessageCollection)this[messagesElement]; }
  48.         }
  49.     }
  50. }

Explanation:

  • Add all the Attributes and Elements as the ConfigurationProperty of corresponding type.

And the Program.cs

  1. using System;
  2. using System.Configuration;
  4. namespace ConfigurationC
  5. {
  6.    public class Program
  7.     {
  8.         public static MyConfiguration MyConfig;
  10.         static void Main(string[] args)
  11.         {
  12.             MyConfig = GetConfiguration();
  14.             Console.WriteLine(“This program comes with no warranty!”);
  15.             Console.WriteLine(“Values found in the configuration”);
  16.             Console.WriteLine(“To: “ + MyConfig.To);
  17.             Console.WriteLine(“From: “ + MyConfig.From);
  18.             Console.WriteLine(“Message Email: “ + MyConfig.Messages["Email"].Value);
  19.             Console.WriteLine(“Message Sme: “ + MyConfig.Messages["Sms"].Value);
  20.             Console.WriteLine(“Message Tweet: “ + MyConfig.Messages["Tweet"].Value);
  21.             Console.ReadLine();
  22.         }
  24.         private static MyConfiguration GetConfiguration()
  25.         {
  26.             return (MyConfiguration)ConfigurationManager.GetSection(“MyConfiguration”);
  27.         }
  28.     }
  29. }

Above code snippet is self explanatory.

I hope I was able to walk you through a step by step process of a developing hello world Custom Configuration section.

Download the code!

Cheers!

Categories: C#, Custom Configuration Tags: , ,

Internet Explorer 8 ViewSouce Viewer

July 30, 2009 Leave a comment

When you hit the “View Source” command in IE, it opens in a refreshing viewer. I mentioned viewer because you are not allowed to edit :) .  Previous version used the notepad as an editor. If you still want to use the notepad as the default editor then press F12 to open developer tools Click File-> Customize Internet Explorer View Source –> select – Notepad. And one more thing to be mentioned – Developer tools Fantastic.

IE8ViewSource

Here is the developer tool screenshot:

image

Check out the Menu Items to know what you can do with this handy tool bundled with IE8.

 

Cheers!

Categories: Internet Explorer 8 Tags: ,
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