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This is a property on a binding that controls the data flow from target to the source and used in two-way databinding scenarios. The default mode is when focus changes but there are number of other options available, which we will see in this article. Data trigger scenarios: Let’s talk about some of the data trigger scenarios.  By default, modified values in the binding controls only get pushed down when we do activity related to focus change like tab out, minimizing and maximizing window, etc. ·     In some scenarios we want to update values as quickly as possible, or let’s say with every key stoke.  So, to achieve such kind of scenarios Microsoft provided  UpdateSourceTrigger .  Properties available with  UpdateSourceTrigger : Default – This is the default value and it means a lost focus for most of the controls LostFocus – Value updation will be on hold until the focus moves out of control PropertyChanged – Value updation will happen whenever a target property

Here I am going to briefly introduce with the types of custom controls one can build in WPF. Someone can ask why we need custom controls, if we can do everything with Styles and Control Templates ??? Well, I would say still there are scenarios where one may need custom controls. One of them can be, while creating reusable control which is composed of many other controls, i.e: I want to create a control for data entry purpose, which will take Temporary address and Permanent Address. Here I don’t want to copy/paste XAML code repeatedly for these two addresses. So, it’s better to create a one User Control and reuse it. Another scenario can be, when we need a functionality which is not provided by existing WPF controls, here custom control can be the best solution. UserControl vs Control Now before proceeding further, it is important to have a look at the two most common classes of WPF namely UserControl and Control . UserControl should be chosen when you want to combine ex

Recently I received a request from one of the followers on ways to bind source objects. So, I thought it would be a nice topic for a post. Hence, it's here. For a binding to work, there should be a source object. The selection of source object is totally dependent on the way binding is used. If no binding source is provided, then bydefault DataContext of an element is used. The most common way is to set DataContext on parent element and let it flow to all its children. But apart from this, there are 3 other ways by which one can point to source object:  1) RelativeSource - Relative source is one of the property on a binding that can point to relative source markup extension which tells where the source can be found in hierarchy. In simple words, it is the relative path in the element hierarchy. 2) ElementName - Another way of specifying source is by using ElementName in which other element present in the current UI can be used as a source object. Here the source object

Nowadays MVVM is one of the most common architectural structure and hope most of us working on WPF, Silverlight, Windows Phone or Windows Store apps might have come across this. When talking about MVVM, the first thing which strikes in mind is INotifyPropertyChanged interface. The usual and most common practice of implementing INotifyPropertyChanged is: public class ViewModelBase : INotifyPropertyChanged     {         public event PropertyChangedEventHandler PropertyChanged;         protected void RaisePropertyChanged(string prop)         {             if (PropertyChanged != null)             {                 PropertyChanged(this, new PropertyChangedEventArgs(prop));             }         }     } What do you think about the above code? In first sight, it looks correct, but is it really perfect or thread safe? Well, here answer is NO. One very minor thing is missing in above code which can lead your application to crash in multi-threaded environment. If you will inspec

In continuation to my previous article titled ' Dynamically selecting DataTemplate for WPF ListView ', in this article, I am discussing about the alternative way to achieve the same goal. But here, to make the example simple, I am going to display only Employee names as shown below: Now this to achieve this, I am going to inherit MarkupExtension class provided by Microsoft. This class will give me the DataTemplate. If you will explore further, you will came to know that this MarkupExtension class has only one method named as ProvideValue, which will return me the appropriate template based on the supplied value.  Before inheriting MarkupExtension, I created a class named MyDataTemplateDictionary, which will inherit Dictionary<object, DataTemplate>. Please note, here key will be my DataTemplate name and value will be the DataTemplate. Below is the code depicting the same: Next comes is the class inheriting MarkupExtension. As there is nothing

Recently I get a chance to work on a project in which requirement was to select different different types of data templates based on the data. I faced bit difficulty, but afterwards I was manage to get it work. Let's have a look at the scenario first: Inside a WPF ListView, there are two GridViewColumns for storing Name and Age. Now requirement is to highlight the name of the person based on certain age criteria. If age is below 25, then name should be highlighted as red else it should be in green color, with desired background. I know there are ways to implement this using the concept of triggers, but I personally refrain from using triggers due to performance fall back. So, what else ??? The option left was dynamically selecting data templates. In this post I am going to write about the simplest approach and later on I'll do the same thing using Dictionary. Well, let's begin with our code. First of all, I created a class named Employee and added some data which w