Archive for the ‘Controls’ Category
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 
) and found that the popup animation shall work only if the AllowsTransparency of the popup is set to true. Really weird !!
In my previous post I had written about StackPanel. One big disadvantage with the StackPanel was with the wrapping part. It cannot wrap controls / contents when it overflows. Thats why we have the WrapPanel. This is StackPanel + Wrap enabled. The following example may help you understand this better.
Consider that you have a stack panel with 7 buttons arranged in a horizontal fashion and if your window’s width is smaller than the sum of seven button’s width, then this how it looks
<Window x:Class="LayoutsTest.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">
<StackPanel Orientation="Horizontal">
<Button Content="Button1" VerticalAlignment="Center" />
<Button Content="Button2" VerticalAlignment="Center" />
<Button Content="Button3" VerticalAlignment="Center" />
<Button Content="Button4" VerticalAlignment="Center" />
<Button Content="Button5" VerticalAlignment="Center" />
<Button Content="Button6" VerticalAlignment="Center" />
<Button Content="Button7" VerticalAlignment="Center" />
</StackPanel>
</Window>
A close substitute for this problem will be a WrapPanel.
<Window x:Class="LayoutsTest.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">
<WrapPanel Orientation="Horizontal">
<Button Content="Button1" VerticalAlignment="Center" />
<Button Content="Button2" VerticalAlignment="Center" />
<Button Content="Button3" VerticalAlignment="Center" />
<Button Content="Button4" VerticalAlignment="Center" />
<Button Content="Button5" VerticalAlignment="Center" />
<Button Content="Button6" VerticalAlignment="Center" />
<Button Content="Button7" VerticalAlignment="Center" />
</WrapPanel>
</Window>
Although this solves the Wrap problem of the stack panel, still we cannot place two controls paralle to each other using this panel.
As the name says you can dock your controls in to either Top, Left, Right or Bottom of the panel. Placing a control to a location can be done using the Dock property with the values Left, Top, Right and Bottom.
ln1: <DockPanel>
ln2: <Button DockPanel.Dock="Top" Content="Button1" />
ln3: <Button DockPanel.Dock="Bottom" Content="Button2" />
ln4: <Button DockPanel.Dock="Left" Content="Button3" />
ln5: <Button DockPanel.Dock="Right" Content="Button4" />
ln6: <Button Content="Button5" />
ln7: </DockPanel>
This will dock the button1 to the top of the container, button2 to the bottom and so on.
The order in which we dock the controls matters in here. If we move ln4 to ln3 and ln3 to ln4, the layout will look different.
If you dock a control to a location, the control will remain docked to that location irrespective to the size of the container. Take a look at the schreenshot shown below (with the container maximised).
Although this allows us to fix some controls to any edge of the container, we cannot position controls explicitly using this panel.
Like .Net 2.0, WPF provides a set of layouts that allows the users to easily place the controls in to it. Lets look in to it, one by one comparing with the net 2.0 version of it.
StackLayout
This was called as FlowLayout in .net 2. Controls that are added in to this layout will be automatically aligned either in a vertical or in a horizontal fashion. This alignment depends on the value of Orientaion property. The value can either be Vertical or Horizontal.
Vertical Orientation
<StackPanel Orientation="Vertical">
<Button Content="Button1" />
<Button Content="Button2" />
</StackPanel>
Horizontal Orientation
<StackPanel Orientation="Horizontal">
<Button Content="Button1" />
<Button Content="Button2" />
</StackPanel>
If you notice the screenshots, you will find that the width of the button is automatically controlled by the WPF framework. Thats why the buttons are stretched. But if you wanna control the width, you can play with the HorizontalAlignment property of the control. The default alignment is Stretched. Specifying a width for the control along with the HorizontalAlignment property allows you to have total control on the size and location of the control.
<StackPanel Orientation="Vertical">
<Button Content="Button1" />
<Button Content="Button2" HorizontalAlignment="Left" />
<Button Content="Button3" HorizontalAlignment="Right" />
<Button Content="Button4" HorizontalAlignment="Center" />
<Button Content="Button5" HorizontalAlignment="Stretch" />
</StackPanel>
We can see this layout in action in loads of places. For example, the search tool that comes with windows has employed this layout.
Although this layout lets the us relax on alignments, we cannot place two controls parallel to each other (this layout is not intented to do so. we have another layout for this, GridLayout). Also this layout cannot wrap controls when the controls overflow (again this layout is not intented to do so. we have another layout for this, WrapPanel).
Browsing about UI guideline, I got a superb link. Its a must read for UI designers. Also take up the quiz when you are done with the link.
Recently, I was trying to write UnitTest for a panel. The panel had a ComboBox and the target method (method that needs to be tested) was populating the ComboBox with some DataSource, which is a collection of string. In my unit test driver (written in NUnit with NMock), I tried to check the item’s collection. It was always returning me null despite me adding some items to it. Even the SelectedItem and SelectedIndex were all returning me null. When I had a look in to the WinForms dll using reflector, I came to know about itemscollection .
It seems that this member will not be populated unless the ComboBox is painted in a layout.
So next time, when you are writing a unit test for controls, make sure that you create testcases that are testable (unlike me). Thanks to my colleague who pointed out a SO link that clearly talks about this.
I have a ComboBox whose items are set using the DataSource property. The DataSource is a collection of a custom object (that has a string property ‘Value’ and int property ‘Id’). In the initialise controls, I set the DisplayMember as Value and ValueMember as Id. Now I tried to clear the DataSource by calling,
myComboBox.DataSource = null;
When I did that, my ComboBox’s DisplayMember is reset to “” automatically. This was not I expected, but this is how it behaves as a .Net control. Thought it would be helful sharing it.
More @ http://stackoverflow.com/questions/641809/displaymember-getting-reset-on-datasourcenull
Today, I was trying to customise ListViewControl by playing with the item drawn event, thats when I came across this peculiar stuff.
In ListView, if you have subscribed for the ItemSelectionChangedEvent,the event will not be raised, if you select the same item more than once provided the ListView.MultiSelect = false; Shhh. Quite difficult to understand, isn’t it ??
Ok. An example, Lets consider that we have a list view control with two items, foo and bar. Also consider that we have subscribed for the ItemSelectionChangedEvent and the ListView’s MultiSelect is true. Now if you run the application keeping a break point in the ItemSelectionChangedEventHandler and if you select the item foo again and again the control will break. On the other hand, if your ListView’s MultiSelect is false, the control won’t hit the break point. Which means that the event will not be raised.
When you create a ListViewItem in C#, it automatically creates a ListViewSubItem for it and the ListViewItem.SubItem[0] is the ListViewItem.
i.e, the default value of ListViewItem is the value of ListViewItem at SubItems[0]
You can find more about ListViewItems in http://codelog.blogial.com/2008/07/18/using-listview-control/
Refer to http://stackoverflow.com/questions/502782/automatic-creation-of-listviewsubitems to know my experiences with the ListViewControl.
ListViewControl
The folder list pane that you see in a Windows Explorer is called TreeViewControl. In C#, its really easy to use these controls. There are loads of facilities provided by this control. Some of them are really great. In this post, I will try to explain some of the basics of this control.
Adding a TreeViewControl
To add a TreeView control, just double click on the TreeView control from the Tools window or add the snippet,
TreeView myTreeView = new TreeView();
this.Controls.Add(myTreeView); //adding the control to the presentation form
Adding a Node
Nodes are the items that you can find in a tree view control. This is the tricky part. You can have a node, that has another node, that has one more node, and so on. Just like the files and folders inside another folder. To add a node, the control has got, Nodes.Add() method. This is a overloaded method and it has loads of overloaded parameters. For example, you can have a string as a parameter to this method to add a node.
myTreeView.Nodes.Add("foo"); //will add a new node with the text foo in it
