Category Archives: Programming

The WPF ComboBox

The other major listing control to cover is the ComboBox. It turns out that they are almost identical to ListBoxes. This simple code will add a combo box to your container (I’m using a StackPanel) and put two items into it.

      <ComboBox>

        <ComboBoxItem>Item 1</ComboBoxItem>

        <ComboBoxItem>Item 2</ComboBoxItem>

      </ComboBox>

Running will produce the predictable window with a drop down combo box and two items. If you want the user to be able to edit or enter his own text, you will need to set the IsEditable property to true and IsReadOnly to false in the <ComboBox> header.

Also like the ListBox, the ComboBox can contain complex items.

      <ComboBox>

        <ComboBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Anna</TextBlock>

            <Image Source=D:\Presentations\100Anna.jpg Height=100 />

          </StackPanel>

        </ComboBoxItem>

        <ComboBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Raven</TextBlock>

            <Image Source=D:\Presentations\100Rave.jpg Height=100 />

          </StackPanel>

        </ComboBoxItem>

        <ComboBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Ammie</TextBlock>

            <Image Source=D:\Presentations\100Ammie.jpg Height=100 />

          </StackPanel>

        </ComboBoxItem>

        <ComboBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Kids</TextBlock>

            <Image Source=D:\Presentations\100Kids.jpg Height=100 />

          </StackPanel>

        </ComboBoxItem>

 

      </ComboBox>

wpf040

Note from the image above, if the contents of the drop down are too big it wil drop below the bottom of your current Window. Additionally, if you use automatic sizing the combo box will adjust itself rather oddly depending on the contents. For that reason, you may wish to set a default width rather than letting the combo box do it for you.

So how do we get data back out of the ComboBox? Well, if all we have is text, we can do just like we did with the ListBox, convert the selected item to a combo box item and get it’s Content.ToString property. But what if it’s like the above example, a mixture of text and images? Well we have to dig just a little, but it’s not that difficult if you understand the tree WPF creates.

  <StackPanel>

    <ComboBox Name=myComboBox  >

      Item Data Omitted for Brevity

    </ComboBox>

    <Button Name=myButton Content=OK Click=myButton_Click />

  </StackPanel>

Note I made two changes. First I added a name to the ComboBox, that way I can address it in code. Next I added a simple button control, we’ll use it to show what is currently selected. Just for the fun of it, I used the Content tag instead of placing it between the <Button></Button> tags, you may run across that form of syntax at some point and should be aware of it.

Now we need to add a little code to the myButton_Click event.

    public void myButton_Click(object sender, RoutedEventArgs e)

    {

      ComboBoxItem cbi = myComboBox.SelectedItem as ComboBoxItem;

      if (cbi != null)

      {

        StackPanel sp = cbi.Content as StackPanel;

        TextBlock block = sp.Children[0] as TextBlock;

        MessageBox.Show(“You picked “ + block.Text);

      }

      else

      {

        MessageBox.Show(“You haven’t picked anything yet”);

      }

    }

First, I got the current ComboBox item, and stored it in the cbi variable. I then check to see if it’s null, which it will be if the user hasn’t selected anything. If it is, we can show them the traditional “hey dummy” message, as I did in the else clause.

If you recall, the contents of the ComboBoxItem are a StackPanel control, so next I get a reference to it in the sp variable.

Next, I suppose I could iterate of the Children of the StackPanel, but since I know that the TextBlock I want is the first child, I’ll simply reference it directly as element zero and return it to the block variable.

Finally we can get to the actual text for the row the user picked. We can simply reference the TextBlock’s text property in the message box. When the app is run, you should see these results:

wpf041

The same techniques I use here would also be applicable to the ListBox we’ve seen previously, simply replace ComboBoxItem with ListBoxItem.

The WPF ComboBox can be quite useful for providing a compact way for users to select complex items.

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Downloading a Virtual PC Image of Visual Studio 2008 Beta 2

During last week’s WPF class, several of my coworkers expressed an interest in using the 2008 edition to experiment with WPF. They were concerned installing the beta on their production box could damage their boxes, even though in theory part of the beauty of .Net is the ability to run multiple versions of the framework side by side.

To alleviate those fears, Microsoft has provided a Beta of 2008 already in a ready to run Virtual PC. First, you’ll need to have Microsoft Virtual PC 2007 installed on your box. If you don’t, you can grab a copy from

http://www.microsoft.com/downloads/details.aspx?familyid=04D26402-3199-48A3-AFA2-2DC0B40A73B6&displaylang=en

(Even though the instructions indicate it should work with VPC 2004 SP1 or Virtual Server, I haven’t tried it with them. Virtual Server should be fine, but I would highly suggest upgrading your VPC 2004 to 2007 if you haven’t done so already, there’s lots of nice new features that make it worth the effort.)

Now you can grab the 2008 image. You will actually need two sets of files, the base image and the 2008 Beta 2 image. You can download the 2008 Beta 2 from

http://www.microsoft.com/downloads/details.aspx?FamilyID=3b72271c-e996-4989-898d-72d684966ce6&DisplayLang=en

The download is in the form of 7 files, the first is an exe and the rest are rar files. Download all 7 to a folder and run the exe, and it will combine all 7 to create the virtual pc image.

Make sure to read all of the instructions on this page! The user ID and password to login to the virtual image, along with a link to the needed base image, are contained in the instructions!

Now you need the Orcas base image. If you read through the instructions you saw the link to the compressed file, right above the user id / password. Right click on the link and “Save As…” to the same folder where you saved the other items. Run it to uncompress the base image.

OK, in a folder you should now have OrcasBeta2_VSTS.vmc, OrcasBeta2_VSTS.vhd, Base01.vmc, and Base02.vhd. I also copied the user id and password from the above linked page and saved it in a text file called “Orcas Beta 2 user id and password.txt”, just so I could remember it easily.

When you login, it tells you that the password expries today, and asks if you wish to change it. I’ve always just said no, and it seems to work fine, but you are welcome to change it if you want.

When you shut down the Virtual PC, you will be prompted first for why you are shuting down. This is a Windows Server 2003 prompt, I just select “Other (Planned) under the option and put an ‘x’ for the comment. Once you do the OK button will be enabled.

Next, Virtual PC prompts you, to see if you want to commit your changes or abandon them. If you select “Commit changes to the virtual hard disk”, any changes you made will be saved and ready for next time. If you choose “Delete undo disk changes”, everything you did during that session will be lost forever.

Since it’s just a virtual image, I usually pick commit, but if you have really hosed things up you might want to know about the Delete option.

All of the software I’ve mentioned here is free, so there’s no reason why you can’t run this at home, even if you don’t have an MSDN subscription. Be warned, although Microsoft hasn’t specified a date I would think the image will expire not long after the release of the full Visual Studio 2008 product.

Using the virtual image will allow you to experiment with WPF, as well as the new 2008 features in a safe, risk free environment.

Note: If you want to use Visual Studio 2005 to write WPF (as well as other .Net 3.0 projects), I have documented the bits you need to download in this post:

https://arcanecode.wordpress.com/2007/08/20/installing-the-wpf-bits/

Scrolling in WPF

I realized in my last post on WPF ListBoxes I overlooked a basic concept, how to make the ListBox scroll when there’s more items than can fit. Let’s return to the code from Monday, but resize the Window so only the top two pictures show. Running the app doesn’t change anything, the top two still show with no way to scroll down.

It turns out this is quite easy to fix, in several ways. First, many controls such as the containers (WrapPanel, for example) or listing controls (ListBox, TreeView to name two) have built in ScrollBars. The reason they did not appear in our example is because the ListBox was inside a StackPanel, and the StackPanel extended below the window edge. As such the ListBox didn’t realize it wasn’t fully displayed.

The simple way to fix then, is to remove the StackPanel and have the ListBox be the only thing on the window. As soon as we do, Vertical Scrollbars automatically appear.

wpf037

Next, if we wanted to, we could wrap the entire panel in <ScrollViewer> tags. ScrollViewer is a XAML tag that will take whatever is inside and move with scrollbars, as needed. What you need to understand though is you’re moving the entire StackPanel, not just the ListBox.

To demonstrate, let’s add a text block to stack panel, just above the list box.  

  <ScrollViewer>

    <StackPanel>

      <TextBlock Background=LightBlue>Pick A Row</TextBlock>

      <ListBox Name=lbxCool>

      <!– ListBoxItems omitted for brevity –>

      </ListBox>

    </StackPanel>

  </ScrollViewer>

Now if you run the program, you’ll see the text block scrolls up with the list box.

wpf038

Note the text block has indeed scrolled up off the screen.

The best way to solve this would be to move the contents to a Grid. The grid sizes correctly take up the space, and allows the list box to automatically display it’s scrollbars.  

  <Grid Name=myGrid >

    <Grid.RowDefinitions>

      <RowDefinition Height=20></RowDefinition>

      <RowDefinition></RowDefinition>

    </Grid.RowDefinitions>

    <TextBlock Grid.Row=0 Background=LightBlue>Pick A Row</TextBlock>

    <ListBox Name=lbxCool Grid.Row=1>

      <!– ListBoxItems omitted for brevity –>

    </ListBox>

  </Grid>

wpf039

If you need horizontal scrollbars, you can add the  ScrollViewer.HorizontalScrollBarVisibility=Visible” tag to the ListBox declaration.

And there you go, a few ways you can add scrolling to your ListBox, or to an entire container using the <ScrollViewer>.

WPF ListBox

Another old and faithful control that has made the transition to WPF is the ListBox. It’s pretty simple to create a ListBox, and load some values into it.

      <ListBox>

        <ListBoxItem>Item 1</ListBoxItem>

        <ListBoxItem>Item 2</ListBoxItem>

        <ListBoxItem>Item 3</ListBoxItem>

      </ListBox>

Of course the ListBox isn’t much good if you can’t get the value out of it. To do that we’ll have to add a few things.

      <Button Name=ShowSelected Click=ShowSelected_Click>Show Selected</Button>

      <ListBox Name=lbxDemo>

        <ListBoxItem>Item 1</ListBoxItem>

        <ListBoxItem>Item 2</ListBoxItem>

        <ListBoxItem>Item 3</ListBoxItem>

      </ListBox>

 

Here I added a button that would show which item was selected, then I had to give the ListBox a name we could refer to. Following techniques I’ve previously laid out (https://arcanecode.wordpress.com/2007/09/07/adding-wpf-controls-progrrammatically/) I added a click event for the button.

Now, you might think you could just enter something like

      MessageBox.Show(“You Selected “ + lbxDemo.SelectedValue);

And get a message back. But instead what you get is:

 

wpf033

This is because the SelectedValue is actually a ListBoxItem, and not a value. Instead you need to get the content of the ListBoxItem thusly:  

      ListBoxItem lbi = (lbxDemo.SelectedItem as ListBoxItem);

      MessageBox.Show(“You REALLY selected “ + lbi.Content.ToString());

Now you’ll see:

wpf034

Note that you’re not just restricted to ListBoxItems. I could, for example use checkboxes:

      <ListBox Name=lbxCheckMe>

        <CheckBox>Item 1</CheckBox>

        <CheckBox>Item 2</CheckBox>

        <CheckBox>Item 3</CheckBox>

        <CheckBox>Item 4</CheckBox>

      </ListBox>

wpf035

Like other controls, you can stack other controls inside the contents of a ListBoxItem. Let’s get a little fancy, and create a list box with both text and images.

      <ListBox Name=lbxCool>

        <ListBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Anna</TextBlock>

            <Image Source=D:\Presentations\100Anna.jpg Height=100 />

          </StackPanel>

        </ListBoxItem>

        <ListBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Raven</TextBlock>

            <Image Source=D:\Presentations\100Rave.jpg Height=100 />

          </StackPanel>

        </ListBoxItem>

        <ListBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Ammie</TextBlock>

            <Image Source=D:\Presentations\100Ammie.jpg Height=100 />

          </StackPanel>

        </ListBoxItem>

        <ListBoxItem>

          <StackPanel Orientation=Horizontal>

            <TextBlock Width=100>Kids</TextBlock>

            <Image Source=D:\Presentations\100Kids.jpg Height=100 />

          </StackPanel>

        </ListBoxItem>

      </ListBox>

    </StackPanel>

(Note you can use any images, I used a few of my kids and wife.) The result is this:

wpf036

This covers some basics on using a ListBox, enough to get you started with your own lists.

Adding WPF Controls Progrrammatically

On August 29th I wrote a posting about the StackPanel (https://arcanecode.wordpress.com/2007/08/29/stacking-the-deck-with-the-wpf-stackpanel/). A commentor asked “how do you add controls programmatically?” Good question, and it turns out to be quite easy.

Let’s create a sample app, and add a new window. I named mine AddControls. Here’s the XAML:

<Window x:Class=WPFSample001.AddControls

    xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation

    xmlns:x=http://schemas.microsoft.com/winfx/2006/xaml

    Title=AddControls Height=114 Width=212

    >

  <StackPanel Name=splMain>

    <Button Name=btnAddMore Click=btnAddMore_Click>Add Another</Button>

  </StackPanel>

</Window>

And here’s what it looks like:

wpf029

A few things I’d like to point out. I’ve given a name to the StackPanel, so it can be manipulated in our C# code. I also added a handler for the Click event for the button, btnAddMore_Click. I also named the button, although it really wasn’t necessary for this sample.

OK, make sure to build the app so intellisense will work, then let’s jump to the C# code behind. (You may get an error about the click handler for the button not being found, that’s fine just ignore it.)

First, we’ll create an event handler for the button, passing in the sender and routed event args, like I discussed yesterday (https://arcanecode.wordpress.com/2007/09/05/the-wpf-button/) . Then, all we have to do is create a button control and add it to the children collection of the StackPanel, like so: 

    public void btnAddMore_Click(object sender, RoutedEventArgs e)

    {

      System.Windows.Controls.Button newBtn = new Button();

      newBtn.Content = “A New Button”;

      splMain.Children.Add(newBtn);

    } 

 

Note in this example I used the fully qualified System.Windows.Controls, I did that just to be explicit where the Button came from. After a new button is created, I set it’s Content property, which in this case will be the text on the button.

In the final line, I add it to the children collection of the StackPanel. When you run it, and press the “Add Another” Button, you will see:

wpf030

Now we have a new problem. We’ve added a button to the StackPanel, but clicking on it does no good as we haven’t tied it to an event handler. Turns out that’s pretty easy too.

    public void btnAddMore_Click(object sender, RoutedEventArgs e)

    {

      System.Windows.Controls.Button newBtn = new Button();

      newBtn.Content = “A New Button”;

      newBtn.Click += new RoutedEventHandler(newBtn_Click);

      splMain.Children.Add(newBtn);

    }

 

What I did was use a delegate. I added a new RoutedEventHandler and tied it to the click event. The code for the event is in a method named newBtn_Click:

    private void newBtn_Click(object sender, RoutedEventArgs e)

    {

      MessageBox.Show(“New Button Clicked!”, “I got pressed.”);

    }

 

The signature for the event handler has to match the signature for a Click event, since that’s what we’re routing to. Here, all I do is display a message box just so you can see something got done. Run it again and press the Add Another button, and the “A New Button” should appear. Press the new button and you should see a message box.

wpf031

Finally, I want to be clear you can use this technique to add any sort of control. Here I’ve added a Label as well as a button:

    public void btnAddMore_Click(object sender, RoutedEventArgs e)

    {

      System.Windows.Controls.Button newBtn = new Button();

      newBtn.Content = “A New Button”;

      newBtn.Click += new RoutedEventHandler(newBtn_Click);

      splMain.Children.Add(newBtn);

 

      System.Windows.Controls.Label newLbl = new Label();

      newLbl.Content = “Hi Mom!”;

      splMain.Children.Add(newLbl);

    }

wpf032

I could have created the entire form in C# (or VB.Net) code, adding the StackPanel directly to the “this” object. However, that gets a bit laborious, and I wouldn’t recommend it as a general practice.

WPF Text Controls

WPF Supports several types of text controls for displaying text on your WPF Windows. First is the TextBlock. The text block is very simple, it just displays whatever text you enter on the window. A very basic control for display of titles and what not.

Next up the food chain is the Label. The Label has several advantages over the TextBlock. First, you can change the contents of a label at run time. Let’s take this simple example. First, let’s add a Label to the Button window we created yesterday. In case you missed it, here’s the XAML:

<Window x:Class=WPFSample001.ButtonWindow

    xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation

    xmlns:x=http://schemas.microsoft.com/winfx/2006/xaml

    Title=Buttons Height=83 Width=194

    >

  <StackPanel>

    <StackPanel>

      <Button Click=Baby_Click>Click Me Baby!</Button>

      <Label Name=lblMyLabel>Before the click</Label>

    </StackPanel>

  </StackPanel>

</Window>

Notice we’ve added a Name property to the Label. This is so we can address it by a specific name within our C# code. After you add the Label here’s an important step: build the application (Build, Build Solution on the menus). You need to do the build so the control will show up in intellisense once you get to the C# window. You can still write the code and make it work, but the intellisense makes it so much easier it’s worth the few seconds to run a build.

OK, you’ve built the app, go to the C# code behind. Locate the event handler for Baby_Click and insert a line to alter the content of the label:

    private void Baby_Click(object sender, RoutedEventArgs e)

    {

      MessageBox.Show(“Hi There!”,“Baby was clicked!”);

    }

If you’ve done traditional WinForms coding in the past, this syntax should look pretty familiar to you. Running the app will produce the expected result. Here’s the before you click:

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And here’s shot after you click the button:

wpf025 

If you remember the “old days” of WinForms program, you may remember it was possible to use a label as an access key for a textbox. You can still do this with WPF, it just takes a little code. Let’s create a new form, call it LabelForm.

To the LabelForm, add a grid with two rows and two columns, then add two labels and two text boxes. Here’s a sample:

<Window x:Class=WPFSample001.LabelWindow

    xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation

    xmlns:x=http://schemas.microsoft.com/winfx/2006/xaml

    Title=Label Window Height=95 Width=252

    >

  <Grid>

    <Grid.RowDefinitions>

      <RowDefinition></RowDefinition>

      <RowDefinition></RowDefinition>

    </Grid.RowDefinitions>

    <Grid.ColumnDefinitions>

      <ColumnDefinition Width=*></ColumnDefinition>

      <ColumnDefinition Width=2*></ColumnDefinition>

    </Grid.ColumnDefinitions>

    <Label Target={Binding ElementName=FirstBox} Grid.Row=0 Grid.Column=0>_First Box</Label>

    <Label Target={Binding ElementName=SecondBox} Grid.Row=1 Grid.Column=0>_Second Box</Label>

    <TextBox Name=FirstBox Grid.Row=0 Grid.Column=1 />

    <TextBox Name=SecondBox Grid.Row=1 Grid.Column=1>

    </TextBox>

  </Grid>

</Window>

Notice two things. First, we had to give our textboxes a name, via the Name property. Second is the Target property. Inside the property you see curly braces with the word Binding. This is an example of a Markup Extension. Markup Extensions are special WPF classes that are created by the XAML Parser and bound to the item (in this case a Label) we are creating. The items with equal signs, such as ElementName in this example, are named parameters for the Binding class.

I realize that’s a lot of concept in a little space, it might be easier to simply thing of the items in curly braces as a way to define special functionality within WPF.

In this example, the Binding extension binds the label to the textbox passed in the ElementName. When you run the above example, and press the alt key you will see the F (in First) and S (in Second) become underlined.

wpf026 

Pressing F or S will jump you between the text boxes. It’s a bit hard to visualize, but try running the code yourself and you’ll see what I mean.

There’s one more text control I want to mention, the ToolTip. The easy way to create a ToolTip is to simply add it as an item when you create a control. Let’s add a ToolTip to the text boxes.

    <TextBox Name=FirstBox Grid.Row=0 Grid.Column=1 ToolTip=The First Box/>

    <TextBox Name=SecondBox Grid.Row=1 Grid.Column=1 ToolTip=Second Box />

As you can see all I had to do is add a ToolTip= and it’s added.

wpf027 

You can also declare the tooltip as a content item of the main control, using this syntax:

    <TextBox Name=SecondBox Grid.Row=1 Grid.Column=1 >

      <TextBox.ToolTip>

        Second Box

      </TextBox.ToolTip>

    </TextBox>

Why use this second way? Well remember, since it’s content you can get pretty complex with what you declare. Try this out:

    <TextBox Name=SecondBox Grid.Row=1 Grid.Column=1 >

      <TextBox.ToolTip>

        <StackPanel>

          <Label Background=Red Foreground=White>Help Title</Label>

          <TextBlock>This is some descriptive text for the tooltip that tells what it does.</TextBlock>

        </StackPanel>

      </TextBox.ToolTip>

    </TextBox>

Run the app and hover over the second box, and you should see something like this:

wpf028 

Now you begin to gleam a little of the power of WPF, the ability to combine controls and create complex interfaces quickly and easily.

The TextBlock, Label, and ToolTip are the three text controls you can use to display info to your users.

Breaking news: Silverlight 1.0 Released!

Hot off the presses, Microsoft has released Silverlight 1.0! For those unfamiliar with Silverlight, it’s a lightweight add-in that works with most browsers. It allows you to display incredibly rich content in the browser. Version 1.0 uses AJAX libraries to handle multimedia content, games and more.

Read the Microsoft Press Release at:

http://www.microsoft.com/presspass/press/2007/sep07/09-04SilverlightPR.mspx

There is an interview with Scott Guthrie on Channel 9, you can see it here:

http://channel9.msdn.com/showpost.aspx?postid=339594

You can download Silverlight and learn more about it at the Silverlight site:

http://silverlight.net/Default.aspx

or the Microsoft page (slightly different content)

http://www.microsoft.com/silverlight/

Scott Guthrie has a really informative post on his blog:

http://weblogs.asp.net/scottgu/archive/2007/09/04/silverlight-1-0-released-and-silverlight-for-linux-announced.aspx 

If you want to see an example of a Silverlight site, visit the Alabama Code Camp site at:

http://www.alabamacodecamp.com/home.html

Sweet.