I Learned It Online

WPF: How to set the SelectedValue on Data Bound ComboBox

Joe — Thu, 26 Jun 2008 16:46:23 +0000

Most of the time when you have a form, you will have some combo boxes, and some list boxes. If you are editing an existing item, most likely you are going to want to have these items display the currently selected value. So we are going to populate a form with some contacts and provide a combo box of companies that they could work for. When we select an individual contact from our list, we would expect the combo box to change and show the company the contact currently is associated with.

We want to start by creating a couple of objects, 1 for company details and another for our contacts. So start out be creating a new class and you can call it Company.

Company.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Collections.ObjectModel;namespace MyContacts
{
public class Company : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void Notify(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
} int pId;
public int Id
{
get { return pId; }
set
{
if (pId == value)
return;
pId = value;
Notify(”Id”);
}
} string pName;
public string Name
{
get { return pName; }
set
{
if (pName == value)
return;
pName = value;
Notify(”Name”);
}
}

public Company(int id, string name)
{
Id = id;
Name = name;
}
}

public class Companies : ObservableCollection { }

public class CompanyKeeper
{
public Companies LoadCompanies()
{
Companies companies = new Companies();
companies.Add(new Company(1, “Microsoft”));
companies.Add(new Company(2, “Symantec”));
companies.Add(new Company(3, “Oracle”));
companies.Add(new Company(4, “Apple”));
return companies;
}
}
}

We also need a 2nd class for the Contacts.

Contact.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Collections.ObjectModel;namespace MyContacts
{
public class Company : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void Notify(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
} int pId;
public int Id
{
get { return pId; }
set
{
if (pId == value)
return;
pId = value;
Notify(”Id”);
}
} int pCompanyId;
public int CompanyId
{
get { return pCompanyId; }
set
{
if (pCompanyId == value)
return;
pCompanyId = value;
Notify(”CompanyId”);
}
}

string pFirstName;
public string FirstName
{
get { return pFirstName; }
set
{
if (pFirstName == value)
return;
pFirstName = value;
Notify(”FirstName”);
}
}

string pLastName;
public string LastName
{
get { return pLastName; }
set
{
if (pLastName == value)
return;
pLastName = value;
Notify(”LastName”);
}
}

public Contact(int id, int companyId, string firstName, string lastName)
{
Id = id;
CompanyId = companyId;
FirstName = firstName;
LastName = lastName;
}
}

public class Contacts : ObservableCollection { }

public class ContactKeeper
{
public Contacts LoadContacts()
{
Contacts contacts = new Contacts();
contacts.Add(new Contact(1, 1, “Bill”, “Gates”));
contacts.Add(new Contact(2, 1, “Steve”, “Ballmer”));
contacts.Add(new Contact(3, 2, “John”, “Thompson”));
contacts.Add(new Contact(4, 3, “Lawrence”, “Ellison”));
contacts.Add(new Contact(5, 4, “Steve”, “Jobs”));
return contacts;
}
}
}

The SelectedValuePath is the Property from the Company object and the SelectedValue is the Id in the Contact object. Remember we called ours CompanyId. The 2 key items that you need to be sure to set in order to have the combobox display the currently selected company when you select a contact is to set

SelectedValuePath - This is the Property from the ItemsSource. In our case of using the Company object, it is the Id field.
SelectedValue - This is the CompanyId Property from our Contact object.

Windows1.xaml

xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation“
xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml“
xmlns:local=”clr-namespace:MyContacts”
Title=”Window1″ Width=”300″ Height=”275″>

x:Key=”Contacts”
IsAsynchronous=”True”
ObjectType=”{x:Type local:ContactKeeper}”
MethodName=”LoadContacts”/>

x:Key=”Companies”
ObjectType=”{x:Type local:CompanyKeeper}”
MethodName=”LoadCompanies”/>

,

Grid.Row=”3″ Grid.Column=”1″ SelectedValuePath=”Id” SelectedValue=”{Binding Path=CompanyId}”
ItemsSource=”{Binding Source={StaticResource Companies}}” ItemTemplate=”{StaticResource CompanyDataTemplate}” />

WPF Binding from the CornerRadius of a Border

Joe — Fri, 09 May 2008 21:25:54 +0000

Ok, after posing this question over at .NET Blog it took me all of about 30 seconds to realize what I needed to do.

Is it possible to do Binding on separate corners of the CornerRadius. I would like to have a slider that the top corners on the Border increase/decrease radius as the slider is moved. But I don’t want the bottom to corners to be affected.

I had used the tutorial over at Martin Grayson: Adventures of a ‘Designer’ to create a glass button for a project I am working on. This was a great starting point for my buttons, but there were a few things I needed to modify. I am only going to show you how I was able to bind to a slider to change the radius of the button.

The first thing I did was create the control template, notice though that where the corner radius is, I have binded it to a slider that I have added. But on the one corner, the corners originally were set to 4,4,0,0, which will mean that if we use the value from the slider, it will end up looking looking distorted like Figure 1.

Figure 1

Here is the converter that I used which returns the radius as a string and leaves the bottom corners set to 0.

public class CornerRadiusConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
string rad = value.ToString();
return rad + “,” + rad + “,0,0″;
}

public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return “”;
}
#endregion
}

Figure 2 shows the buttons after the converter.

Figure 2

If you had to pick 1 accessory for your EeePC

Joe — Fri, 02 May 2008 22:19:22 +0000

I am not usually in the habit of recommending anything, but I bought the Targus PA248U Tornado Notebook Chill Pad 2 weeks ago. I love my little Eee, but it gets pretty hot, so I wanted to try and keep it cooler, and hopefully in the process would extend the life of it. The PS248 is a little bigger than the Eee, but compliments it really nicely. It still is very easy to carry both in 1 hand and not feel like i was lugging around a 5 pound over sized notebook.
If you could only afford 1 accessory, I would recommend the P248.

WPF IDataErrorInfo and DataBinding

Joe — Thu, 24 Apr 2008 18:09:35 +0000

This is by far the best example of IDataErrorInfo and DataBinding that any beginner can easily grasp.

Why Use Linux?

Joe — Mon, 14 Apr 2008 15:07:00 +0000

The other day I got into a somewhat heated discussion about why Linux is a viable alternative desktop OS. Despite my best efforts, I was unable to move the other side past the rhetoric and myths that seem to surround Linux. It is because of this discussion that I am writing this…as a way to give accurate information.
read more | digg story

How to create a EeePCLinuxOS LiveUSB with VirtualBox

Joe — Mon, 14 Apr 2008 02:21:47 +0000

I was having all types of trouble trying to create a bootable CD from the eeePCLinuxOS iso file, so I decided to try installing from the iso directly to a USB flash drive. I am running a Windows Vista PC and decided I would try using VirtualBox to boot the iso and attach the USB drive. This also helps everyone by not creating an additional CD that will shortly end in the trash.

What you will need.

VirtualBox
eeePCLinuxOS ISO

Once you have installed VirtualBox, you are ready to create a new virtual machine.

You need to give the VM a name. I like to name mine according to the OS that is being installed. You can use any name you would like, just remember to make it unique.

At the next step, you will need to define the amount of RAM you would like to use. I changed mine from the default 256 to 1024, which is 1gig of memory.

If you want to install to a virtual hard drive, you will need to add a new hard drive or use and existing one. I didn’t create one as I only want to be able to create a LiveUSB flash drive.

This will bring you to the final summary of the VM you are creating. This is not the final step though, you still need to point the VM to the ISO file and enable USB in the VM.

Once you have been returned to the main VirtualBox screen, select the new VM and click the Settings button. From there select the CD/DVD ROM option and select to Mount CD/DVD Drive and use the ISO option. Browse to the eeePCLinuxOS ISO file you downloaded earlier.

You will need to insure that you have enabled USB support or none of the following steps will work. If you select the little USB plug on the right hand side, the one with the little green (+)plus sign. This will allow you to select the USB device to use.

The rest of the install has already been covered in other places, but I will show some screenshots to help you along the way.

Since we are installing to the USB device, be sure NOT to select the Solid State Device. You will use this later to install to the Eee.

When prompted for the installation drive, you may only have one option. If you have multiple options, ensure that you select the USB drive you want to use for eeePCLinuxOS.

You can select whatever option you would like. I had a flash drive I was using only for installing different distros to my Eee. Therefore, I erased the content of the drive.

I left out a number of steps but once you have completed the install, you should have a bootable USB flash drive.

How to use USB727 with Pendrive Linux

Joe — Sun, 06 Apr 2008 16:30:26 +0000

I was extremely surprised with how easy it was to configure my Verizon EVDO connection on the USB727 from Pendrive Linux. You will want to start with the USB727 unconnected to your PC.

I am not positive that you have to do this but with Ubuntu you have to use the sudo command when entering all of the following commands, so I went ahead and switched to root.
$ su
You should be prompted to enter the root password, which on the default install is root.

Unload the usbserial serial driver.
# modprobe -r usbserial

Insert your USB727 and load the driver for the device. I am using the USB727, therefore my command looked like below. If you are using a different device, see the Sprint Mobile Broadband document to find your vendor and product id. Simply select the Linux option from the dropdown box and you can then use the PDF.
# modprobe usbserial vendor=0x1410 product=0x4100

# dmesg|grep -i ttyUSB
Should give you something similar to below.
[ 1863.832000] usb 2-1: generic converter now attached to ttyUSB0 [ 1863.836000] usb 2-1: generic converter now attached to ttyUSB1 [ 1863.836000] usb 2-1: generic converter now attached to ttyUSB2 [ 1863.840000] usb 2-1: generic converter now attached to ttyUSB3

Now you are ready to setup the dialup connection. Navigate to the `Configure Your Computer` menu option as seen in the screenshot below.

This will give you the Control Center panel. We want to setup a new network interface.

Select the Analog telephone modem (POTS) option.

For the modem configuration, I only had the option for Manual choice. If you get any additional options, select appropriately.

Select /dev/ttyUSB0

If you are using this, most likely you are in the United States. You will have to select the Unlisted option.

Configure the login information. I was not able to find any password details so I simply used vzw for the password and it seemed to work fine.

For the dialup IP parameters, you should select automatic.

DNS settings should be set to automatic unless you have DNS servers that you would prefer to use. I have a few friends who only ever use specific DNS servers.

The gateway should be set to automatic.

I like to allow users to manage the connection. The defaults are all unchecked.

Finally you can connect to the internet. It took some time to complete the connection, but ever since it has worked seemlessly.

I used SpeedTest.net to test my speed and was getting 490kbps dowload and 209kbp upload. This is a vast improvement from using the wireless connection at the hotel I am at. There most of the time the connection would drop about every 15 minutes depending on the time of day.

If anyone knows of an app that will show the connection speeds, please comment below.

How to create a generic method to get selected value from WPF ListBox Control

Joe — Sat, 05 Apr 2008 22:38:47 +0000

On a recent project, I had several listbox controls and needed to pass values to a web service. Since all my listboxs used the same template, I wanted a generic method to handle the events.

Start by creating a new project named ListBoxDemo in Blend or Visual Studio. I use V# 2008 Express for my projects and prefer starting my projects there.

Add a new class file to your project and name it Contact.cs

using System;
using System.Collections;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Text;

namespace ListBoxDemo
{
    public class Contact : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void Notify(string propertyName)
        {
            if (this.PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

        int pID;
        public int ID
        {
            get { return this.pID; }
            set
            {
        if (this.pID == value)
                    return;
            this.pID = value;
            Notify(”ID”);
            }
        }

        string pFirstName;
    public string FirstName
        {
            get { return this.pFirstName; }
            set
            {
                if (this.pFirstName == value)
                    return;
                this.pFirstName = value;
                Notify(”FirstName”);
            }
        }

        string pLastName;
        public string LastName
        {
            get { return this.pLastName; }
            set
            {
                if (this.pLastName == value)
                    return;
                this.pLastName = value;
                Notify(”LastName”);
            }
        }

        public string Name
        {
            get { return this.pFirstName + ” ” + this.pLastName; }
        }

        public Contact() { }

        public Contact(int Id, string FirstName, string LastName)
        {
            this.ID = Id;
            this.FirstName = FirstName;
            this.LastName = LastName;
        }
    }

    public class Contacts : ObservableCollection { }

    public class ContactsKeeper
    {
        Contacts pContacts = new Contacts();

        public Contacts Contacts
        {
            get { return pContacts; }
        }

        public ContactsKeeper()
        {
            // This will populate the control with data. You could use this
            // to load from a database or a webservice
            pContacts.Add(new Contact(1, “John”, “Smith”));
            pContacts.Add(new Contact(2, “Mike”, “Wallace”));
            pContacts.Add(new Contact(3, “Sally”, “Miller”));
            pContacts.Add(new Contact(4, “Albert”, “Einstein”));
        }
    }
}

On the main window that was generated when you created your project, add a reference to the namespace where the Contacts class is located. We will need to create our Data Template for our listbox. In our sample, we could add our event handler, but we will do that progammatically in our cs code file.

  xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation”
  xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml”
  xmlns:local=”clr-namespace:ListBoxDemo”
  Title=”Window1″ Height=”300″ Width=”300″>

Finally we need to add our event handler and assign it to our ListBox control. Open up the Window1.xaml.cs file.

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace ListBoxDemo
{
    ///
    /// Interaction logic for Window1.xaml
    ///
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            // find the listbox
            ListBox l = (ListBox)this.FindName(”MyListBox”);

            if (l == null)
                return;

            // add the event handler to the listbox
            l.SelectionChanged += MyListBox_SelectionChanged;
        }

        private void MyListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            // find our listbox control
            ListBox l = ((ListBox)sender);
            if (l == null)
                return;

            // find the selected listbox item
            if (l.SelectedItems.Count < = 0)
                return;

            ListBoxItem itm = (ListBoxItem)l.ItemContainerGenerator.ContainerFromIndex(l.SelectedIndex);
            if (itm == null)
                return;

            // reference the data template being used.
            DataTemplate dt = itm.ContentTemplate;

            // find the border around each listboxitem
            Border b = (Border)VisualTreeHelper.GetChild(itm, 0);

            // get the content presenter, this is the area within the control
            // that holds our content
            ContentPresenter cp = (ContentPresenter)b.Child;

            // Our datatemplate has a stackpanel with our textblocks.
            // we need to find the stackpanel
            StackPanel sp = (StackPanel)dt.FindName(”RecordStack”, cp);

            // textblock that contains our record id
            TextBlock txt = (TextBlock)sp.FindName(”RecordId”);

            // Display our record id. This is pretty worthless and
            // pretty annoying, but with this you could do something
            // a bit more useful
            MessageBox.Show(”Contact ID: ” + txt.Text);
        }
    }
}

I would love to know if anyone has an easier way to do this operation.

Some thoughts on Puppy Linux

Joe — Sat, 05 Apr 2008 16:38:19 +0000

Recently many of the Linux magazines have been doing articles on Puppy Linux. If you have been reading this blog on a regular basis, you already know that I own an ASUS eeePC. One of the main reasons I bought it was so that I could use it when I travel. There was one big flaw with my plans, I still need to carry my Dell 830 to use for work. The more I work with Windows, the more I despise it but I have to use it for work. Normally I would have just partitioned the drive and installed a Linux distro and Windows, but we are not allowed to do that any longer. A friend recommended buying a second drive and just carrying that along. I was preparing to do that when I read all the hype about PL (Puppy Linux). The first thing I did was download it and install it on a USB flash drive from my home PC. It seemed to work great and on that PC I have a standard connection. Then I decided to carry it with me to visit my family. That is when I had my first problem with it, which seems to be related to using WPA on the wireless router. But it wasn’t very important to me at the time, so I just showed off how cool PL was. Now I am on my first trip with PL and am going to share my thoughts.

Not sure why this is happening, but I can’t get Xorg to work with my laptop. I ended up using Xvesa instead, which for me seems to be fine.
Pup packages are fast and easy to download and install, but sometimes they don’t show up in the menu. No a problem if you are comfortable with the command line, but for those people coming from a Windows environment it would very discouraging.
The touchpad is too sensitive. I never use a mouse when I travel and have often had people comment on how efficient I am with the touchpad. But with Puppy, and maybe this is something with all distros, it is very difficult. As a result, I had to go buy a mouse.
Connecting to the hotel wireless network took a little bit of time to nail down, but once I did it worked great.
Changing WMs (Window Managers) was very easy. I opted to use IceWM, which has a ton of themes that are fairly easy to apply. Several of the ones available on the pup package site appear to be corrupted, but I was still able to find one I liked.
Gaim worked great for several days but then after a reboot, it would show the login process and disappear where I could not locate it.
The UI fairly plain, but completely acceptable as PL was designed to run on very old hardware. See hardware requirements.

Overall PL is very nice and has many uses. I could see value in carrying it around on a small USB flash drive or on a CD in order to recover files from a corrupted OS. If you had an old PC that wasn’t really up to par for running some of the newer OSs that are on the market, it would be a great way to get some use out of it, especially if you wanted to give that PC to someone who couldn’t afford to buy a new PC.

Linux Mint 5 - Carbon

Joe — Wed, 26 Mar 2008 17:35:01 +0000

As you can see it looks far more professional (shall I say boring?) than the theme we’re currently using. It’s all grey and squary looking but it has too huge advantages:

It looks pro.

A lot of space is gained on the screen (the widgets take much less and that leaves more space for content). In particular the difference is impressive in mintMenu and in Firefox.

Though it is all grey and square looking, I quite fancy it. I have always preferred the clean professional look myself. With the nice crisp clean corners, it is very easy on the eyes. Then you add that look to a the best distro available and you have something to brag about.