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ByMel

WPF: Setting a Type Specific Property Value

While XAML in WPF is probably the most powerful GUI development architecture I’ve ever used and by far my favorite, there’s still a few little tasks here and there that I just scratch my head trying to figure out.

This is probably due to my limited knowledge of XAML and how to use it properly, so until I get it all mastered I’m forced to use lines of DuctTape to get some of the results I want.

Here’s my most recent hack job. If you look at the XAML below you’ll notice that I’m making use of the Tag property of the button. This is just an example, but in real life there’s actually quite a few valuable uses for Tag.

<button content="Am I the right button?" tag="False" click="Button_Click"></button>
<button content="Am I the right button?" tag="True" click="Button_Click"></button>
<button content="Am I the right button?" tag="False" click="Button_Click"></button>

So in this example the user needs to click the right button. The right button is indicated by its tag property. In this case the second button is the one that works, right?

Which button is it?

Not exactly.

The code to handle this situation would look something like this:

private void Button_Click(object sender, RoutedEventArgs e)
{
    var sourceBtn = sender as Button;
 
    bool isRight = (bool)sourceBtn.Tag;
}

Since Tag is defined as an object and I’m binding it to “False” in my XAML I thought this code would work out just fine, but it doesn’t.

The problem is Tag gets populated with a string instead of a boolean. That’s interesting, after all why shouldn’t it? How is XAML supposed to know that what I wanted to set to Tag is the boolean value False? It doesn’t.

So I had to write my XAML in such a way that it knew without a doubt that I was using a boolean value.

The first thing in accomplishing this was to include the System namespace in my XAML file, like so:

xmlns:system="clr-namespace:System;assembly=mscorlib"

Then I could declare my Tag property full out giving it a system:Boolean for its value.

<button content="Am I the right button?" click="Button_Click">
	<button.tag>
		<system:boolean>False</system:boolean>
	</button.tag>
</button>
<button content="Am I the right button?" click="Button_Click">
	<button.tag>
		<system:boolean>True</system:boolean>
	</button.tag>
</button>
<button content="Am I the right button?" click="Button_Click">
	<button.tag>
		<system:boolean>False</system:boolean>
	</button.tag>
</button>

And that’s it, it works! Yay!

But man, it really is ugly. Does anyone know of a cleaner, better way to accomplish the same thing? I would love to learn something new!

ByMel

C#: Detect If You’re Running on the Server

If you ever need to detect whether your code is running on the machine that you’re talking to through IP (a server application for example), and you know the IP address for the remote machine, then this code may come in handy. It was originally written by my buddy Erin for a project we both worked on.

using System.Net;

private bool CheckIfServer(IPAddress serverIP)
{
    // Get all addresses assigned to this machine
    List ipAddresses = new List();
    ipAddresses.AddRange(Dns.GetHostAddresses(Dns.GetHostName()));

    // If desirable, also include the loopback adapter
    ipAddresses.Add(IPAddress.Loopback);

    // Detect if this machine contains the IP for the remote server
    // Note: This uses a Lambda Expression, which is only available .Net 3.x
    return ipAddresses.Exists(i => i.ToString() == serverIP.ToString());
}

If you don’t know the IP Address for your remote server you can easily get it using the server’s host name like this:

IPAddress[] addresses = Dns.GetHostAddresses("remote_host_address");

This returns an IPAddress[] which includes all the resolved addresses for that host.

ByMel

C#: Lower Case All XML Tags with Regex

Sometimes when accepting an XML document from an uncontrolled source using Linq to XML, it’s useful to convert all tags and attributes to lower case before processing the XML. This is because Linq to XML is case-sensitive and you can’t always rely on the program producing the XML to follow your casing standard for elements and attributes.

So here’s a quick and dirty single line of code that will accomplish just this in C# using a regular expression:

Regex.Replace(
    xml, 
    @"<[^<>]+>",
    m => { return m.Value.ToLower(); }, 
    RegexOptions.Multiline | RegexOptions.Singleline);

And here’s that functionality all nice and wrapped up inside of an extension for XElement:

public static class XElementExt
{
    public static string LowerCaseTags(string xml)
    {
        return Regex.Replace(
            xml,
            @"<[^<>]+>",
            m => { return m.Value.ToLower(); },
            RegexOptions.Multiline | RegexOptions.Singleline);
    }
}

Note: The Regex class is defined in System.Text.RegularExpressions

Here’s an example of the resulting affect.

Before:

<ELEMENT>
    <ChildTag>
        <inner>This text Will not Be Harmed!</inner>
    </ChildTag>
</ELEMENT>

After:

<element>
    <childtag>
        <inner>This text Will not Be Harmed!</inner>
    </childtag>
</element>

You’ll notice that with this method all text within element tags is converted to lower case. This means that attribute values will lose any special casing they may have had, which may or may not be a problem for what you’re doing.

ByMel

C#: Set File Type Association

While searching for some simple C# code to set the program and icon associated with a file type in Windows I ran across these beautiful functions that illustrate how to accomplish this by using the registry.

All credit goes to cristiscu (source).

Here’s the code:

using Microsoft.Win32;
using System.Runtime.InteropServices;

public class FileAssociation
{
    // Associate file extension with progID, description, icon and application
    public static void Associate(string extension, 
           string progID, string description, string icon, string application)
    {
        Registry.ClassesRoot.CreateSubKey(extension).SetValue("", progID);
        if (progID != null && progID.Length > 0)
            using (RegistryKey key = Registry.ClassesRoot.CreateSubKey(progID))
            {
                if (description != null)
                    key.SetValue("", description);
                if (icon != null)
                    key.CreateSubKey("DefaultIcon").SetValue("", ToShortPathName(icon));
                if (application != null)
                    key.CreateSubKey(@"Shell\Open\Command").SetValue("", 
                                ToShortPathName(application) + " \"%1\"");
            }
    }

    // Return true if extension already associated in registry
    public static bool IsAssociated(string extension)
    {
        return (Registry.ClassesRoot.OpenSubKey(extension, false) != null);
    }

    [DllImport("Kernel32.dll")]
    private static extern uint GetShortPathName(string lpszLongPath, 
        [Out] StringBuilder lpszShortPath, uint cchBuffer);

    // Return short path format of a file name
    private static string ToShortPathName(string longName)
    {
        StringBuilder s = new StringBuilder(1000);
        uint iSize = (uint)s.Capacity;
        uint iRet = GetShortPathName(longName, s, iSize);
        return s.ToString();
    }
}

And here’s how you’d use it:

if (!FileAssociation.IsAssociated(".ext"))
   Associate(".ext", "ClassID.ProgID", "ext File", "YourIcon.ico", "YourApplication.exe");

A couple caveats to this code that I’ve noticed:

  1. The second parameter passed to Associate() can be any string you’d like to use to represent your program in the registry, just make sure you’re consistent with it.
  1. ToShortPathName() will return an empty string if the file path you pass it doesn’t exist, i.e. if you pass it a path to an icon file that doesn’t exist it won’t work.
  1. IsAssociated() will return true if the file extension is associated with any program, not just yours. If you want to be specific about it checking whether it’s associated with your program, then just check whether it’s default key is set to your programs ProgID.
ByMel

New Addition to Family

I’m so excited! On Sunday, December 21st at 2:52 pm my wonderful wife gave birth at our home to a beautiful baby boy! We never had an ultra sound or anything so he was a happy surprise.

We’ve since decided to name him Michael Woolley Green since Michael just seems right and Woolley is in honor of his maternal heritage, being decended from Lorin and John Woolley.

Anyway, he’s awesome. Here are some pictures:

Michael and Mother

Michael and Mother

McKenzie with her new brother Michael

McKenzie with her new brother Michael

Big Yawn...

Big Yawn...