IIrrelevant

Strategies for a ViewModelLocator in MvvmLight Pt. 1

Dan Morphis — Mon, 25 Jul 2011 02:59:41 GMT

I’ve been using the MvvmLight Toolkit on a project now for several weeks. At first, the ViewModelLocator pattern the toolkit uses didn’t bother me. But after you wonder why your view can’t be located and then debug everything only to discover that you forgot to create the ViewModel in the ViewModelLocator.

I first thought about switching the ViewModelLocator to inherit from DynamicObject and using MEF to discover the VIewModel’s. A quick search lead me to discover that I’m not the only one to have that same thought

The one thing I didn’t like about using Dynamic and MEF for discovering the ViewModel was the design time experience took a big hit. Locating the ViewModel was now much more expensive at design time.

I started started doing more thinking, and wondered if I could use T4 to generate the ViewModelLocator for me. After more thought, I knew I had to be able to use T4 to generate the ViewModelLocator, heck T4MVC uses it to generate a bunch of helper classes.

Because I’m big on using IoC in my apps, I’ve also added the ability to get the ViewModel from an IoC container if the application isn’t in design mode.

There are two files that are required to make this approach work. ViewModelLocator.tt, and ViewModelLocator.settings.t4. The settings file exists so you can configure the what’s and how’s. If you use the default setup for MvvmLight, the only thing you will have to change is the IoC stuff.

To use the T4 ViewModelLocator, delete your existing ViewModelLocator.cs class in your ViewModel folder, and drop the two T4 files into your ViewModel folder. Once that happens, you will see a new icon show up in the solution explorer called “Transform All Templates.” Click that icon to have your ViewModelLocator automatically generated for you, compile and run

Download the T4 templates!

Next time, I’ll write a post about using MEF, DynamicObject and other code to dynamically locator your ViewModels to create a composable application (Wait, didn’t I just say there were performance issues? Yes, but sometimes you have to take the hit).

Please post your thoughts on all this, I would be really interested in hearing other perspectives!

Rigol DS1000 Series and Windows 7, 64 bit

Dan Morphis — Thu, 28 Apr 2011 06:54:10 GMT

I purchased my DS1052E scope several months back. After trying, and failing for days to get the “Ultrascope” software to work under Windows 7 64 bit, I gave up.

My interest was recently renewed in getting the Ultrascope software to work on my computer so i decided to give it another go. This time, I succeeded!

To save others the pain I went through, I’ll document the things I did (well, that i can remember given that I had previous failed attempts). Install the Rigol Ultrascope software.

Second, download the DS1000 Series Windows driver (note, I can’t take credit for these two files, I found them in another forum). Extract these two files, then go find the device in the Device Manager. Update the driver and point it to the directory where you extract the driver files.

Next, download the NI-VISA Run-Time Engine (v5.0.3 as of this writing). Beware, this file weighs in at 71 MB. Install the VISA runtime with the default options (you could probably get away with just installing the USB portion, but I didn’t try it).

When the NI-VISA installer finally finishes, you might be prompted to reboot. I skipped this step :-). Run the Ultrascope software, and click on Tools –> Connect to Oscilloscope. I was prompted with a list of devices, with none of it making much sense, except the first option “USB0…” I choose that option and everything worked!

CNC Hardware – Part Deux

Dan Morphis — Tue, 22 Mar 2011 06:22:21 GMT

After I re-read my last post, I realized I kind of cheesed out on the drill bit part, so I figured I would more fully flesh that part out, plus detail the opto-isolated limit switches I purchased.

Drill and Router Bits

For hole drilling, I looked at buying a kit like this one from Drill Bit City, but ultimately decided that I would just get a 10 pack of each of a few different sizes. I ended up getting #71, #70, #66 and #60 drill bits from Drill Bit City.

For milling (cutting out), I got a 10 pack of .0625 down-cut carbide bits, also from Drill Bit City.

For trace isolation, I picked up a 10 pack of 60 degree carbide “V” bits off of eBay.

Limit Switches

The purpose of the limit switch is to keep the controller software from driving any of the axis's to their physical limit and causing damage.

You can certainly run your CNC machine without limit switches, but honestly, if your going to spend a minimum of $1500 on your setup, why not spend a few more dollars (and a few input pins on your break out board) and prevent costly damage to your machine?

When I was doing research on limit switches, I was originally considering using a standard lever actuated micro-switch. But I had some questions and concerns regarding their accuracy. Over time, as a axis slams into the switch, it will deform the lever.

When a microswitch is used on say an arcade button, any imperfection or deformation of the lever will go unnoticed by the user. But in the world of CNC, accuracy and repeatability are everything.

After doing a lot of research, I stumbled upon Colin Mackenzie’s Opto-Isolated Limit Switches. Colin had the same concerns I had regarding using physical limit switches and came up with an opto-isolated switch which can be wired in an “OR” configuration.

While the opto-isolated limit switches are a little bit more expensive than a typical micro-switch (at around $2 - $2.50), at $8.50, I didn’t find the cost difference to be to great.

Next time, I’ll go into the software setup.

CNC Machine Setup

Dan Morphis — Mon, 21 Mar 2011 13:13:03 GMT

For almost 10 years I’ve wanted a CNC machine. I found plans on the internet years ago, but didn’t have any money, or the right set of tools at the time to act upon that goal.

A few weeks back, I was surfing Instructables and found instructions for a crude looking CNC based on a moving table design. That rekindled my desire to own a CNC machine.

After a lot of searching, and reading, I came across the FireBall V90 Kit from Probotix. They suckered me in with the $599 base price. In all my research, unless you were doing a crude design, you were going to spend at least 500-600 on parts and materials to build the base system so I figured this was a good price.

Hardware

I ordered my kit with pretty much everything as proposed by Probotix:

The “best” motor/driver kit
Anti-backlash X and Y nuts
RF isolated breakout board
Large enclosure
40V DC linear power supply
MDF spoil board
MeshCam Bundle

I wanted to go with the aluminum T-Slot for the spoil board, but figured I could do that upgrade later given that its a $200 upgrade. Turns out, its a good thing I waited, I found some 80/20 T-Slot on Amazon for $13.44 / 48” (~1.22 meters) section.

I will have to cut that into 18” (45.72 cm) sections and either weld them together, or bolt them to a piece of MDF making sure that the top surface is flat. Thankfully, a good friend of mine has all the tools to weld aluminum.

Router Unit

For the spindle (the cutting head) I went with a Wolfgang Engineering TB650. The TB650 is an upgrade over the TB350 which gets very high marks.

For cutting bits, I ordered a variety of bits from Drill Bit City for both hole drilling, and I went with carbide #71 down-cut carbide bits to do the actual milling of the board (cutting out from the stock).

I also ordered some 60 degree “V” bits from Carbide World so I can do PCB trace isolation.

Next time, I’ll detail my software setup.

Upgrading your installed NuGet packages to CTP2

Dan Morphis — Sun, 07 Nov 2010 20:08:09 GMT

At the Fall 2010 DevConnections keynote, Scott Guthrie demo’d NuGet (formally Nupack). After seeing how easy NuGet makes it to install project references and resolve dependencies, I had to try it!

After installing CTP1 of NuGet and installing a bunch of packages, I found out I needed the latest version (the 10-26-2010 build) in order to install some of the packages I wanted. Well, between CTP1 and the 10-26-2010 build, the NuSpec file format has changed slightly, making packages created with CTP1 and the 10-26-2010 build incompatible.

I decided to pop open a .nupkg (.nupkg the file extension of a NuGet package) package file using 7-Zip (a .nupkg file is really just a .zip file). Inside I saw a .nuspec file.

Opening up the .nuspec file reveals its an xml file. After comparing a CTP1 and a 10-26-2010 build version of a .nuspec file I discovered the only difference is an xml namespace reference.

CTP 1 version of a .nuspec file:

<package>
    <metadata>
        ...

10-26-2010 build version of a .nuspec file:

<package xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <metadata xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">

It took a few minutes to update all my .nupkg files to the new format and now everything works again!

Source code for the MonoMac presentation

Dan Morphis — Wed, 28 Jul 2010 06:53:29 GMT

Tonight, I did a presentation on "Developing a .NET application onMac OS X using MonoMac" at the Alaska .NET Users Group meeting. I hope everyone enjoyed my presentation and learned something from it! I'd appreciate any feedback anyone has to offer!

The download link is at the end of this blog post. If you download the source, you will probably want to review all the posts I've written on MonoMac as well.

Source Code

MovieTimes source code

Make a PC keyboard on a Mac function like it should

Dan Morphis — Fri, 09 Jul 2010 02:54:57 GMT

I use and enjoy my Microsoft 4000 keyboard very much. Its the best keyboard I found since the original Microsoft Natural Keyboard. Key placement makes sense, is comfortable to type on, I love the media keys (but honestly, why no love for next and previous track?).

The one thing I don't like however, is how Mac OSX handles PC keyboards. Why does home/end move me to the beginning and end of my document? Everybody knows they are supposed to move the cursor to the beginning and end of the current line. Thankfully, we have Double Command to help fix the issues! If only it could make the page up/down keys function like on the PC...

Whats up with the state of web services in objective-c?

Dan Morphis — Wed, 07 Jul 2010 07:15:56 GMT

After I finished creating a sample application to test out the capabilities of Mono on the Mac, I figured I should create the same application in Objective-C to have an accurate understanding of what the pain points are in each technology.

The first big pain point I've come across is creating the bindings to call a web service in Objective-C. Apple provides a utility called WSMakeStubs. The utility makes creating the stubs easy and painless, or so it would seem. Out of the box the code doesn't compile.

For reasons unknown to me, WSMakeStubs utility makes duplicate method names. The issues people have with WSMakeStubs are so bad, almost every article I've read, everyone advocates using NSUrlConnection and NSXMLParser and rolling your own service calls.

Its 2010 Apple, how about coming up with a viable solution to making web service calls? Even PHP has a good web services proxy generator.

Databinding to an NSTableView with a MonoMac app

Dan Morphis — Mon, 05 Jul 2010 16:00:00 GMT

I’m working on my presentation for the Alaska .NET Users Group. My goal is to build an app that consumes a web service, and displays the data. After getting the web service piece going, the next step was to display that data in a NSTableView.

I battled for hours and hours trying to figure out how to create a NSTableViewDataSource, and it turns out I was making things way to complicated. I did some searching on the web, but couldn’t really find anything except a post by John Moshakis on the Mono-osx mailing list which gave me some hope that someone had figured it out.

I emailed John, and he was gracious enough to send me some source code to work from. It turns out, I what I had wasn’t far off the mark, I just needed a few pointers.

The DataSource Code

using System;
using System.Collections;
using MonoMac.Foundation;
using MonoMac.AppKit;
using MovieTimes.BusinessLogic;
using System.Collections.Generic;
 
[Register("MyItemDataSource")]
public class MyItemDataSource : NSTableViewDataSource
{
    public List<MyItem> MyItems { get; set; }
 
    static MyItemDataSource () {
    }
 
    [Export("numberOfRowsInTableView:")]
    public int numberOfRowsInTableView (NSTableView
aTableView) {
        if (MyItems == null)
            return 0;
        return MyItems.Count;
    }
 
    [Export("tableView:objectValueForTableColumn:row:")]
    public NSObject
objectValueForTableColumn (NSTableView aTableView,
NSTableColumn aTableColumn, int rowIndex) {
        return new NSString(MyItems[rowIndex].Name);
    }
 
    public void Items(List<MyItem> items) {
       
MyItems = items;
    }
}
 
public class MyItemDataSourceDelegate : NSTableViewDelegate {
    public event EventHandler<MyItemChangedEventArgs> MyItemChanged;
 
    public MyItemDataSourceDelegate ():base()  {
    }
 
    public override void SelectionDidChange(NSNotification
notification) {
       
var table = notification.Object as NSTableView;
            
       
var ds = table.DataSource as MyItemDataSource;
            
       
var rowNum = table.SelectedRow;
            
        if (rowNum >= 0 && rowNum < ds.MyItems.Count)
           
OnMyItemChanged(new MyItemChangedEventArgs(ds.MyItems[rowNum]));
    }
        
    protected void OnMyItemChanged(MyItemChangedEventArgs
e) {
        if (MyItemChanged != null)
           
MyItemChanged(this,
e);
    }
}
    
public class MyItemChangedEventArgs : EventArgs {
    public MyItem
MyItem { get; set; }
        
    public MyItemChangedEventArgs(MyItem
i) {
       
MyItem = i;
    }
}

The code is kind of long, and I’ve removed all the normal guard code you would use for the sake of brevity. But lets dissect the code. The first part, lines 8 – 31 is the actual data source. It simply listens for a few messages (numberOfRowsInTableView and objectValueForTableColumn) and allows items to be added to the data source (line 28). The next part, lines 33 – 54 fire off an event when the selected item has changed in the NSTableView instance.

The Window Code

public override void WindowDidLoad () {
    base.WindowDidLoad ();
 
   
var myDel = new MyItemDataSourceDelegate();
   
myDel.ItemChanged += ItemChanged;
 
    this.someTable.Delegate = myDel;
    this.someTable.DataSource = new MyItemDataSource();
}

In the window controller, paste the above code to have code run when you window loads. For WinForms people, public override void WindowDidLoad is the equivilent of protected override void OnLoad().

So what does the window controller code do? First off, we create our delegate (note, delegates in Cocoa are not the same thing as in C#), and wire up to the changed event, then we assign the newly created delegate and a data source to our table.

Any questions, thoughts or feedback? Hit me up in the comments, or follow me on twitter.

Some thoughts on mono and Cocoa

Dan Morphis — Mon, 05 Jul 2010 09:28:36 GMT

For the past week or so, I've been developing a couple of sample apps in Mono with Cocoa on my Mac. In that time, I've struggled quite a bit, and learned quite a bit. One of the biggest things I've learned is things are much harder when you try and mix-in paradimes for which things were not designed.

Take for example NSTableView. Because Objective-C is duck typed, you set Delegate property of your table to this (self in Objective-C) and implement the selectionDidChange method and you will get notified when a row is selected.

Because C# is not duck typed, you have to write a whole lot of ceremony code to get notified when a row is selected. And figuring out that ceremony was a huge battle. I wouldn't have won the war without the help of John Moshakis. Another thing thats not supported is Registering a generic type, or setting a generic .NET type the property of a Cocoa widget.

That means the ceremony code has to be duplicated every time, for every different type of object. I actually tried to make a generic version of my Databinding to an NSTableView blog post, but I was thwarted by an "Invalid IL exception." Hopefully this is just a defect, and not a limitation when dealing with Cocoa.

I would file a defect on this issue with the mono project, but Novell requires you to create an account to add a defect to their bug tracker. I can understand why they want you to do this, but its not a very good way to encourage participation from the community. But I guess it is a particularly good way to discourage drive-by defect reports.