Month: November 2008

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C# 4.0 Gets dynamic

I’ve been watching some of the PDC 2008 videos online.  One of the highlights is The Future of C# by Anders Hejlsberg, and I highly recommend it to anyone that’s interested in .NET.  Most of the session focuses on the dynamic capabilities that are coming to C# 4.0.  The .NET Common Language Runtime (CLR) was built primarily with static typing (aka “strong typing”) in mind, in which every variable must be explicitly declared and assigned a type (string, integer, etc.).  Microsoft recently built the Dynamic Language Runtime (DLR) to support dynamic (non-static) languages, such as Python and Ruby, and they are using the DLR to bring some dynamic features to C#.

To you strong-typing zealots, there’s no need to be alarmed.  C# is not transforming itself from a static to a dynamic language.  There is a gap between static and dynamic languages, and the focus is on closing that gap and improving the interaction.  It just so happens that FoxPro is a dynamic language…

To illustrate the problem, here is a simple VFP class I wrote that finds a customer and creates an object for the customer using Scatter:

Define Class Customers As Session OlePublic

oCustomer = NULL

Procedure GetCustomer(lcCustomerID As String)
Local loCustomer

If !Used("Customers")
 Select 0
 Use (Home(2) + "Northwind\Customers")
Else
 Select Customers
EndIf
Locate For CustomerID = lcCustomerID
Scatter Name This.oCustomer Memo

EndProc

Procedure Destroy

Use In Select("Customers")

Endproc

Enddefine

I compiled the class into a COM DLL and imported it into my C# project.  (For more on that, see Rick Strahl’s article: .NET Interop for VFP Applications.)  Since This.oCustomer is created dynamically at runtime, FoxPro cannot include it in the type library.  Therefore, to access any properties of the oCustomer in C#, you have to use “reflection”.  Here’s the C# code:

string CustomerID = "ALFKI";
netcomtest.Customers oCustomers = new netcomtest.Customers();

oCustomers.GetCustomer(CustomerID);
object oCust = oCustomers.OCUSTOMER;
//use reflection to access object properties
object CompanyName = oCust.GetType().InvokeMember("COMPANYNAME", BindingFlags.GetProperty, null, oCust, null);
object ContactName = oCust.GetType().InvokeMember("CONTACTNAME", BindingFlags.GetProperty, null, oCust, null);
//display company and contact name
MessageBox.Show(CompanyName.ToString() + ContactName.ToString());

What a mess!  If I wanted to access all of the properties on the object, this would get very tedious.  C# 4.0 makes the process easier by introducing a new “dynamic” type.  This tells C# to resolve the type of the variable at runtime (just like Fox would), rather than at compile time.  If I understand Anders correctly, here’s what the new code should look like :

string CustomerID = "ALFKI";
netcomtest.Customers oCustomers = new netcomtest.Customers();

oCustomers.GetCustomer(CustomerID);
//create dynamic reference to object
dynamic oCust = oCustomers.OCUSTOMER;
//display company and contact name
MessageBox.Show(oCust.CompanyName + oCust.ContactName);

Now, isn’t that better?  I can actually understand this code.  I can access all the properties of oCust directly, just like I would in FoxPro.  It’s nice to see that COM Interop is one of the things that Microsoft is still improving.

Anders also showed some things they are working on beyond C# 4.0.  Fast forward to the 60 minute mark in the video to see the cutting-edge stuff they are working on.  In short, they are rewriting the compiler, so they can do stuff like put code into a string variable and evaluate/execute it at runtime.  Fantastic!  Anders took it a step further and showed C# commands being executed as he entered them into a window.  Unbelievable!  It’s amazing what they can do these days!  Seriously, should you find yourself working with C# in the future, it will be nice to have some capabilities we’ve grown to love in VFP.

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Grid Header Checkbox

Here’s a little goodie for readers of my blog.  I have several grids that contain a checkbox column to select items in the grid.  I wanted an easy, consistent way to select/deselect all checkboxes in the column, so I created a custom grid header class to do that.  hdrCheckBox.zip is attached (Download).

I initially tried to use a standard checkbox.  VFP doesn’t let you put a control inside a header, so I tried to overlay it on the grid.  That turned out to be too flaky and limited, so I opted to use pictures of a checked and unchecked box, which VFP does do.  The only downside is that the checkbox is a themed control, and Windows XP checkboxes may look slightly different than pictures of the Windows Vista checkboxes I used.  Still, I think the checkbox will look good in any theme.

Another limitation is that the header cannot receive focus like a real checkbox, so no keyboard support.  To get around that, the header Click() is performed when the user presses “A” while the grid column has focus.  I actually tried to use Ctrl+A, but KeyPress() would not detect that combination, I assume because it’s already assigned to the Edit menu.

To make sure the user would know that they could check the box, I put a tooltip on the grid header.  Header tooltips don’t work in VFP9 SP2, so I had to put some workaround code in the class to make the grid tooltip appear.  Hopefully, Microsoft will eventually release a fix for this, but I’m not holding my breath.

To use the class:

  • Change the column HeaderClass to hdrCheckBox in hdrCheckBox.prg.  You may already be done.
  • If you want the box to be checked initially, change the Value property to .T.  Even though this is a PRG-based class, you can use the property sheet and override methods on the form just like you would with any class.  NOTE: Setting this initial value will not check all the boxes in the grid.  You will need to do that in the Grid.RecordSource query.
  • If you want to change the header checkbox back to its original value (for example, if you requery the grid), then call the Reset() method on the class.
  • Another VFP9 SP2 bug!  If you open this form from the menu, you have to use the menu “Procedure” to open the form instead of “Command”.  Otherwise, VFP9 will crash when you open the form.  See Emerson Reed’s blog entry for more info.

Here are the requirements to use the class (which, of course, you could change):

  • Grid.RecordSource is required.
  • Column.ControlSource is required.
  • The column field must be a logical field.
  • Column.CurrentControl must be a checkbox.

Disclaimer: This code is provided AS-IS.  If it doesn’t work for you, fix it!

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Head in the Cloud

With Microsoft’s unveiling of Windows Azure at the PDC last week, I’ve been trying to get my head around exactly what Azure is, or more specifically, why this “cloud computing” thing is so important to Microsoft. What is cloud computing? Heck, what is the “cloud”? According to Wikipedia:

The cloud is a metaphor for the Internet (based on how it is depicted in computer network diagrams) and is an abstraction for the complex infrastructure it conceals.

Ok, so the cloud is the Internet. Why not just call it the Internet? Evidently, it’s a more abstract, architectural way of looking at the Internet that’s not concerned with all the hardware and network protocols under the hood. You connect a router to the “Internet”. You put a service in the “cloud”. Indeed, when talking about cloud computing, people often refer to delivering “software as a service” or “software + services”. It’s broader than that and actually has been around for a while, so what’s the big deal? “Cloud computing” is a buzz-word, to be sure; a repackaging of existing concepts and sold as something new. In this case, the packaging could provide some benefits.

So, what is Windows Azure then? First of all, let’s state the obvious: this is web hosting from Microsoft. When it comes to hosting, you have a couple of options: inexpensive shared hosting, which is fine for static web sites and sites that need little processing power, and dedicated hosting, where you get your own machine(s) for mission-critical stuff. Azure Services is kind of a hybrid approach, where you pay for dedicated resources on Microsoft’s data center, but it’s all virtualized and you don’t know about the hardware underneath. Windows Azure is the base platform for managing all of that, an operating system of sorts with APIs exposed to developers.

My first thought is that this would be something Microsoft could sell to ISPs, but once I realized the scale of what they are trying to do, you really do want a Microsoft, a Google, or an IBM behind it. Scalability and reliability are the name of the game. When you sign up, you get an instance on the data center, which is presumably a virtual machine running Windows Server, but I don’t know the exact details and there’s probably more to it than that. You can have as many instances as you want (or can afford) on-demand, and you pay for exactly what you use and for how long you use it. Microsoft demonstrated scaling instances up or down by simply changing a setting in a config file.

How could that be useful? Imagine you’re offering a new web application and you need to easily scale up as you grow. Or maybe you’re an online retailer and you need to quadruple your web capacity during the holiday season. To get more granular, maybe you need 10 servers running your web site during peak hours but only 2 in the middle of the night. That’s the pitch, anyway.  Whether or not anyone actually needs that much flexibility remains to be seen, but it could be enough to convince some people to buy in.

So, how much is this gonna cost? Good question. Microsoft hasn’t released pricing yet, but they are going to have to be competitive with Amazon’s “Elastic Compute Cloud“. I looked at their pricing, and since everything is a-la-carte down to the hour and the gigabyte, I still don’t know. As far as I can tell, a single instance running 24/7 costs about $150-$200/month. That’s comparable to dedicated hosting, but if you added on the managed features you get with EC2 (backups, etc.) to dedicated hosting, EC2 may actually be cheaper than dedicated (I’m sure people will be analyzing and debating that for some time).  Of course, Microsoft has services such as .NET Services and SQL Services that sit on top of Windows Azure, as well as full-blown applications like Office and CRM, so it’s really going to depend on what you need. I hope Microsoft makes it easier than Amazon to determine your costs.

With this highly scalable and supposedly reliable system, will businesses move their applications to the cloud? I think you’ll see some of that, but the basic rules for determining if an application is a good candidate for the web haven’t changed. If a company relies on their line-of-business software for daily operations, I doubt they’ll risk being shut down because their DSL or T1 line goes down. However, maybe the cloud is the ideal place for their CRM system. Microsoft realizes that businesses are not going to put everything in the cloud, so part of .NET Services is to help companies bridge the gap between their on-premises and cloud systems. For example, logging in to your local network can also log you in to the CRM app in the cloud.

Now, for the million dollar question: Can you run FoxPro applications on Azure? Maybe, but not yet. Azure will initially be for managed .NET code only, but Microsoft claims they will open it up to unmanaged code in 2009. We’ll have to wait and see if that includes VFP.

Resources:

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FoxTabs Reloaded

Rewind to 2004 when VFP 9.0 was in beta. Microsoft added the ability to bind to windows events from FoxPro. The first thing that came to my mind was the ability to hook into VFP IDE windows. I like to work with my code windows maximized and with several windows open at the same time. Constantly going to the VFP window menu to switch windows got tedious. If I could create something like the windows task bar for the VFP ide, that would make life easier and probably be valuable to other people as well. So, I started to ask around about how this could be accomplished. Calvin Hsia put together a sample that he showed at his advisor DevCon (2004?) session. It is now part of the VFP 9 solution samples. I used that as the basis for my utility, and “FoxTaskbar” was born.

I learned a lot about windows events and the FoxPro window system, but I also learned how to crash VFP frequently. Alas, I couldn’t get FoxTaskbar to function stably. After several attempts, I eventually retreated from binding to windows events and tried to use fox’s standard windowing system. I couldn’t get that to work well either, so FoxTaskbar never saw the light of day.

Fortunately, Scott Scovell and Craig Bailey were working on an almost identical tool called “FoxTabs”. Even the internal architecture was similar to FoxTaskbar. I guess great minds think alike <g>, but greater minds actually make it work, and that’s what Scott and Craig did. FoxTabs does exactly what I wanted with FoxTaskbar, and as a bonus, it doesn’t crash VFP every 30 seconds <g>.

In the meantime, Craig and Scott have moved on to other things (Craig is currently looking for his next big adventure), so FoxTabs hasn’t been in development for a couple of years. I had some issues with it, so I recently contacted Craig to see if FoxTabs was still in development. Neither Craig nor Scott has time to continue working on it, so they graciously offered to turn the project over to VFPX. I volunteered to be the project manager, and FoxTabs is now in development again.

FoxTabs 0.5 is now available on the VFPX web site. Please download and start using this handy little utility and help us get to a 1.0 release. I’ve already received bug reports from several developers (that’s a good thing <g>) and progress is being made. Please report any bugs you find on the VFPX issue tracker, and be sure to include “FoxTabs” in the title.

 

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Diving In…

After the excitement of the Southwest Fox conference, I decided to get more involved in VFP community efforts and start a blog. Confession… That was how I felt after SW Fox 2007. A year and another excellent SW Fox conference later, I’m finally getting around to doing it. So, here it is. The content will be mostly fox related, forward looking, and hopefully relevant to you. If I have my way, it will be updated on a regular basis. Enjoy!