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Posts Tagged ‘tool’

Silverlight 4 introduces XPath support including XPathNavigator and LINQ to XML extension methods for evaluating XPath expressions on your XElement objects! For those that aren’t familiar with XPath, it is essentially a big string that contains specially formatted text that is interpreted at runtime to describe a pattern for finding nodes in an XML document. You can use it to find nodes with specific conditions much like how regular expressions finds smaller strings in a bigger string. 

The downsides to using XPaths are 1) the string describing your XPath can get quite complicated and difficult to read, and 2) because the string must be interpreted at runtime, performance is worse than alternate methods. This is why I normally discourage using XPaths and probably why Microsoft shyed away from including XPath in earlier versions of Silverlight… thereby bolstering using the better practice of LINQ to XML for searching and parsing XML documents. However, XPaths (like regular expressions) have their place and at times come in very handy! 

One particular use that I’ve come to love over the years is the ability to create and run XPath queries at runtime. You don’t have to know very much about XPaths to easily write simple ones like “/vehicles/car” to find all the ‘car’ nodes in the ‘vehicles’ node. Or slightly more complex XPaths like: “/vehicles/car[@color=’green’]” (find all car nodes with a ‘color’ attribute of ‘green’). Because an XPath is just a string, it is very easy to assemble at runtime or even allow a power users to enter it in the UI if you dare open that can of worms 🙂 However, there is one kind of user I feel perfectly comfortable allowing in the can of worms… developers. Which is why I’ve created… 

XPathPad

How often do you just want to find out very simple information about an Xml file? Maybe you want to know how many nodes are in your document or how many have a certain attribute. Maybe you want to extract the text values from certain nodes so you can use them in another application. Maybe you want to paste all the values of a certain attribute into Excel so you can manually graph them. The possibilities are endless and if you ever have to work with Xml files (especially someone else’s), a tool to easily help without writing a program can be invaluable! 

How to use it:

  1. Run the app. Note: You can also install Out of browser.
  2. Browse for any xml file…
  3. Type in an XPath for the nodes you want to find
  4. Type in another XPath in the Output field for what stuff in each of those nodes you want to display.
  5. Click Go

 

Note: You can optionally enter a comma delimited list of XPaths in the output field if you want to get multiple things about each node found. Multiple results per node are separated by tabs so you can easily copy and paste the results into Excel and get different columns for each.

How it works under the hood:

Silverlight 4’s new XPath features did just about all of the work for me. First, I had to add a reference to the new XPath assembly:

Then, I simply load a standard XDocument from a filestream and call the new extension method that is available:

IEnumerable<XElement> elements = xdoc.XPathSelectElements(XPath);

This returns all the elements found at the provided XPath. I then loop thru each of these elements and call a second extension method to get a node relative to that element based on the output XPath:

var result = element.XPathEvaluate(outputXPath) as IEnumerable;

XObject value = result.Cast<XObject>().FirstOrDefault();

if (value is XElement)

    return ((XElement)value).Value;

else if (value is XText || value is XCData)

    return ((XText)value).Value;

else if (value is XAttribute)

    return ((XAttribute)value).Value;

else

    return value.ToString();

XPathEvaluate returns a collection of XObjects. I simply take the first one and return its value to be displayed in the results window.

To find out more about how XPathPad was written or to modify it to better fit your needs, download the source.

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Here’s a new panel to add to your tool chest. It’s one I expect to use almost daily and save approximately 3.1 hours of typing over the next year. Hopefully you’ll find it useful as useful as I think it is.

What’s wrong with the built-in StackPanel:

You can’t get children to conform to the size of the panel. Imagine you want the following label and list but want the height of the Listbox to stretch or shrink according to the room available:

At first glance, a StackPanel would seem to be the natural choice for which panel to accomplish this. Afterall, you just want a linear list of two objects: a TextBlock and ListBox. However, unless you are willing to hardcode the size of the ListBox or resize it with code, with a StackPanel you’ll end up with:

Yuck! Clipping instead of a scrollbar. So how do you get the desired behavior?

Answer: Grid.

So what’s wrong with a Grid?

  1. Grids take more lines xaml to create. Compare the StackPanel Xaml to the Grid’s above and notice the 4 extra lines of Xaml. Ok, not a huge deal but if you’re doing this every day like me, you start to get sick of creating RowDefinition and ColumnDefinition objects.
  2. With a grid you have to explicitly define the order of the children. Adding the attached property Grid.Row is easy on your first pass but what happens if you want to insert a new row somewhere in the middle. You not only have to add a new RowDefinition, but you also have to remember to go increment the row number on all subsequent siblings. This is a pain and error prone because a sibling would potentially be defined in any order in the grid.

Wouldn’t it be great if you could get the best of both worlds?

What we really want here is a StackPanel that allows you to define the size of the children.

Welcome SuperStackPanel:

Just set the attached property StackPanel.Length to “*” to get a child to stretch.

In fact, SuperStackPanel lets you use all the same GridLength values you can use in a Grid (Auto, *, n*, and x):

Have I sold you yet? The nice part is that SuperStackPanel is completely compatible with a normal StackPanel. Just swap out your StackPanel for SuperStackPanel and everything will look the same because the default value of Length is “Auto”. Frankly, I’d love to see Microsoft expand the role of StackPanel to support this natively. Of course, until then, there’s SuperStackPanel.

SuperStackPanel is lightweight and simple to add to your project, just download the C# source code, add to your project, add the namespace to your xaml and away you’ll go. Enjoy!

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ASP.NET allows you to get at some great information about the client and the server via the HttpContext.Current.Request.ServerVariables collection. Likewise, Silverlight allows you to get at a few local variables of its own through the System.Windows.Browser.HtmlPage.BrowserInformation object.

But, to use these variables we often need to know what kind of values to expect. For example, let’s say you’re going to create a condition based on which browser the user is using. You would use BrowserInformation.Name. But Name is a string, not an enum. So what are the various values that can be returned by this property? This might be documented somewhere for the officialy supported browsers, but the only fool proof way is to actually try it by writing a dummy Silverlight app that spills out this variable and run it in all the different browsers to see what comes back. The same applies to ServerVariables but even more so because this is just a big dictionary so you don’t even know which variables are going to be present let alone what their values will be.

Here’s a utility I wrote for anyone to use that will help you look at all the BrowserInfo properties and ServerVariables. Hit this page from any machine to see what values it is sending up to the server. Bookmark this page, it will probalby come in handy someday when you’re scratching your head wondering what useragent you’re sending up to the server.


BrowserInfo and ServerVariables

Another cool part is that it not only shows you what servervariables are available at the time your web page is requested, but also what servervariables are available when you hit a WCF service from Silverlight. There are some subtle differences.

Also note that it’s hosted on Azure so you can also get a glimpse of which ServerVariables Azure provides access to. On first glance it looks the same as Windows Server but I haven’t done a variable by variable comparison.

Enjoy, I hope this comes in handy!

Download the source code here to see how it works or to host on your own server.

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I always try to use named colors whenever I can because it makes your Xaml much easier to read! Who knows what color #1A37C5 is? Okay, so maybe some of you can “see into the matrix” but I’d much rather see something like “DarkBlue”. It’s also easier to write because you VS gives you IntelliType when entering a color for a property of type Brush or Color.

Here’s a super easy way to see all the named colors out there that Silverlight supports. This tool also supports copying the name by selecting it and using Ctrl+C. Plus, you can sort the list alphabetically, by red, blue, green, hue, saturation, or luminosity for those of us that get dizzy scanning the palette for a good “blue” to choose.

namedcolorsviewer
Click to Run

Note: Microsoft has a pretty good table of their own with all the same colors in my tool (there are 141 of them by the way, not 240 as stated on the MS site). But the colors blocks are smaller, it’s all just a big image so you can’t copy names, and it of course lacks my patented sort feature 😉

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Need a way to duplicate a chunk of text for each variable in a list? This tool will save you time and soar wrists by letting you create a template and a list of variables and merge the two to get a repeated chunk of text with variables injected into each iteration.



Click To Run

For example, let’s say you had a list of 100 names of colors and you wanted to generate a function in code for each. Supply the list of colors as your “variables” and set your “template” to:

function #value#() { }

And let the TemplateRepeater take it away generating a chunk of text for each color resembling:

function blue() { }

function red() { }

function green() { }

Simple but surprisingly useful! Enjoy!

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