Assign ItemsSource to a Responsive Variable

The ObservableCollection class is nice for updating interface collections (such as dropdowns and listboxes) on the fly. Initialize the CList variable publicly. After that you can adjust that variable in any event and see immediate results.

The following example adds items to a combobox.
Now adjust the variable and see the GUI combobox change instantly.

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Named Arguments

This may seem trivial but I just recently came across this gem. Named Arguments allow you to specify which argument a value belongs to in a method call. One of its advantages is that it frees you from looking up the order of parameters in the call. Meh! That may be cool for some but I find myself around knowing that answer from intellisense while typing. But an application that is useful is if you have a slew of optional parameters and you only need to adjust one or more further down the line.

The following is a traditional way in which you would adjust a distant optional parameter. You would have to supply all the argument values that proceed it:

Now using named arguments you can call it as follows:

It simplifies the call and makes it easier to know the meaning of each argument at a glance. There have been times in the past where I have used Overloading to bridge the argument gap. Now with Named Arguments, I have another tool in my arsenal to supply arguments in a precise and intelligible way.

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C# Referencing List Items with Both Indexes and Strings

Defining an indexer allows you to create classes that act like “virtual arrays.” Instances of that class can be accessed using the [] array access operator. Examples include Settings[0] or Settings["ComputerID"]. See the code below:

Another option is an extension method. Call it like Settings.GetByName("ComputerID"):

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Use a Counter with a Foreach Loop in Razor

Using bootstrap I wanted to create a two column grid with the data provided to the model. To accomplish this I needed to surround every two divs of class col-sm-6 with a div of class row. To do this I implemented a counter. I then used modulus to determine if I should open the tag or close it.

Another thing to note is that razor shows syntax errors if you just include an opening tag without its closing tag. If you run the code you will likely get a broken page complaining about missing curly braces. To get around this prepend each tag in their respective if-statements with @:.

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Cancel/Abort a Closing Window in Xamarin.Mac

Close Dialog

I began by researching the WillClose event to accomplish this. With it I could detect the window as it was closing but could not find a way to abort with the EventArgs provided. I achieved success with a delegate class that overrides the WindowShouldClose method .
Put this class in the window.cs below the partial class that was pregenerated:

Assign the delegate wherever you instantiate the window controller:

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Comparing C# Objects

There are times when you need to compare objects. Microsoft includes a built-in Equals function. When it comes to comparing instantiated objects it will return False unless the two objects are the result of the same instantiation. If your definition of equality is the two objects of the same type with the same property values then you need to implement a different approach. I typically serialize the object then compare the string values.

The JsonConvert object is included with the Json.NET nuget.

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Center a Window in Xamarin.Mac

To make my window appear front, centered and focused I have had success with the following:

This works exceptionally well when invoked from a NSStatusBarItem.

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Add Code Behind to a Resource Dictionary

I recently used a Resource Dictionary and wanted to be able to tweak the xaml components on it behind the scenes. This can be accomplished fairly easily:

  1. In your project add a new class file. Give it the same name as the xaml.
  2. In the newly created file override the contents of the namespace with this code:
  3. Next, go to your <ResourceDictionary> tag in the xaml file. Add this property with the appropriate namespace and name: x:Class="namespace.classname"

Now the two should be linked up. In Visual Studio, however, they will not be nested like normal xaml files. This bugged me. I read online that the csproj file can be edited in notepad to accomplish this. I tried and for some reason I couldn’t get it to take. I did have success with VSCommands. It is an install that adds extra features to Visual Studio. Once installed select the xaml and cs with your mouse in the tree. Right-click and choose Group Items. Choose the xaml as the root item to be conventional. Now Solution Explorer should show them as paired.

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Invert the Transparency in an Image with Gimp

You can easily invert the transparent parts of an image with Gimp. Gimp is an open source Photoshop alternative.

Follow these steps:
  1. Choose Colors -> Components -> Decompose from the menu and set Color model to RGBA.
  2. A new image is opened with all color channels (including alpha channel) decomposed as single layers.
  3. Select the layer alpha and choose Colors -> Invert from the menu.
  4. Choose Colors -> Components -> Compose from the menu, set Color model to RGBA and make sure the layers are correctly mapped to the channels (should default correctly if you did not reorder the layers)

It will open a few new Gimp tabs but it will, indeed, invert the transparent areas of the image. This worked well for me on an image of a single color with transparency.

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How to Queue up Method Calls in C#

First you need to instantiate a List of type Action:

Next, we will add methods to the list. We do this through Lambda Expressions using a specific syntax: () => { TestFunc("data") };

With this technique local methods can be stored along with parameters for future execution. In the example below you can see two Console.WriteLine statements. But since the first method is housed in the expression it does not fire until executed later. However, the subsequent one will fire immediately and be listed first in the output tab of Visual Studio:

To fire off each method loop through and use function params to execute:


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