It looks as if the Visual Studio dev team may be implementing a new operator in a future .NET release. This is due in large part to community demand, which is pretty cool because it shows that the VS team is listening to their customer base; a key part of a successful product.
This new operator is likely going to take the syntax of ?. and is known as the Safe Navigation Operator.
I recently came across an ASP.NET MVC issue at work where the validation for my Model was not firing correctly. The Model implemented the IValidatableObject interface and thus the Validate method which did some specific logic to ensure the state of the Model (the ModelState). This Model also had some DataAnnotation attributes on it to validate basic input.
Long story short, the issue I encountered was that when ModelState.IsValid == false due to failure of the DataAnnotation validation, the IValidatableObject.Validate method is not fired, even though I needed it to be. This problem arose due to a rare situation in which ModeState.IsValid was initially false but was later set to true in the Controller’s Action Method by some logic that removed errors from the ModelState.
Jonathan Allen of InfoQ conducted an interview with me about one of my open source initiatives, SimplSockets. We discussed the value of TCP over HTTP and why Sockets are still relevant to programming.
I’d like to thank Jonathan and InfoQ for the opportunity – it was a great discussion. Check it out here: http://www.infoq.com/news/2013/12/SimplSockets
MVC4 made one simple and yet awesome improvement to View rendering that I don’t think many people are aware of.
Have you ever had to conditionally add an attribute to an HTML element in your MVC View based on the presence of a variable? The typical use case is applying a CSS class to a div. Most of the time that code looks something like this:
<div @(myClass == null ? "" : "class=\"" + myClass + "\"")></div>
What a pain – not only to write but to read… This destroys the View’s readability and clutters the HTML up big time!
If you’re using the Web API as part of the MVC4 framework, you may encounter a scenario in which you must map parameters of strange names to variables for which characters of the name would be illegal. That wasn’t very clear, so let’s do this by example. Consider part of the Facebook API:
Firstly, Facebook servers will make a single HTTP GET to your callback URL when you try to add or modify a subscription. A query string will be appended to your callback URL with the following parameters:
Have you ever had to write a comparer for a specific type, only to be frustrated when you needed to write a second and third comparer for other types? Fear not, a generic comparer can take care of this for you!
/// <summary>
/// Compares two objects of any type.
/// </summary>
/// <typeparam name="T">The type to be compared.</typeparam>
public class GenericComparer<T> : IComparer<T>
{
// The compare method
private readonly Func<T, T, int> _compareMethod = null;
/// <summary>
/// The constructor.
/// </summary>
/// <param name="compareMethod">The compare method.</param>
public GenericComparer(Func<T, T, int> compareMethod)
{
// Sanitize
if (compareMethod == null)
{
throw new ArgumentNullException("compareMethod");
}
_compareMethod = compareMethod;
}
/// <summary>
/// Compares two objects.
/// </summary>
/// <param name="x">The first object.</param>
/// <param name="y">The second object.</param>
/// <returns>Less than 0 if x is less than y, greater than
/// 0 if x is greater than y, 0 if they are equal.</returns>
public int Compare(T x, T y)
{
return _compareMethod(x, y);
}
}
Just pass a method to the constructor that takes 2 objects of type T and returns an int, and you’re all set!
I wanted to point people to this link at DotNetPearls:
http://www.dotnetperls.com/binarysearch
They do an excellent, quick demonstration of List<T>.BinarySearch and show a graph that really drives home how much faster it is for large lists than a regular traversal!
In the interest of self-improvement and sharing knowledge, I felt that I should share an update to my last post. I discovered a slightly better way to create the GetMimeMapping delegate/method via reflection that involves less casting and overhead, and is more Object Oriented in a sense. It allows the signature of the reflected method to be Func<string, string> instead of MethodInfo. Code below, note the use of Delegate.CreateDelegate(Type, MethodInfo):
/// <summary>
/// Exposes the Mime Mapping method that Microsoft hid from us.
/// </summary>
public static class MimeMappingStealer
{
// The get mime mapping method
private static readonly Func<string, string> _getMimeMappingMethod = null;
/// <summary>
/// Static constructor sets up reflection.
/// </summary>
static MimeMappingStealer()
{
// Load hidden mime mapping class and method from System.Web
var assembly = Assembly.GetAssembly(typeof(HttpApplication));
Type mimeMappingType = assembly.GetType("System.Web.MimeMapping");
_getMimeMappingMethod =
(Func<string, string>)Delegate.CreateDelegate(typeof(Func<string, string>),
mimeMappingType.GetMethod("GetMimeMapping",
BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public |
BindingFlags.NonPublic | BindingFlags.FlattenHierarchy));
}
/// <summary>
/// Exposes the hidden Mime mapping method.
/// </summary>
/// <param name="fileName">The file name.</param>
/// <returns>The mime mapping.</returns>
public static string GetMimeMapping(string fileName)
{
return _getMimeMappingMethod(fileName);
}
}