Using lambda expressions for event handlers
C#PerformanceEventsLambdaC# Problem Overview
I currently have a page which is declared as follows:
public partial class MyPage : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
//snip
MyButton.Click += (o, i) =>
{
//snip
}
}
}
I've only recently moved to .NET 3.5 from 1.1, so I'm used to writing event handlers outside of the Page_Load. My question is; are there any performance drawbacks or pitfalls I should watch out for when using the lambda method for this? I prefer it, as it's certainly more concise, but I do not want to sacrifice performance to use it. Thanks.
C# Solutions
Solution 1 - C#
There are no performance implications since the compiler will translate your lambda expression into an equivalent delegate. Lambda expressions are nothing more than a language feature that the compiler translates into the exact same code that you are used to working with.
The compiler will convert the code you have to something like this:
public partial class MyPage : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
//snip
MyButton.Click += new EventHandler(delegate (Object o, EventArgs a)
{
//snip
});
}
}
Solution 2 - C#
Performance-wise it's the same as a named method. The big problem is when you do the following:
MyButton.Click -= (o, i) =>
{
//snip
}
It will probably try to remove a different lambda, leaving the original one there. So the lesson is that it's fine unless you also want to be able to remove the handler.
Solution 3 - C#
EventHandler handler = (s, e) => MessageBox.Show("Woho");
button.Click += handler;
button.Click -= handler;
Solution 4 - C#
No performance implications that I'm aware of or have ever run into, as far as I know its just "syntactic sugar" and compiles down to the same thing as using delegate syntax, etc.