C#

Fresh from Twitter, here are some ways to use attributes in C# that you might not know ...

Did you know you can put attributes on method parameters ...

public string MyMethod([MyCustomAttribute] int id)
{
    // ...
}

Did you know you can specify an attribute on the return of a method ...

[return: CrazyAttributeOnAReturnMethod(WithAParameterOfItsOwn = true)]
public string MyMethod(int id)
{
    // ...
}

For the record: I knew the first, but not the second ...

A lot of the discussion about .NET 4.0 is revolving around the introduction of co-variance and contra-variance for generic types.

It's important to remember, though, that these concepts aren't entirely new - there has been some support for variance built into .NET for some time.

For example, consider this snippet of code:

    public Form1()
    {
        InitializeComponent();
 
        textBox1.KeyPress += Handler;
        button1.Click += Handler;
 
        textBox1.KeyPress += new KeyPressEventHandler(Handler);
        button1.Click += new EventHandler(Handler);