lambda expression and event handler?

Question

Someone mentioned to me that c# supports to use lambda expression as event handler, can anyone share with me some reference on this?

A code snippet is preferred.

score 13 · Accepted Answer · answered Oct 09 '12 at 00:09

13

You can use a lambda expression to build an anonymous method, which can be attached to an event.

For example, if you make a Windows Form with a Button and a Label, you could add, in the constructor (after InitializeComponent()):

 this.button1.Click += (o,e) =>
     {
        this.label1.Text = "You clicked the button!";
     };

This will cause the label to change as the button is clicked.

answered Oct 09 '12 at 00:09

Reed Copsey

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Yup. I also wanted to point this out regarding adding and removing anonymous event handlers: http://stackoverflow.com/questions/2051357/c-sharp-adding-and-removing-anonymous-event-handler – devshorts Oct 09 '12 at 00:11
@devshorts Yes. It's not necessarily great if you need to unsubscribe as well. – Reed Copsey Oct 09 '12 at 00:13
Aren't the braces redundant for single-statement method bodies? – Superbest Oct 09 '12 at 00:52
@Superbest They're not necessary for single statement bodies - they don't hurt anything, though, and it makes it a bit more clear when reading in a post like this, which is why I wrote it that way. – Reed Copsey Oct 09 '12 at 01:20

score 0 · Answer 2 · edited Jul 21 '19 at 06:48

try this example

public Form1()
{
    InitializeComponent();
    this.button1.Click += new EventHandler(button1_Click);
}

void button1_Click(object sender, EventArgs e)
{
}

The above event handler can be rewritten using this lambda expression

public Form1()
{
    InitializeComponent();
    this.button1.Click += (object sender, EventArgs e) = >
    {
        MessageBox.Show(“Button clicked!”);
    };
}

lambda expression and event handler?

2 Answers2

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