Invokes and Delegates in C#

Can someone explain the syntax in this block of code?

Invoke((MethodInvoker)
    (
        () => 
        {
            checkedListBox1开发者_C百科.Items.RemoveAt(i);
            checkedListBox1.Items.Insert(i, temp);
            checkedListBox1.Update();
        }
    )
);

I'm using a backgroundworker which needs to update parts of the UI so I used this. It works, but I don't know what the empty () and => mean.

() and => is a lambda expression.

Action a = () => { 
    //code here
}

is a delegate of type Action, which executes the code in the block.

Func<string> f = () => {
    //code here
    return "string";
}

is a delegate of type Func<string>, which executes the code in the block and then returns a string.

Func<int, int, string> f = (i, j) => {
    //code here
    return "string"+i+j;
}

is a delegate of type Func<int, int, string>, which has two int parameters referred to i and j in the code block and returns a string.

Etc...

() => introduces a lambda expression.

If the lambda expression received parameters then they would be listed inside the parentheses. Your lambda is equivalent to

void foo()
{
    ...
}

that a Lambda eExpression. The epmty brackets mean that it does not accept any parameters.

Although this snippet seems like it's missing something, don't think it compiles. W

hat Invoke does is call the UI thread. When you do processing, you want to do that on a background thread, and only make short calls to the UI thread. That way you keep the UI responsive.

So this snippts passes a piece of work (add items to the Combobox) to the UI thread to have it done. A background thread cannot directly do things on the UI thread.

Regards GJ