Difference between using delegate and non-delegate method as argument in Contol.Invoke to avoid cros-CodePudding

I try to use a separate thread modifing visual control. I know how to use delegate to avoid a cross thread exception like this.

delegate void LabelTextDelegate(string _String);

LabelTextDelegate LabelTextDelegate1;

private void Form1_Click(object sender, EventArgs e)
{
    LabelTextDelegate1 = new(LabelText);

    new Thread(Method1).Start();
}

void Method1()
{
    label1.Invoke(LabelTextDelegate1, "a"); // delegate
}

void LabelText(string _String)
{
    label1.Text = _String;
}

But the following code simpler works well too.

private void Form1_Click(object sender, EventArgs e)
{
    new Thread(Method1).Start();
}

void Method1()
{
    label1.Invoke(LabelText, "a"); // non-delegate method
}

void LabelText(string _String)
{
    label1.Text = _String;
}

What is the difference? Is the latter correct? If so, I know Control.Invoke needs a delegate as an argument and does it change non-delegate method to delegate internally?

CodePudding user response：

Your "non-delegate method" is still using a delegate. It's using a method group conversion to a delegate type (in this case to Action<string>).

Your code is equivalent to:

void Method1()
{
    label1.Invoke(new Action<string>(LabelText), "a");
}

In earlier versions of C#, the method group conversion wouldn't have succeeded as Delegate isn't a specific delegate type, but as of C# 10, a method group with exactly one overload has a "natural type".

CodePudding user response：

No difference, just the second example use the syntax from C# 2.

To instantiate a delegate :

LabelTextDelegate myDelegate = new LabelTextDelegate(LabelText);

// C# 2 provides a sugar syntax to instantiate a delegate.
LabelTextDelegate myDelegate = LabelText;

It's the same when you pass a delegate as method's parameter :

void Method1(LabelTextDelegate labelText)
{
    labelText.Invoke("a");
}


Method1(new LabelTextDelegate(LabelText));

// With the C# 2 sugar syntax
Method1(LabelText);

More information in the documentation : How to declare, instantiate, and use a Delegate