Question

it’s possible?

based in another’s examples, as LabelExtesios, StringExtensions, etc.
I wrote this:

namespace MessageBoxExtensions
{

    public static class MessageBoxExtensionsClass
    {
        public static void Foo()
        {

        }
    }
}

then:

using MessageBoxExtensions;
// ... 

MessageBox.Foo();

gin an error: MessageBox.Foo();

'System.Windows.Forms.MessageBox' does not contain a definition for 'Foo'

Answer 1

Description

You cant do this because System.Windows.Forms.MessageBox is NOT an instance of MessageBox. MessageBox.Show() is a static method.

You cant create an instance of MessageBox because this class has no public constructor.

Update

But you can create your own class in the System.Windows.Forms namespace and use the
MessageBox in this method like this

Sample

namespace System.Windows.Forms
{
    public static class MyCustomMessageBox
    {
        public static void Foo()
        {
            MessageBox.Show("MyText");
        }
    }
}

MyCustomMessageBox.Foo();