Can a variable begin with a number after an underscore? For example like : _1name

Answer 1

Yes :)

Answer 2

The underscore is simply a convention; nothing more. As such, its use is always somewhat different to each person. Here's how I understand them for the two languages in question:

In C++, an underscore usually indicates a private member variable.

In C#, I usually see it used only when defining the underlying private member variable for a public property. Other private member variables would not have an underscore. This usage has largely gone to the wayside with the advent of automatic properties though.

Before:

private string _name;
public string Name
{
get { return this._name; }
set { this._name = value; }
}

**************************************

After:

public string Name { get; set; }

**************************************

Answer 3

to add to what the above poster said and iterate on the convention aspect of this question it is different for everyone. I typically use underscore when declaring global variables