OverrideAndNew.cs

void Main()
{
	var son = new Son();
	BaseClass sonAsBase = new Son();

	Console.WriteLine(son.A());
	Console.WriteLine(son.B());
	Console.WriteLine(son.C());
	Console.WriteLine(son.All());
	Console.WriteLine(sonAsBase.A());
	Console.WriteLine(sonAsBase.B());
	Console.WriteLine(sonAsBase.C());
	Console.WriteLine(sonAsBase.All());
}

class BaseClass{
	public string A() => "Base-A";
	public virtual string B() => "Base-B";
	public string C() => "Base-C";
	public string All() => $"{this.A()}{this.B()}{this.C()}";
}

class Son : BaseClass{
	public string A() => "Son-A";
	public override string B() => "Son-B";
	public new string C() => "Son-C";
}