Most advisable way of checking empty strings in C#

Question

What is the best way for checking empty strings (I\'m not asking about initializing!) in C# when considering code performance?(see code bel

Answer 1

string.IsNullOrEmpty(a)

it will check both NULL || EMPTY

this is the Implementation :

public static bool IsNullOrEmpty(string value)
{
    if (value != null)
    {
        return (value.Length == 0);
    }
    return true;
}