The original string if not null or empty, otherwise the replacement string.
#### Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type <ahref="https://learn.microsoft.com/dotnet/api/system.string"target="_blank"rel="noopener noreferrer">String</a>. When you use instance method syntax to call this method, omit the first parameter. For more information, see <ahref="https://docs.microsoft.com/dotnet/visual-basic/programming-guide/language-features/procedures/extension-methods"target="_blank"rel="noopener noreferrer">
Extension Methods (Visual Basic)</a> or <ahref="https://docs.microsoft.com/dotnet/csharp/programming-guide/classes-and-structs/extension-methods"target="_blank"rel="noopener noreferrer">