public static ClassDeclarationSyntax AddOrUpdateMethod(this ClassDeclarationSyntax classDeclaration, Func <MethodDeclarationSyntax, bool> predicate,
MethodDeclarationSyntax method)
{
classDeclaration = classDeclaration.AddOrUpdateNode(
classDeclaration.Members.OfType <MethodDeclarationSyntax>().FirstOrDefault(predicate).ToOption(), method);
return(classDeclaration);
}