After using Ruby for some time I have become quiet attached to its conditional statement syntax. In particular I like statement modifiers which allow you to tag conditional statements at the end of a normal statement.

If C# supported this then in C# terms this'd mean instead of writing

if (!File.Exist(fileName)) throw new FileNotExistException(fileName));

You could have written

throw new FileNotExistException(fileName)) if (!File.Exist(fileName));

If things go as it seems this could actually be the future of C#.  I know this does not look that intuitive at first, but once I got used to it I started using it at all places. A quick glance in my Ruby sources reveals code like

Utility.showHelp if ARGV.length < 2
ARGV.each do |srcFileName|
    next if srcFileName =~ /^-/ #skip arguments starting with a -
    ...
end

I liked the unless keyword as well. This is a negated version of if used in Ruby. If C# supported this then we could have written

unless (File.Exist(fileName)) throw new FileNotExistException(fileName)); 

or better still

throw new FileNotExistException(fileName) unless (File.Exist(fileName)); 

What I felt was not that intuitive is that in Ruby if is not a statment but is an expression similar to the ?: conditional expression in C/C++/C#. So for conditional assignment of values in Ruby you can write code as in

ageGroup = if age < 2
             "Infant"
           elsif age < 19
             "Teen"
           elsif age < 30
             "Middle aged"
           else
             "old"
           end 

In C# this'd become

string ageGroup; 
if (age < 2)
    ageGroup = "Infant"; 
else if (age < 19) 
    ageGroup = "Teen"; 
else if (age < 30) 
    ageGroup = "Middle aged"; 
else 
    ageGroup = "old";