Intellisense for custom code fragments
In M# in many places you can add C# code in the middle of your M# definitions. For example to specify the default value for a property.
Let's say you have the following definition:
In the above example, the default value expression is a constant string, which ultimately will be generated in the target Domain entity code. So you know that its true nature is a C# expression, while in the M# definition file, it's just plain string. It would be often handy to use intellisense for code completion and checking write at this level to ensure your code fragment is valid.