I love dungarees and there is a dungaree for every occasion!  Casual or denim ones are the most popular but there are a few smarter styles and fabrics that would be great to wear for work, dinner or to a party. 

I recent wore these (from Ark £26) cropped, smarter style ones to an event and loved them.  

Here are a couple more smarter dungaree styles that have caught my eye:

Zara £39.99 / Urban Outfitters £66

I wore a black t-shirt under mine, but a shirt or sleeveless top would also work well - it depends what look you want to go for.  My boots are from Clarks V&A Collaboration (£120).

To breastfeed - lift up underneath t-shirt, wear vest underneath that comes down, then dungaree strap comes down or you get access from the side.