Best "Visual Studio" Alternative On Linux

Microsoft ISV writes: "We are beginning the next major release of our product, and we have been a Microsoft ISV for many years. In a few months Microsoft will be entering our market, and we wish to hedge our bets by supporting Linux in this next new major release. Can you ask your readership what is the best 'Visual Studio' like IDE for Linux? Especially for an ISV who will be maintaining the same product on both Windows and Linux?" Or is there even such a thing?