I want to write a program in WPF but not sure should I target .net35 or .net30. The advantages of .net35 are obvious. But still, I see one major advantage of .net30 -- it's built into Vista, so, the people using Windows Vista will not have to download and install the framework.
Do you think the advantages of .net35 outweigh the hassle of downloading ~200 megas and installing in?
P.S.
Actually, I don't need advanced stuff like linq, etc. So, I guess .net30 will suffice. Or am I missing anything?
You can use a number of 3.5 features, such as extention methods if you use the 3.5 compiler. But targeting the 3.0 is not going to hurt you much if the 200mb download is a serious concern
You're right: there is definitely an advantage in not requiring that users download another framework.
A couple of tips: if you're going to target FW3.0, you can still use Studio 2008 rather than Studio 2005 - and the C# 3.0 or VB 9.0 compilers. Simply set the target Framework to 3.0 in project properties. Also, you can still use LINQ to Objects with LINQBridge.
If you're accessing a database, you will miss out on LINQ to SQL (or Entity Framework), which I've found really simplifies development of the middle tier. For me, that would be a reason to favour Framework 3.5.
What you need is .NET Framework 3.5 SP1 Client Profile, which gives you 3.5 with minimal installation size, which is usually 2x MB.
I think that's a question only you can answer. Does having the user download/install another 200 megabytes out way your preparation for the future? Although you say that you do not need the advanced stuff, you never know if you're going to need it in the future.
Obviously you could always start in 3.0, and when you really need 3.5, upgrade your project to the newer version (by that time that could also be version 4.0 ofcourse).
来源：https://stackoverflow.com/questions/810693/net-3-5-vs-net-3-0