How to upgrade to .NET 3.5?

Our company uses .NET 2.0 to develop server application which is installed at a number of large customers. We still use 2.0 only because it is installed on all customer servers by default.

For us,开发者_高级运维 as developers, this is sometimes total madness, especially for those who migrated from .NET 3.5. We can't use most powerful language and framework features we got used to. Lack of WCF and LINQ really sucks.

How to convince our clients to migrate to .net 3.5? As I understand, the most important problem here is downloading and installing the monstrous .NET runtime (250M?) which is simply impossible.

Let them know that development time will be decreased that will save them money.

How healthy is your Active Directory? (if any)

If I am not mistaken windows updates will end up installing 3.5 on all machines where it is allowed to run, so you may not have a real problem here.

Why not use the Client-only Framework subset? It allows you to only have the user's computer download the client assemblies for the .NET framework, which is only about 26MB. See here.

If you have all of your clients in .net 2.0 then you can explain them how much beneficial the .net 3.5 will be and security concerns as well .