Compatibility between DirectX 9 and DirectX 10 shaders

I am a beginner to game development and as I am used to programming in C# I decided to go for XNA. I've been playing around with it for a while and now I am learning the basics of HLSL shaders, I have noticed in the MSDN documentation that there have been some syntax changes in HLSL between DirectX 9 and DirectX 10, for example, the Sampler type开发者_开发知识库

Since I am having some troubles with my desktop pc, I am using my laptop which video card only supports DirectX 9.0c. Then I'm gonna have to write my shaders using the DirectX 9 syntax, right? So I am wondering, will my HLSL shaders written using the DirectX 9 syntax work on a system running DirectX 10 (or higher)?

If you develop your Shaders for DirectX 9, then they will almost certainly work on a DirectX 10 Graphics card. You would only have a problem if you were to write them the other way around.