need to convert C# 4.0 code C# 2.0..please help me

Question

Actually i have vb code which i needed to convert to c#.

I have converted vb code to c#.

But the problem is i have used C# 4.0 version .It is not supported by my system.

I need to downgrade it c# 2.0. which i don't know.

i am using a dynamic keyword which is not supported in the lower version.

Can any one help me in this.

I am putting days of effort..

Please help me..