You should define the following function f(i,j,k) which gives you the maximum value you can get by selecting exactly k items from the first i items (1,2..i) with maximum capacity of j.
according to our definition the transitions will be:
f(i , j , k) = max( t1 , t2 ) t1 = f(i-i , j , k) // here we did not pick the i-th item t2 = vi + f(i-1 , j - ci , k-1)// here we picked the i-th item
the result to your question will be max( f(n,C,i) ) where i=1,2…n
CLICK HERE to find out more related problems solutions.