Hi,
I am using the Eigen and UMFPACK in viusal studio 2010, but it says

error C2039 "data" is not a member of Eigen::CwiseBinaryOp<BinaryOp,LhsType,RhsType>

at this line

eigen_assert(b.derived().data() != x.derived().data() && " Umfpack does not support inplace solve"); in the file "UmfPackSupport.h"

whis is the matter

You are probably calling compute() or solve() with an expression and not a matrix. This should be fixed in the devel branch. You can workaround by calling .eval() on the expression, like lu.solve((a+b).solve()) instead of lu.solve(a+b).