Returns true if your the function to be optimized is differentiable, or false if it is not differentiable or you cannot provide its differential.
The differentiability of the optimized function is determined from the type of your function, as sent to the SetFunction method before invoking this method.
If your function class implements the Derivative or Gradient interface (according to whether your function is uni or multi-dimensional), then your function is differentiable. If it implements only the UniDimensionalSolver or MultiDimensionalSolver interface, then it is not going to be treated as differentiable.
EasySolver Class | WebCab.COM.Math.Optimization Namespace