Cairo.Matrix dll gives an Error Object reference not set to an instance of an object

Question

I am using the Cairo.Matrix dll in my monoandroid application to load the some System.Drawing.Drawing2D.Matix Class Methods it works fine at build time  but at run time the Matrix class from Cairo.Matrix gives an error "System.NullReferenceException: Object reference not set to an instance of an object."
                 when I intialize the Cairo.Matrix Class error is "Exception in loading dicom filelibcairo-2.dll."  

   This below code I am trying.......... 
using System; 
using System.Drawing; 
using Medsynaptic.Common; 
using Medsynaptic.Imaging1.Mathematics; 
using Matrix = Cairo.Matrix;

public class SpatialTransform : ISpatialTransform 
    { 
private Cairo.Matrix _cumulativeTransform; 
        private Cairo.Matrix _transform; 
public PointF ConvertToDestination(PointF sourcePoint) 
        { 
            double x = 0.0, y = 0.0;               
            this.CumulativeTransform.TransformPoint(ref x, ref y);                     
            PointF point = new PointF((float)x, (float)y); 
            return point; 
        } 
 Here it show Null Ref Exception:Object reference not set to an instance of an object
public Cairo.Matrix CumulativeTransform       
        {             
            get 
            {                 
                Calculate(); 
                return _cumulativeTransform; 
            } 
        } 
 protected virtual void Calculate() 
        { 
            if (!this.RecalculationRequired) 
                return; 
              ERROR @ if condition:- Object reference not set to an instance of an object
            if (_cumulativeTransform == null) 
                _cumulativeTransform = new Cairo.Matrix(); 

           // _cumulativeTransform.Reset(); 

            _cumulativeTransform.InitIdentity(); 
} 
} 


  so please help me for this it's very urgent. 
Regards 
Pritish M. Deshmukh