C # object removed strangely

this code runs after the button is pressed.

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using xnaWindow.FormUI;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace xnaWindow.MathClass
{    
    public class Math_Vector 
    {
        private Vector3 vectorA;
        private Vector3 vectorB;
        private Vector3 vectorR;
        private List<float> vResult;

        VertexPositionColor[] verts1,verts2,verts3;

        public void calculate(List<float>v1,List<float>v2)
        {
            Console.WriteLine("calculating..");

            vResult = new List<float>(); 
            vectorA = new Vector3(v1.ElementAt(0), v1.ElementAt(1), v1.ElementAt(2));  
            vectorB = new Vector3(v2.ElementAt(0), v2.ElementAt(1), v2.ElementAt(2)); 

            //this is the manual calculation of vector addition
            float xRes = v1.ElementAt(0) + v2.ElementAt(0);
            float yRes = v1.ElementAt(1) + v2.ElementAt(1);
            float zRes = v1.ElementAt(2) + v2.ElementAt(2);

            vectorR = new Vector3(xRes,yRes,zRes);
            //vectorR = vectorA + vectorB; 

            verts1    = new VertexPositionColor[2];
            verts1[0] = new VertexPositionColor(new Vector3(0, 0, 0), Color.Black);
            verts1[1] = new VertexPositionColor(vectorA, Color.Black);

            verts2    = new VertexPositionColor[2];
            verts2[0] = new VertexPositionColor(new Vector3(0, 0, 0), Color.Black);
            verts2[1] = new VertexPositionColor(vectorB, Color.Black);

            verts3    = new VertexPositionColor[2];
            verts3[0] = new VertexPositionColor(new Vector3(0, 0, 0), Color.Black);
            verts3[1] = new VertexPositionColor(vectorR, Color.Black);

            int i = 0;
            //this is for console debug
            foreach (float va in v1)
            {
                Console.WriteLine("adding " + va.ToString() + v2.ElementAt(i).ToString());
                vResult.Add(va+v2.ElementAt(i));
                i++;
            }

        }

        public Vector3 getV1(){return vectorA;}
        public Vector3 getV2(){return vectorB;}
        public Vector3 getV3(){return vectorR;}

        public VertexPositionColor[] getVertex1( )
        { 
            return verts1;
        } 
        public VertexPositionColor[] getVertex2()
        {
            return verts2;
        }
        public VertexPositionColor[] getVertex3()
        {
            return verts3;
        }
    }
}

      

        
        
        
      

    

strange thing: verts1, vertes2, verts3 always get null after exiting the function. so the getters method that I called after execution always returns null.

what should i do guys?

this is my call to getters

math.calculate(v1, v2);
verts1 = math.getVertex1();
verts2 = math.getVertex2();
verts3 = math.getVertex3();