Memory Error, too

I wrote a code imitating the tutorial program in this forum, trying to let vtkformwindow display a single dicom image. But when the function is called, I get an exception
"An unhandled exception of type 'System.AccessViolationException' occurred in vtkRenderingDotNet.dll"
and the following information:
"Attempt to read or write protected memory. This is often an indication that ohter memory is corrupt.  At vtk.vtkRenderWindow.Render()"

What is strange is that the same code in C++ grammar can run correctly in native VTK and VC++6.0 environment. And when I use vtkBMPImageReader, it is OK too. Anyone who has idea what happens here? Thanks a lot.This is graduation project.

Here is my code:

-----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using vtk;

namespace VTKtest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.AddConeToWindow(this.VTKform.GetRenderWindow());
            this.AddConeToWindow(this.vtkForm2.GetRenderWindow());
        }

        void AddConeToWindow(vtk.vtkRenderWindow renWin)
        {
            vtk.vtkConeSource cone = new vtk.vtkConeSource();
            cone.SetHeight(3.0f);
            cone.SetRadius(1.0f);
            cone.SetResolution(30);

            vtk.vtkPolyDataMapper coneMapper = new vtk.vtkPolyDataMapper();
            coneMapper.SetInput(cone.GetOutput());

            vtk.vtkActor coneActor = new vtk.vtkActor();
            coneActor.SetMapper(coneMapper);

            vtk.vtkRenderer ren1 = new vtk.vtkRenderer();
            ren1.AddActor(coneActor);
            ren1.SetBackground(0.0f, 0.0f, 0.0f);
            renWin.AddRenderer(ren1);
        }

        void AddDicomToWindow(vtk.vtkRenderWindow renWin)
        {
            try
            {
                vtkDICOMImageReader reader = new vtkDICOMImageReader();

                reader.SetFileName("C:/MedData/Import1/SIMON_10.dcm");
                reader.SetDataByteOrderToLittleEndian();

                vtkImageData image1 = new vtkImageData();
                image1 = reader.GetOutput();

                vtkImageMapper mapper1 = new vtkImageMapper();
                mapper1.SetInput(image1);

                vtkActor2D actor1 = new vtkActor2D();
                actor1.SetMapper(mapper1);

                vtkRenderer ren = new vtkRenderer();
                ren.AddActor2D(actor1);
                renWin.AddRenderer(ren);

                renWin.SetSize(vtkForm4.Size.Width, vtkForm4.Size.Height);
                vtkRenderWindowInteractor iren = new vtkRenderWindowInteractor();

                iren.SetRenderWindow(renWin);
                renWin.Render();//

                iren.Initialize();
                iren.Start();
                //renWin.Dispose();

            }
            catch (Exception e)
            {
               // MessageBox.Show(e.Message + "\n" + e.StackTrace);
            }

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.AddDicomToWindow(this.vtkForm4.GetRenderWindow());
        }

    }
}