Mesh tempMesh = Mesh.Clean(mesh, adj, adj);

     simplifiedMesh = Mesh.Simplify(mesh, adj, null, 1, MeshFlags.SimplifyVertex);

private void LoadMesh(string file)
{
     ExtendedMaterial[] mtrl;
     GraphicsStream adj;

     // Load our mesh
     mesh = Mesh.FromFile(file, MeshFlags.Managed, device, out adj, out mtrl);

     // If we have any materials, store them
     if ((mtrl != null) && (mtrl.Length > 0))
     {
         meshMaterials = new Material[mtrl.Length];
         meshTextures = new Texture[mtrl.Length];

         // Store each material and texture
         for (int i = 0; i < mtrl.Length; i++)
         {
              meshMaterials = mtrl.Material3D;
              if ((mtrl.TextureFilename != null) && (mtrl.TextureFilename != string.Empty))
              {
                   // We have a texture, try to load it
                   meshTextures = TextureLoader.FromFile(device, @"..\..\" + mtrl.TextureFilename);
              }
         }
      }

      // Clean our main mesh
      Mesh tempMesh = Mesh.Clean(mesh, adj, adj);
            // Replace our existing mesh with this one
      mesh.Dispose();
      mesh = tempMesh;

      // Get our new simplified mesh
      simplifiedMesh = Mesh.Simplify(mesh, adj, null, 1, MeshFlags.SimplifyVertex);

      // Save our simplified mesh for later use
      // First we need to generate the adjacency for this mesh
      int[] simpleAdj = new int[simplifiedMesh.NumberFaces * 3];
      simplifiedMesh.GenerateAdjacency(0.0f, simpleAdj);
      using (Mesh cleanedMesh = Mesh.Clean(CleanType.Simplification, simplifiedMesh,simpleAdj, out simpleAdj))
      {
          cleanedMesh.Save(@"..\..\simple.x", simpleAdj, 
                    mtrl, XFileFormat.Text);
      }
      Console.WriteLine("Number of vertices in original mesh: {0}", mesh.NumberVertices);
      Console.WriteLine("Number of vertices in simplified mesh: {0}", simplifiedMesh.NumberVertices);
}

From:// Clean our main meshMesh tempMesh = Mesh.Clean(mesh, adj, adj);To:// Clean our main meshMesh tempMesh = Mesh.Clean(CleanType.Simplification, mesh, adj, adj);

// Get our new simplified meshsimplifiedMesh = Mesh.Simplify(mesh, adj, null, 1, MeshFlags.SimplifyVertex);It returns the following error:System.AccessViolationException was unhandled  Message="Attempted to read or write protected memory. This is often an indication that other memory is corrupt."  Source="Microsoft.DirectX.Direct3DX"  StackTrace:       at D3DXSimplifyMesh(ID3DXMesh* , UInt32* , _D3DXATTRIBUTEWEIGHTS* , Single* , UInt32 , UInt32 , ID3DXMesh** )       at Microsoft.DirectX.Direct3D.Mesh.SimplifyMeshInternal(Mesh mesh, IntPtr adjacency, AttributeWeights& vertexAttributeWeights, IntPtr vertexWeights, Int32 minValue, MeshFlags options)       at Microsoft.DirectX.Direct3D.Mesh.Simplify(Mesh mesh, GraphicsStream adjacency, GraphicsStream vertexWeights, Int32 minValue, MeshFlags options)       at Chapter7Code.Form1.LoadMesh(String file) in C:\Program Files\Sams Publishing\MDXKickStart\C# Code\Chapter 7\SimplifyMesh\Form1.cs:line 94       at Chapter7Code.Form1.InitializeGraphics() in C:\Program Files\Sams Publishing\MDXKickStart\C# Code\Chapter 7\SimplifyMesh\Form1.cs:line 58       at Chapter7Code.Form1.Main() in C:\Program Files\Sams Publishing\MDXKickStart\C# Code\Chapter 7\SimplifyMesh\Form1.cs:line 217       at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)       at System.Threading.ThreadHelper.ThreadStart()