无法生成解决方案，提示应输入类型、命名空间定义或文件尾

代码如下:并且还提示当前上下文不存在m_enabled；m_app
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using ESRI.ArcGIS.SystemUI;
using ESRI.ArcGIS.Framework;
using ESRI.ArcGIS.ArcMapUI;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Geometry;

namespace MyZoomInAddinyxy
{
public class MyZoomInAddin : ESRI.ArcGIS.Desktop.AddIns.Button
{

    public class ZoomInCsharp : ICommand
       {
       
        private IApplication m_app;
        private bool m_enabled;
        private System.Drawing.Bitmap m_bitmap;
        private IntPtr m_hBitmap;
        }
       public void OnCreate(object hook)
        {
            if (hook != null)
            {
                if (hook is IMxApplication)
                {
                    m_app = (IApplication)hook;
                    m_enabled = true;
                }
            }
        }
        public  void OnClick()
        {
          
            IMxDocume