2

我正在尝试编译我在此处找到的 TwainDotNet 解决方案(C# TWAIN 交互),但我束手无策。

这个解决方案显然是在 VS 2008 中开发的,我在 2005 年工作(目前别无选择)。2005 年我可能花了很多时间来编译这一切,并且我已经将我的错误减少到两个,两个错误都是同一个问题。

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;

namespace TwainDotNet.WinFroms
{
  /// <summary>
  /// A windows message hook for WinForms applications.
  /// </summary>
  public class WinFormsWindowMessageHook : IWindowsMessageHook, IMessageFilter
  {
    IntPtr _windowHandle;
    bool _usingFilter;

    public WinFormsWindowMessageHook(Form window)
    {
      _windowHandle = window.Handle;
    }

    public bool PreFilterMessage(ref Message m)
    {
      if (FilterMessageCallback != null)
      {
        bool handled = false;
        FilterMessageCallback(m.HWnd, m.Msg, m.WParam, m.LParam, ref handled);
        return handled;
      }

      return false;
    }

    public IntPtr WindowHandle { get { return _windowHandle; } }

    public bool UseFilter
    {
      get
      {
        return _usingFilter;
      }

      set
      {
        if (!_usingFilter && value == true)
        {
          Application.AddMessageFilter(this);
          _usingFilter = true;
        }

        if (_usingFilter && value == false)
        {
          Application.RemoveMessageFilter(this);
          _usingFilter = false;
        }
      }
    }

    public FilterMessage FilterMessageCallback 
    {
      get; 
      set;
    }
  }

}

在访问委托实例的属性上编译失败。

错误:“TwainDotNet.WinFroms.WinFormsWindowMessageHook.FilterMessageCallback.get”必须声明一个主体,因为它没有标记为抽象或外部

这是该类实现的接口 IWindowsMessageHook:

using System;
using System.Collections.Generic;
using System.Text;

namespace TwainDotNet
{
  public interface IWindowsMessageHook
  {
    /// <summary>
    /// Gets or sets if the message filter is in use.
    /// </summary>
    bool UseFilter { get; set; }

    /// <summary>
    /// The delegate to call back when the filter is in place and a message arrives.
    /// </summary>
    FilterMessage FilterMessageCallback { get; set; }

    /// <summary>
    /// The handle to the window that is performing the scanning.
    /// </summary>
    IntPtr WindowHandle { get; }
  }

  public delegate IntPtr FilterMessage(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled);
}

我承认自己是代表新手,我在这里不知所措。如何在 VS 2005 中复制此功能?

谢谢你的时间。

4

3 回答 3

0

一个事件可能是可取的,但作为一个委托属性:

private FilterMessage filterMessageCallback;
public FilterMessage FilterMessageCallback 
{
  get {return filterMessageCallback;}
  set { filterMessageCallback = value;}
}

为避免边缘情况(线程竞争 / null),您可能还需要:

public bool PreFilterMessage(ref Message m)
{
  FilterMessage callback = FilterMessageCallback;
  if (callback != null)
  {
    bool handled = false;
    callback(m.HWnd, m.Msg, m.WParam, m.LParam, ref handled);
    return handled;
  }

  return false;
}
于 2009-12-02T17:29:24.910 回答
0

填写属性声明中的空白——没有什么神奇的事情发生:

private FilterMessage _filterMessageCallback;

public FilterMessage FilterMessageCallback
{
    get { return _filterMessageCallback; }
    set { _filterMessageCallback = value; }
}
于 2009-12-02T17:30:32.417 回答
0

只需使用支持字段:

private FilterMessage m_FilterMessageCallback;
public FilterMessage FilterMessageCallback 
{
  get { return m_FilterMessageCallback; }
  set { m_FilterMessageCallback = value; }
}

界面中的代码

FilterMessage FilterMessageCallback { get; set; }

顺便说一句。与 C#2.0/3.0 无关,这是一个带有 setter 和 getter 的普通接口定义。

于 2009-12-02T17:30:32.683 回答