System.Drawing.Image.GetThumbnailImageAbort

[hongyanhua12]

我对委托不是很清楚，System.Drawing.Image.GetThumbnailImageAbort mycall = new System.Drawing.Image.GetThumbnailImageAbort(bool1);
是怎么用的？能举个简单的例子吗？
protected void Page_Load(object sender, EventArgs e)
{
System.Drawing.Image.GetThumbnailImageAbort mycall = new System.Drawing.Image.GetThumbnailImageAbort(bool1);
Bitmap image = new Bitmap(Session["filename"].ToString());
System.Drawing.Image image1 = image.GetThumbnailImage(80, 80, mycall, IntPtr.Zero);
image1.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
public bool bool1()
{
return false;
}

[hongyanhua12]

什么意思啊？还是不太明白

[hongyanhua12]

帮订一下啊

[hongqi162]

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace xmlandasp
{
  /// <summary>
  /// Summary description for MakeThumbnail.
  /// </summary>
  public class MakeThumbnail : System.Web.UI.Page
  {
  /// <summary>
  /// Renders the thumbnail the response stream
  /// </summary>
    private void Page_Load(object sender, System.EventArgs e)
    {
      System.Drawing.Image.GetThumbnailImageAbort myCallback =
        new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);
      
      System.Drawing.Image image = System.Drawing.Image.FromFile(Server.MapPath(Request.QueryString["file"]));

      System.Drawing.Image thumbNail = image.GetThumbnailImage(100, 80, myCallback, IntPtr.Zero);
      Response.ContentType = "image/jpeg";
      thumbNail.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Jpeg);
      image.Dispose();
      thumbNail.Dispose();      
    }

    /// <summary>
    /// Required, but not used
    /// </summary>
    /// <returns>true</returns>
    public bool ThumbnailCallback()
    {
      return false;
    }

    #region Web Form Designer generated code
    override protected void OnInit(EventArgs e)
    {
      InitializeComponent();
      base.OnInit(e);
    }
    
    private void InitializeComponent()
    {
      this.Load += new System.EventHandler(this.Page_Load);
    }
    #endregion
  }
}

[宝_爸]

你的代码就是使用委托的例子啊。委托的意思就是callback。

你可以把mycall 想象成一个函数对象，其构造函数的参数bool1的原型必须符合GetThumbnailImageAbort的声明，把mycall 作为参数传给GetThumbnailImage，在GetThumbnailImage内部会在适当的时候调用bool1。


下面是GetThumbnailImageAbort 的解释，因此你在GetThumbnailImageAbort(其实例的就是mycall) 中可以什么都不做，会不影响GetThumbnailImage的结果。
A Image.GetThumbnailImageAbort delegate. In GDI+ version 1.0, the delegate is not used. Even so, you must create a delegate and pass a reference to that delegate in this parameter.

[sxmonsy]

顶一下

[流年岁月]

mark 一下