事件处理程序

Question

我真的很新的WinForms和此刻的我有以下的错误使用的事件处理程序在C＃：

Error 1 The type 'DotFlickScreenCapture.ScreenCapture' cannot be used as type parameter 'TEventArgs' in the generic type or method 'System.EventHandler'. There is no implicit reference conversion from 'DotFlickScreenCapture.ScreenCapture' to 'System.EventArgs'.

我试图寻找一种方法来打败这个错误，但到目前为止，我的谷歌搜索没有发现任何东西。

线这个错误点是这个：

public EventHandler<ScreenCapture> capture; 

，从我可以告诉，这个类：

public class ScreenCapture 
{ 
    public delegate void StatusUpdateHandler(object sender, ProgressEventArgs e); 
    public event StatusUpdateHandler OnUpdateStatus; 

    public bool saveToClipboard = true; 

    public void CaptureImage(bool showCursor, Size curSize, Point curPos, Point SourcePoint, Point DestinationPoint, Rectangle SelectionRectangle, string FilePath, string extension) 
    { 
     Bitmap bitmap = new Bitmap(SelectionRectangle.Width, SelectionRectangle.Height); 

     using (Graphics g = Graphics.FromImage(bitmap)) 
     { 
      g.CopyFromScreen(SourcePoint, DestinationPoint, SelectionRectangle.Size); 

      if (showCursor) 
      { 
       Rectangle cursorBounds = new Rectangle(curPos, curSize); 
       Cursors.Default.Draw(g, cursorBounds); 
      } 
     } 

     if (saveToClipboard) 
     { 

      Image img = (Image)bitmap; 
      Clipboard.SetImage(img); 

      if (OnUpdateStatus == null) return; 

      ProgressEventArgs args = new ProgressEventArgs(img); 
      OnUpdateStatus(this, args); 
     } 
     else 
     { 
      switch (extension) 
      { 
       case ".bmp": 
        bitmap.Save(FilePath, ImageFormat.Bmp); 
        break; 
       case ".jpg": 
        bitmap.Save(FilePath, ImageFormat.Jpeg); 
        break; 
       case ".gif": 
        bitmap.Save(FilePath, ImageFormat.Gif); 
        break; 
       case ".tiff": 
        bitmap.Save(FilePath, ImageFormat.Tiff); 
        break; 
       case ".png": 
        bitmap.Save(FilePath, ImageFormat.Png); 
        break; 
       default: 
        bitmap.Save(FilePath, ImageFormat.Jpeg); 
        break; 
      } 
     } 
    } 
} 


public class ProgressEventArgs : EventArgs 
{ 
    public Image CapturedImage { get; private set; } 
    public ProgressEventArgs(Image img) 
    { 
     CapturedImage = img; 
    } 
} 

有没有人经历过这个错误？是的，我如何克服它？

Answer 1

ScreenCapture类必须从EventArgs类派生出来才能以您想要的方式使用。

public class ScreenCapture : EventArgs 

然后（避免误解），它应该被命名ScreenCaptureEventArgs。考虑到这一点，创建一个ScreenCaptureEventArgs的类将更容易，该类衍生自EventArgs并且包含属性ScreenCapture，这是您已拥有的类的实例。

就像是：

public class ScreenCaptureEventArgs : EventArgs 
{ 
    public ScreenCaptureEventArgs(ScreenCapture c) 
    { 
     Capture = c; 
    } 

    public ScreenCapture Capture { get; private set; } 
} 

public event EventHandler<ScreenCaptureEventArgs> ScreenCaptured;