我想将一个矩形从一个Event函数传递给另一个Event函数 [英] I want to to pass a rectangle from one Event function to a second Event function

问题描述

我想将矩形从一个函数传递给第二个函数

由于某种原因，rectangel读取事件函数为null

我该怎么做？

I want to to pass a rectangle from one function to a second function
For some reason the rectangel read to the event function as null
How can I do this?

private Point startpoint;
        private Rectangle rect;
 
        private void canvas1_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
        {
            
            startpoint = Mouse.GetPosition(canvas1);
 
  // the rectengle that i creat and i what to pass him to the canvas1_MouseMove Event function 
            Rectangle rect = new Rectangle();
            rect.Stroke = Brushes.Black;
            rect.StrokeThickness = 1;
 

            canvas1.Children.Add(rect);
       
 

        }
 
        
 
        private void canvas1_MouseMove(object sender, MouseEventArgs e)
        {
           //to here i want to pass the rectangle  
           // when i debug the code the rect value is null!
           // so i cant control his Properties
 
 
                rect.Width = 5;// her i got excsption 
                               //"Object reference not set to an instance of an object."
                rect.Height = 6;
 
      
 
           
           
        }

推荐答案

A几点需要注意。首先是私人矩形矩形;和Rectangle rect = new Rectangle（）;将成为两个对象，第二个对象只是方法canvas1_MouseRightButtonDown。要解决这个问题，请删除第二个中的对象标识符，使其为rect = new Rectangle（）;。



第二个构建第一个，因为你需要在调用MouseMove事件之前初始化对象。两种想法取决于C＃的版本。将初始化放在方法之外：

private Rectangle rect = new Rectangle（）;

在版本4+中，我们在Java中也做了一些内部方法，类似于：

Rectangle rect = new Rectangle（）{

Stroke = Brushes.Black;

StrokeThickness = 1;

}

但是，一旦创建了对象，如果需要，可以在两种方法中重做Rectangle的某些特征。

A couple of things to note. The first is, "private Rectangle rect;" and "Rectangle rect = new Rectangle();" are going to be two objects, with the second being local only to the method "canvas1_MouseRightButtonDown". To rectify this, remove the object identifier in the second so it is "rect = new Rectangle();".

The second builds off the first in that you need to have the object initialized before the "MouseMove" event is called. Two thoughts depending upon the version of C#. Put the initialization outside of the methods:
private Rectangle rect = new Rectangle();
In version 4+ there is also something we do in Java to be an inner method, something like:
Rectangle rect = new Rectangle(){
Stroke = Brushes.Black;
StrokeThickness = 1;
}
however, once you have your object created, you can "redo" certain characteristics of the Rectangle in both methods if need be.

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