无法使System.Drawing.Graphics在窗体中工作 [英] Trouble Getting System.Drawing.Graphics to work in Form

问题描述

我试图在Visual Studio中制作一个C＃Windows窗体，以便可以在该窗体上绘制（就像Microsoft Paint的基本版本一样）。我正在研究C＃2012本书中的示例。我已经按原样编写了代码，但是当我构建并运行该程序时，实际上无法在表单上绘制任何内容。代码成功编译，没有任何错误。谁能看到代码可以改进的地方，以便我可以成功地使用表格？

 使用系统； 
使用System.Collections.Generic; 
使用System.ComponentModel; 
使用System.Data; 
使用System.Drawing; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks; 
使用System.Windows.Forms; 
 
名称空间paint3 
 {
公共局部类Form1：表单
 {
 bool shouldPaint = false; 
 
 public Form1（）//构造函数
 {
 InitializeComponent（）; 
} 
 
 private void Form1_MouseDown（object sender，MouseEventArgs e）
 {
 shouldPaint = true; 
} 
 
 private void Form1_MouseUp（object sender，MouseEventArgs e）
 {
 shouldPaint = false; 
} 
 
 private void Form1_MouseMove（对象发送者，MouseEventArgs e）
 {
 if（shouldPaint）
 {
 using（Graphics graphics = CreateGraphics（））
 {
 graphics.FillEllipse（new SolidBrush（Color.BlueViolet），eX，eY，4，4）; 
} 
} 
} 
} 
} 
  

就Form1而言，它只是在Visual Studio 2012中单击新建Windows窗体应用程序时创建的空白窗体。我没有向Form1添加任何按钮，文本框或其他控件。

解决方案

  private void Form1_Paint（object sender，EventArgs e）
 {
 if（shouldPaint）
 {
 using（Graphics graphics = CreateGraphics（））
 {
 graphics.FillEllipse（new SolidBrush（Color.BlueViolet），eX，eY， 4，4）; 
} 
} 
} 
  

我正在尝试在Visual Studio中制作一个C＃Windows表单，以便可以在该表单上绘制（例如Microsoft Paint的
基本版本）。我正在通过
a C＃2012书中的示例进行研究。

Alex Fr在他的< href = http://www.codeproject.com/Articles/8494/DrawTools rel = nofollow noreferrer> DrawTools文章，这些工具可作为

我从以下位置获得的透明文本框： http://www.codeproject.com/Articles/4390/AlphaBlendTextBox-A-transparent-translucent-textbo

I am trying to make a C# Windows form in Visual Studio so I can draw on the form (like a basic version of Microsoft Paint). I am working through an example in a C# 2012 book. I have written the code verbatim, but when I build and run the program, I cannot actually draw anything on the form. The code compiles successfully without any errors. Can anyone see where the code can be improved so that I can successfully draw on the form?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace paint3
{
public partial class Form1 : Form
{
    bool shouldPaint = false;

    public Form1()  // constructor
    {
        InitializeComponent();
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        shouldPaint = true;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        shouldPaint = false;
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (shouldPaint)
        {
            using (Graphics graphics = CreateGraphics())
            {
                graphics.FillEllipse(new SolidBrush(Color.BlueViolet), e.X, e.Y, 4, 4);
            }
        }
    }
}
}

As far as Form1 is concerned, it's simply a blank form that is created when I click "New Windows Forms Application" in Visual Studio 2012. I haven't added any buttons, text boxes, or other controls to Form1.

解决方案

 private void Form1_Paint(object sender, EventArgs e)
    {
        if (shouldPaint)
        {
            using (Graphics graphics = CreateGraphics())
            {
                graphics.FillEllipse(new SolidBrush(Color.BlueViolet), e.X, e.Y, 4, 4);
            }
        }
    }

I am trying to make a C# Windows form in Visual Studio so I can draw on the form (like a basic version of Microsoft Paint). I am working through an example in a C# 2012 book.

Alex Fr provided an excellent set of drawing tools in his DrawTools article and these tools serve as a basis for Draw Tool Redux.

Here's a tool I recently wrote by adding to Draw Tool Redux, it creates Epilogs for Mathematica:

The EyeDropper Colour Picker I got from http://www.codeproject.com/Articles/36540/Adobe-Eyedropper-Control

The Transparent Textbox I got from: http://www.codeproject.com/Articles/4390/AlphaBlendTextBox-A-transparent-translucent-textbo

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