爲什麼在構造函數的窗體上繪製不在窗體上顯示任何東西？

Question

編輯：這不是「如何在C＃中使用OnPaint事件」的重複，因爲我甚至不知道它存在。當我不知道答案時，我在問一個問題。這就像問我「我怎麼檢查我車裏的油」，當我甚至不知道浸漬棒是什麼。請刪除重複標誌，如果這樣做可以解釋爲什麼它不是重複的。

我想製作一個隨機地形生成器。目前，我正在使用Windows Forms圖形繪製所有圖形。我似乎無法讓引擎工作。運行下面的代碼不會在窗體上顯示任何內容，即使它應該從0,0到50,50繪製一個黑色的矩形。誰能解決？

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 Random_Terrain_Generator 
{ 
    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 

      Engine e = new Engine(100, 100); 
      e.Color3(Color.Blue); 
      e.rect(new Rectangle(0,0,50,50)); 
      Graphics fg = this.CreateGraphics(); 
      fg.DrawImage(e.getBuffer(), 1, 100, 100, 100); 
     } 
    } 

    public class Engine 
    { 
     Color fillColor; 
     Bitmap buffer; 
     Graphics bufferGraphics; 

     public Engine(int bufferWidth, int bufferHeight) 
     { 
      buffer = new Bitmap(bufferWidth, bufferHeight); 
      bufferGraphics = Graphics.FromImage(buffer); 
     } 

     public void fRect(Rectangle r) 
     { 
      bufferGraphics.FillRectangle(new SolidBrush(fillColor), r); 
     } 

     public void rect(Rectangle r) 
     { 
      bufferGraphics.DrawRectangle(new Pen(fillColor), r); 
     } 

     public void Color3(Color c) 
     { 
      fillColor = c; 
     } 

     public Bitmap getBuffer() 
     { 
      return buffer; 
     } 
    } 
} 

Answer 1

這工作！感謝TyCobb的快速回答。

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 Random_Terrain_Generator 
{ 
    public partial class Form1 : Form 
    { 
     Engine e; 

     public Form1() 
     { 
      InitializeComponent(); 

      e = new Engine(100, 100); 
      e.Color3(Color.Blue); 
      e.fRect(new Rectangle(0,0,50,50)); 
     } 

     protected override void OnPaint(PaintEventArgs pe) 
     { 
      // Call the OnPaint method of the base class. 
      base.OnPaint(pe); 
      pe.Graphics.DrawImage(e.getBuffer(), 1, 1, 100, 100); 

     } 
    } 

    public class Engine 
    { 
     Color fillColor; 
     Bitmap buffer; 
     Graphics bufferGraphics; 

     public Engine(int bufferWidth, int bufferHeight) 
     { 
      buffer = new Bitmap(bufferWidth, bufferHeight); 
      bufferGraphics = Graphics.FromImage(buffer); 
     } 

     public void fRect(Rectangle r) 
     { 
      bufferGraphics.FillRectangle(new SolidBrush(fillColor), r); 
     } 

     public void rect(Rectangle r) 
     { 
      bufferGraphics.DrawRectangle(new Pen(fillColor), r); 
     } 

     public void Color3(Color c) 
     { 
      fillColor = c; 
     } 

     public Bitmap getBuffer() 
     { 
      return buffer; 
     } 
    } 
} 

我重寫窗體的OnPaint事件，它重繪每個框架的矩形。問題在於表單畫在矩形上。 How to use the OnPaint event in C#?