[C#]WinForm Label 透明底色

C#的Winform不支援底色透明的Label(Button也一樣)
雖然在物件屬性上可以選擇底色為透明，但其透明仍以Winform底色為主(Label透明=Winform的顏色)

所以參考了人家的做法，在此做了紀錄，並加上詳細的使用方式

1.在專案上新增類別(類別名稱:TransparentLabel )，將下列程式碼貼上
2.在Form設計模式底下點選工具箱，即會出現該類別所產生的Label，將其拖拉到Form上
3.修改該物件的屬性(跟一般使用Label一樣)
4.注意一點，只要Label的背景有變，就要執行Refesh()

有空再來做範例

==========在專案上新增類別(類別名稱:TransparentLabel )，將下列程式碼貼上=======

using System;
using System.Drawing;
using System.Windows.Forms;

namespace WinFormsControls
{
  /// 

  /// A label that can be transparent.
  /// 
  public class TransparentLabel : Control
  {
    /// 

    /// Creates a new  instance.
    /// 
    public TransparentLabel()
    {
      TabStop = false;
    }

    /// 

    /// Gets the creation parameters.
    /// 
    protected override CreateParams CreateParams
    {
      get
      {
        CreateParams cp = base.CreateParams;
        cp.ExStyle |= 0x20;
        return cp;
      }
    }

    /// 

    /// Paints the background.
    /// 
    /// E.    protected override void OnPaintBackground(PaintEventArgs e)
    {
      // do nothing
    }

    /// 

    /// Paints the control.
    /// 
    /// E.    protected override void OnPaint(PaintEventArgs e)
    {
      DrawText();
    }

    protected override void WndProc(ref Message m)
    {
      base.WndProc(ref m);
      if (m.Msg == 0x000F)
      {
        DrawText();
      }
    }

    private void DrawText()
    {
      using (Graphics graphics = CreateGraphics())
      using (SolidBrush brush = new SolidBrush(ForeColor))
      {
        SizeF size = graphics.MeasureString(Text, Font);

        // first figure out the top
        float top = 0;
        switch (textAlign)
        {
          case ContentAlignment.MiddleLeft:
          case ContentAlignment.MiddleCenter:
          case ContentAlignment.MiddleRight:
            top = (Height - size.Height) / 2;
            break;
          case ContentAlignment.BottomLeft:
          case ContentAlignment.BottomCenter:
          case ContentAlignment.BottomRight:
            top = Height - size.Height;
            break;
        }

        float left = -1;
        switch (textAlign)
        {
          case ContentAlignment.TopLeft:
          case ContentAlignment.MiddleLeft:
          case ContentAlignment.BottomLeft:
            if (RightToLeft == RightToLeft.Yes)
              left = Width - size.Width;
            else
              left = -1;
            break;
          case ContentAlignment.TopCenter:
          case ContentAlignment.MiddleCenter:
          case ContentAlignment.BottomCenter:
            left = (Width - size.Width) / 2;
            break;
          case ContentAlignment.TopRight:
          case ContentAlignment.MiddleRight:
          case ContentAlignment.BottomRight:
            if (RightToLeft == RightToLeft.Yes)
              left = -1;
            else
              left = Width - size.Width;
            break;
        }
        graphics.DrawString(Text, Font, brush, left, top);
      }
    }

    /// 

    /// Gets or sets the text associated with this control.
    /// 
    /// 
    /// The text associated with this control.
    /// 
    public override string Text
    {
      get
      {
        return base.Text;
      }
      set
      {
        base.Text = value;
        RecreateHandle();
      }
    }

    /// 

    /// Gets or sets a value indicating whether control's elements are aligned to support locales using right-to-left fonts.
    /// 
    /// 
    /// 
    /// One of the  values. The default is .
    /// 
    /// 
    /// The assigned value is not one of the  values.
    /// 
    public override RightToLeft RightToLeft
    {
      get
      {
        return base.RightToLeft;
      }
      set
      {
        base.RightToLeft = value;
        RecreateHandle();
      }
    }

    /// 

    /// Gets or sets the font of the text displayed by the control.
    /// 
    /// 
    /// 
    /// The  to apply to the text displayed by the control. The default is the value of the  property.
    /// 
    public override Font Font
    {
      get
      {
        return base.Font;
      }
      set
      {
        base.Font = value;
        RecreateHandle();
      }
    }

    private ContentAlignment textAlign = ContentAlignment.TopLeft;
    /// 

    /// Gets or sets the text alignment.
    /// 
    public ContentAlignment TextAlign
    {
      get { return textAlign; }
      set
      {
        textAlign = value;
        RecreateHandle();
      }
    }
  }
}