在Visual Studio中建立一個進度條控制項

Create a custom ProgressBar control

1. Follow these steps to create a new Windows Control Library project in Visual C#:
   1. Start Microsoft Visual Studio.
   2. On the File menu, point to New, and then click Project.
   3. In the New Project dialog box, click Visual C# under Project Types, and then click Windows Forms Control Library under Templates.

      Note In Visual Studio .NET 2003, click Visual C# Projects instead of Visual C#.

   4. In the Name box, type SmoothProgressBar, and then click OK.
   5. In Project Explorer, rename the default class module from UserControl1.cs to SmoothProgressBar.cs.
   6. In the Properties window for the UserControl object, change the Name property from UserControl1 to SmoothProgressBar.

COMMENT: These steps show us how to create a customized control.

 

　2. At this point, you typically inherit from the class of that control and then add the additional functionality to extend an existing control. However, the ProgressBar class is sealed and cannot be inherited. Therefore, you must build the control from the beginning.

COMMETS: The deleted line seems to have no meaning at all. Please note the ProgressBar is sealed. A sealed class cannot be inherited.

Add the following code to the SmoothProgressBar.cs file, in the class that is derived from UserControl.

 

int min = 0;// Minimum value for progress rangeint max = 100;// Maximum value for progress rangeint val = 0;// Current progressColor BarColor = Color.Blue;// Color of progress meterprotected override void OnResize(EventArgs e){// Invalidate the control to get a repaint.this.Invalidate();}protected override void OnPaint(PaintEventArgs e){Graphics g = e.Graphics;SolidBrush brush = new SolidBrush(BarColor);float percent = (float)(val - min) / (float)(max - min);Rectangle rect = this.ClientRectangle;// Calculate area for drawing the progress.rect.Width = (int)((float)rect.Width * percent);// Draw the progress meter.g.FillRectangle(brush, rect);// Draw a three-dimensional border around the control.Draw3DBorder(g);// Clean up.brush.Dispose();g.Dispose();}public int Minimum{get{return min;}set{// Prevent a negative value.if (value < 0){min = 0;}// Make sure that the minimum value is never set higher than the maximum value.if (value > max){min = value;min = value;}// Ensure value is still in rangeif (val < min){val = min;}// Invalidate the control to get a repaint.this.Invalidate();}}public int Maximum{get{return max;}set{// Make sure that the maximum value is never set lower than the minimum value.if (value < min){min = value;}max = value;// Make sure that value is still in range.if (val > max){val = max;}// Invalidate the control to get a repaint.this.Invalidate();}}public int Value{get{return val;}set{int oldValue = val;// Make sure that the value does not stray outside the valid range.if (value < min){val = min;}else if (value > max){val = max;}else{val = value;}// Invalidate only the changed area.float percent;Rectangle newValueRect = this.ClientRectangle;Rectangle oldValueRect = this.ClientRectangle;// Use a new value to calculate the rectangle for progress.percent = (float)(val - min) / (float)(max - min);newValueRect.Width = (int)((float)newValueRect.Width * percent);// Use an old value to calculate the rectangle for progress.percent = (float)(oldValue - min) / (float)(max - min);oldValueRect.Width = (int)((float)oldValueRect.Width * percent);Rectangle updateRect = new Rectangle();// Find only the part of the screen that must be updated.if (newValueRect.Width > oldValueRect.Width){updateRect.X = oldValueRect.Size.Width;updateRect.Width = newValueRect.Width - oldValueRect.Width;}else{updateRect.X = newValueRect.Size.Width;updateRect.Width = oldValueRect.Width - newValueRect.Width;}updateRect.Height = this.Height;// Invalidate the intersection region only.this.Invalidate(updateRect);}}public Color ProgressBarColor{get{return BarColor;}set{BarColor = value;// Invalidate the control to get a repaint.this.Invalidate();}}private void Draw3DBorder(Graphics g){int PenWidth = (int)Pens.White.Width;g.DrawLine(Pens.DarkGray, new Point(this.ClientRectangle.Left, this.ClientRectangle.Top),new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Top));g.DrawLine(Pens.DarkGray,new Point(this.ClientRectangle.Left, this.ClientRectangle.Top), new Point(this.ClientRectangle.Left, this.ClientRectangle.Height - PenWidth));g.DrawLine(Pens.White,new Point(this.ClientRectangle.Left, this.ClientRectangle.Height - PenWidth), new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Height - PenWidth));g.DrawLine(Pens.White,new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Top), new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Height - PenWidth));}