背景

对于.NET 原本提供的DataGridView控件，制作成如下形式的表格是毫无压力的。

但是如果把表格改了一下，变成如下形式

传统的DataGridView就做不到了，如果扩展一下还是行的，有不少网友也扩展了DataGridView控件，不过有些也只能制作出二维的表头。或者使用第三方的控件，之前也用过DevExpress的BoundGridView。不过在没有可使用的第三方控件的情况下，做到下面的效果，就有点麻烦了。

那得自己扩展了，不过最后还是用了一个控件库的报表控件，Telerik的Reporting。不过我自己还是扩展了DataGridView，使之能制作出上面的报表。

准备

学习了一些网友的代码，原来制作这个多维表头都是利用GDI+对DataGirdView的表头进行重绘。

用到的方法包括

Graphics.FillRectangle //填充一个矩形

Graphics.DrawLine //画一条线

Graphics.DrawString  //写字符串

此外为了方便组织表头，本人还定义了一个表头的数据结构 HeaderItem 和 HeaderCollection 分别作为每个表头单元格的数据实体和整个表头的集合。

HeaderItem的定义如下

复制代码 代码如下:
public class HeaderItem
     {
         private int _startX;//起始横坐标
         private int _startY;//起始纵坐标
         private int _endX; //终止横坐标
         private int _endY; //终止纵坐标
         private bool _baseHeader; //是否基础表头

         public HeaderItem(int startX, int endX, int startY, int endY, string content)
         {
             this._endX = endX;
             this._endY = endY;
             this._startX = startX;
             this._startY = startY;
             this.Content = content;
         }

         public HeaderItem(int x, int y, string content):this(x,x,y,y,content)
         {

         }

         public HeaderItem()
         {

         }

         public static HeaderItem CreateBaseHeader(int x,int y,string content)
         {
             HeaderItem header = new HeaderItem();
             header._endX= header._startX = x;
             header._endY= header._startY = y;
             header._baseHeader = true;
             header.Content = content;
             return header;
         }

         public int StartX
         {
             get { return _startX; }
             set
             {
                 if (value > _endX)
                 {
                     _startX = _endX;
                     return;
                 }
                 if (value < 0) _startX = 0;
                 else _startX = value;
             }
         }

         public int StartY
         {
             get { return _startY; }
             set
             {
                 if (_baseHeader)
                 {
                     _startY = 0;
                     return;
                 }
                 if (value > _endY)
                 {
                     _startY = _endY;
                     return;
                 }
                 if (value < 0) _startY = 0;
                 else _startY = value;
             }
         }

         public int EndX
         {
             get { return _endX; }
             set
             {
                 if (_baseHeader)
                 {
                     _endX = _startX;
                     return;
                 }
                 if (value < _startX)
                 {
                     _endX = _startX;
                     return;
                 }
                 _endX = value;
             }
         }

         public int EndY
         {
             get { return _endY; }
             set
             {
                 if (value < _startY)
                 {
                     _endY = _startY;
                     return;
                 }
                 _endY = value;
             }
         }

         public bool IsBaseHeader
         {get{ return _baseHeader;} }

         public string Content { get; set; }
     }

设计思想是利用数学的直角坐标系，给每个表头单元格定位并划定其大小。与计算机显示的坐标定位不同，这里的原点是跟数学的一样放在左下角，X轴正方向是水平向右，Y轴正方向是垂直向上。如下图所示

之所以要对GridView中原始的列头进行特别处理，是因为这里的起止坐标和终止坐标都可以设置，而原始列头的起始纵坐标（StartY）只能是0，终止横坐标（EndX）必须与起始横坐标（StartY）相等。

另外所有列头单元格的集合HeaderCollection的定义如下
复制代码 代码如下:
public class HeaderCollection
     {
         private List<HeaderItem> _headerList;
         private bool _iniLock;

         public DataGridViewColumnCollection BindCollection{get;set;}

         public HeaderCollection(DataGridViewColumnCollection cols)
         {
             _headerList = new List<HeaderItem>();
             BindCollection=cols;
             _iniLock = false;
         }

         public int GetHeaderLevels()
         {
             int max = 0;
             foreach (HeaderItem item in _headerList)
                 if (item.EndY > max)
                     max = item.EndY;

             return max;
         }

         public List<HeaderItem> GetBaseHeaders()
         {
             List<HeaderItem> list = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.IsBaseHeader) list.Add(item);
             return list;
         }

         public HeaderItem GetHeaderByLocation(int x, int y)
         {
             if (!_iniLock) InitHeader();
             HeaderItem result=null;
             List<HeaderItem> temp = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.StartX <= x && item.EndX >= x)
                     temp.Add(item);
             foreach (HeaderItem item in temp)
                 if (item.StartY <= y && item.EndY >= y)
                     result = item;

             return result;
         }

         public IEnumerator GetHeaderEnumer()
         {
             return _headerList.GetEnumerator();
         }

         public void AddHeader(HeaderItem header)
         {
             this._headerList.Add(header);
         }

         public void AddHeader(int startX, int endX, int startY, int endY, string content)
         {
             this._headerList.Add(new HeaderItem(startX,endX,startY,endY,content));
         }

         public void AddHeader(int x, int y, string content)
         {
             this._headerList.Add(new HeaderItem(x, y, content));
         }

         public void RemoveHeader(HeaderItem header)
         {
             this._headerList.Remove(header);
         }

         public void RemoveHeader(int x, int y)
         {
            HeaderItem header= GetHeaderByLocation(x, y);
            if (header != null) RemoveHeader(header);
         }

         private void InitHeader()
         {
             _iniLock = true;
             for (int i = 0; i < this.BindCollection.Count; i++)
                 if(this.GetHeaderByLocation(i,0)==null)
                 this._headerList.Add(HeaderItem.CreateBaseHeader(i,0 , this.BindCollection[i].HeaderText));
             _iniLock = false;
         }
     }

这里仿照了.NET Frameword的Collection那样定义了Add方法和Remove方法，此外说明一下那个 GetHeaderByLocation 方法，这个方法可以通过给定的坐标获取那个坐标的HeaderItem。这个坐标是忽略了整个表头合并单元格的情况，例如

上面这幅图，如果输入0，0 返回的是灰色区域，输入2，1 或3，2 或 5，1返回的都是橙色的区域。

扩展控件

到真正扩展控件了，最核心的是重写 OnCellPainting 方法，这个其实是与表格单元格重绘时触发事件绑定的方法，通过参数 DataGridViewCellPaintingEventArgs 的 ColumnIndex 和 RowIndex 属性可以知道当前重绘的是哪个单元格，于是就通过HeaderCollection获取要绘制的表头单元格的信息进行重绘，对已经重绘的单元格会进行标记，以防重复绘制。
复制代码 代码如下:
protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
         {
             if (e.ColumnIndex == -1 || e.RowIndex != -1)
             {
                 base.OnCellPainting(e);
                 return;
             }
             int lev=this.Headers.GetHeaderLevels();
             this.ColumnHeadersHeight = (lev + 1) * _baseColumnHeadHeight;
             for (int i = 0; i <= lev; i++)
             {
                 HeaderItem tempHeader= this.Headers.GetHeaderByLocation(e.ColumnIndex, i);
                 if (tempHeader==null|| i != tempHeader.EndY || e.ColumnIndex != tempHeader.StartX) continue;
                 DrawHeader(tempHeader, e);
             }
             e.Handled = true;
         }

上面的代码中，最初是先判断当前要重绘的单元格是不是表头部分，如果不是则调用原本的OnCellPainting方法。 e.Handled=true; 比较关键，有了这句代码，重绘才能生效。

绘制单元格的过程封装在方法DrawHeader里面

复制代码 代码如下:
private void DrawHeader(HeaderItem item,DataGridViewCellPaintingEventArgs e)
         {
             if (this.ColumnHeadersHeightSizeMode != DataGridViewColumnHeadersHeightSizeMode.DisableResizing)
                 this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             int lev=this.Headers.GetHeaderLevels();
             lev=(lev-item.EndY)*_baseColumnHeadHeight;

             SolidBrush backgroundBrush = new SolidBrush(e.CellStyle.BackColor);
             SolidBrush lineBrush = new SolidBrush(this.GridColor);
             Pen linePen = new Pen(lineBrush);
             StringFormat foramt = new StringFormat();
             foramt.Alignment = StringAlignment.Center;
             foramt.LineAlignment = StringAlignment.Center;

             Rectangle headRec = new Rectangle(e.CellBounds.Left, lev, ComputeWidth(item.StartX, item.EndX)-1, ComputeHeight(item.StartY, item.EndY)-1);
             e.Graphics.FillRectangle(backgroundBrush, headRec);
             e.Graphics.DrawLine(linePen, headRec.Left, headRec.Bottom, headRec.Right, headRec.Bottom);
             e.Graphics.DrawLine(linePen, headRec.Right, headRec.Top, headRec.Right, headRec.Bottom);
             e.Graphics.DrawString(item.Content, this.ColumnHeadersDefaultCellStyle.Font, Brushes.Black,headRec, foramt);
         }

填充矩形时，记得要给矩形的常和宽减去一个像素，这样才不会与相邻的矩形重叠区域导致矩形的边线显示不出来。还有这里的要设置 ColumnHeadersHeightSizeMode 属性，如果不把它设成 DisableResizing ，那么表头的高度是改变不了的，这样即使设置了二维，三维，n维，最终只是一维。

这里用到的一些辅助方法如下，分别是通过坐标计算出高度和宽度。

复制代码 代码如下:
private int ComputeWidth(int startX, int endX)
         {
             int width = 0;
             for (int i = startX; i <= endX; i++)
                 width+= this.Columns[i].Width;
             return width;
         }

         private int ComputeHeight(int startY, int endY)
         {
             return _baseColumnHeadHeight * (endY - startY+1);
         }

给一段使用的实例代码，这里要预先给DataGridView每一列设好绑定的字段，否则自动添加的列是做不出效果来的。

复制代码 代码如下:
HeaderItem item= this.boundGridView1.Headers.GetHeaderByLocation(0, 0);
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(9,0 );
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(10, 0);
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(11, 0);
             item.EndY = 2;

             this.boundGridView1.Headers.AddHeader(1, 2, 1, 1, "语文");
             this.boundGridView1.Headers.AddHeader(3, 4, 1, 1, "数学");
             this.boundGridView1.Headers.AddHeader(5, 6, 1, 1, "英语");
             this.boundGridView1.Headers.AddHeader(7, 8, 1, 1, "X科");
             this.boundGridView1.Headers.AddHeader(1, 8, 2, 2, "成绩");

效果图如下所示

总的来说自我感觉有点小题大做，但想不出有什么更好的办法，各位如果觉得以上说的有什么不好的，欢迎拍砖；如果发现以上有什么说错了，恳请批评指正；如果觉得好的，请支持一下。谢谢！最后附上整个控件的源码
控件的完整代码
复制代码 代码如下:

     public class BoundGridView : DataGridView
     {
         private int _baseColumnHeadHeight;

         public BoundGridView():base()
         {
             this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             _baseColumnHeadHeight = this.ColumnHeadersHeight;
             this.Headers = new HeaderCollection(this.Columns);
         }

         public HeaderCollection Headers{ get;private set; }

         protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
         {
             if (e.ColumnIndex == -1 || e.RowIndex != -1)
             {
                 base.OnCellPainting(e);
                 return;
             }
             int lev=this.Headers.GetHeaderLevels();
             this.ColumnHeadersHeight = (lev + 1) * _baseColumnHeadHeight;
             for (int i = 0; i <= lev; i++)
             {
                 HeaderItem tempHeader= this.Headers.GetHeaderByLocation(e.ColumnIndex, i);
                 if (tempHeader==null|| i != tempHeader.EndY || e.ColumnIndex != tempHeader.StartX) continue;
                 DrawHeader(tempHeader, e);
             }
             e.Handled = true;
         }

         private int ComputeWidth(int startX, int endX)
         {
             int width = 0;
             for (int i = startX; i <= endX; i++)
                 width+= this.Columns[i].Width;
             return width;
         }

         private int ComputeHeight(int startY, int endY)
         {
             return _baseColumnHeadHeight * (endY - startY+1);
         }

         private void DrawHeader(HeaderItem item,DataGridViewCellPaintingEventArgs e)
         {
             if (this.ColumnHeadersHeightSizeMode != DataGridViewColumnHeadersHeightSizeMode.DisableResizing)
                 this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             int lev=this.Headers.GetHeaderLevels();
             lev=(lev-item.EndY)*_baseColumnHeadHeight;

             SolidBrush backgroundBrush = new SolidBrush(e.CellStyle.BackColor);
             SolidBrush lineBrush = new SolidBrush(this.GridColor);
             Pen linePen = new Pen(lineBrush);
             StringFormat foramt = new StringFormat();
             foramt.Alignment = StringAlignment.Center;
             foramt.LineAlignment = StringAlignment.Center;

             Rectangle headRec = new Rectangle(e.CellBounds.Left, lev, ComputeWidth(item.StartX, item.EndX)-1, ComputeHeight(item.StartY, item.EndY)-1);
             e.Graphics.FillRectangle(backgroundBrush, headRec);
             e.Graphics.DrawLine(linePen, headRec.Left, headRec.Bottom, headRec.Right, headRec.Bottom);
             e.Graphics.DrawLine(linePen, headRec.Right, headRec.Top, headRec.Right, headRec.Bottom);
             e.Graphics.DrawString(item.Content, this.ColumnHeadersDefaultCellStyle.Font, Brushes.Black,headRec, foramt);
         }
     }

     public class HeaderItem
     {
         private int _startX;
         private int _startY;
         private int _endX;
         private int _endY;
         private bool _baseHeader;

         public HeaderItem(int startX, int endX, int startY, int endY, string content)
         {
             this._endX = endX;
             this._endY = endY;
             this._startX = startX;
             this._startY = startY;
             this.Content = content;
         }

         public HeaderItem(int x, int y, string content):this(x,x,y,y,content)
         {

         }

         public HeaderItem()
         {

         }

         public static HeaderItem CreateBaseHeader(int x,int y,string content)
         {
             HeaderItem header = new HeaderItem();
             header._endX= header._startX = x;
             header._endY= header._startY = y;
             header._baseHeader = true;
             header.Content = content;
             return header;
         }

         public int StartX
         {
             get { return _startX; }
             set
             {
                 if (value > _endX)
                 {
                     _startX = _endX;
                     return;
                 }
                 if (value < 0) _startX = 0;
                 else _startX = value;
             }
         }

         public int StartY
         {
             get { return _startY; }
             set
             {
                 if (_baseHeader)
                 {
                     _startY = 0;
                     return;
                 }
                 if (value > _endY)
                 {
                     _startY = _endY;
                     return;
                 }
                 if (value < 0) _startY = 0;
                 else _startY = value;
             }
         }

         public int EndX
         {
             get { return _endX; }
             set
             {
                 if (_baseHeader)
                 {
                     _endX = _startX;
                     return;
                 }
                 if (value < _startX)
                 {
                     _endX = _startX;
                     return;
                 }
                 _endX = value;
             }
         }

         public int EndY
         {
             get { return _endY; }
             set
             {
                 if (value < _startY)
                 {
                     _endY = _startY;
                     return;
                 }
                 _endY = value;
             }
         }

         public bool IsBaseHeader
         {get{ return _baseHeader;} }

         public string Content { get; set; }
     }

     public class HeaderCollection
     {
         private List<HeaderItem> _headerList;
         private bool _iniLock;

         public DataGridViewColumnCollection BindCollection{get;set;}

         public HeaderCollection(DataGridViewColumnCollection cols)
         {
             _headerList = new List<HeaderItem>();
             BindCollection=cols;
             _iniLock = false;
         }

         public int GetHeaderLevels()
         {
             int max = 0;
             foreach (HeaderItem item in _headerList)
                 if (item.EndY > max)
                     max = item.EndY;

             return max;
         }

         public List<HeaderItem> GetBaseHeaders()
         {
             List<HeaderItem> list = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.IsBaseHeader) list.Add(item);
             return list;
         }

         public HeaderItem GetHeaderByLocation(int x, int y)
         {
             if (!_iniLock) InitHeader();
             HeaderItem result=null;
             List<HeaderItem> temp = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.StartX <= x && item.EndX >= x)
                     temp.Add(item);
             foreach (HeaderItem item in temp)
                 if (item.StartY <= y && item.EndY >= y)
                     result = item;

             return result;
         }

         public IEnumerator GetHeaderEnumer()
         {
             return _headerList.GetEnumerator();
         }

         public void AddHeader(HeaderItem header)
         {
             this._headerList.Add(header);
         }

         public void AddHeader(int startX, int endX, int startY, int endY, string content)
         {
             this._headerList.Add(new HeaderItem(startX,endX,startY,endY,content));
         }

         public void AddHeader(int x, int y, string content)
         {
             this._headerList.Add(new HeaderItem(x, y, content));
         }

         public void RemoveHeader(HeaderItem header)
         {
             this._headerList.Remove(header);
         }

         public void RemoveHeader(int x, int y)
         {
            HeaderItem header= GetHeaderByLocation(x, y);
            if (header != null) RemoveHeader(header);
         }

         private void InitHeader()
         {
             _iniLock = true;
             for (int i = 0; i < this.BindCollection.Count; i++)
                 if(this.GetHeaderByLocation(i,0)==null)
                 this._headerList.Add(HeaderItem.CreateBaseHeader(i,0 , this.BindCollection[i].HeaderText));
             _iniLock = false;
         }
     }