鼠标移动到dataGrid单元格，类容全部显示

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

namespace Common
...{
    public class ShowAllColumnText
    ...{
        private System.Windows.Forms.DataGrid dg=null;
        public ShowAllColumnText(System.Windows.Forms.DataGrid dataGrid)
        ...{
            dg=dataGrid;
        }
        ...#region 
        bool showAll=true;
        public void MyMouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
        ...{
            if(showAll)
            ...{
                Graphics gg=this.dg.CreateGraphics();
                TextBox t=(TextBox)sender;
                int w=t.Size.Width;
                Point p=new Point(t.Location.X,e.Y+t.Location.Y+t.Height);
                DrawAllText(((TextBox)sender).Text,w,gg,dg.Font,p);
                showAll=false;
            }

        }
        public void MyMouseLeave(object sender, System.EventArgs e)
        ...{
            showAll=true;
            dg.Refresh();
        }
        
        private void DrawAllText(string text,int w,Graphics g,Font f,Point p)
        ...{
            float h=f.GetHeight();
            SizeF sf=g.MeasureString(text,f,w);
            int height=(int)sf.Height+5+(int)h;
            Size rsf=new Size(w,height);
            Rectangle rect= new Rectangle(p,rsf);
            RectangleF rectf= new RectangleF(new PointF(p.X,p.Y),new SizeF(rsf.Width,rsf.Height));
            
            g.FillRectangle(Brushes.Gray,rect);
            g.DrawRectangle(new Pen(Color.Blue),rect);
            rectf= new RectangleF(new PointF(p.X+3,p.Y+3),new SizeF(sf.Width,sf.Height+(int)h));

            g.DrawString("  "+text,f,Brushes.Blue,rectf);


        }
        #endregion
    }
}