1.这段代码是处理过长字符串的主体；
void ItemDataBound(object sender, DataGridItemEventArgs e)
{
   // Get the string to be displayed
   string title = GetTheString();

   // Returns the updated text for the specified column
   string newText = AdjustTextForDisplay(title, 1, grid);
 
   // Set the text including the tooltip when necessary
   e.Item.Cells[1].Text = newText;
}

2.AdjustTextForDisplay(string,int,DataGrid)函数的功能是根据列的宽度，截取过长的字符串；
这里需要注意的是DataGrid的Font和Columns[colIndex].ItemStyle.Width属性必需有赋值。如果没有赋值的话，函数将会采用系统默认的值。如不加处理，函数会出异常。
string AdjustTextForDisplay(string text, int colIndex, DataGrid grid)
{
   // Calculate the dimensions of the text with the current font
   SizeF textSize = MeasureString(text, grid.Font);
 
   // Compare the size with the column's width
   int colWidth = (int) grid.Columns[colIndex].ItemStyle.Width.Value;
   if(textSize.Width > colWidth)
   {
      // Get the exceeding pixels
      int delta = (int) (textSize.Width - colWidth);
 
      // Calculate the average width of the characters (apPRox)
      int avgCharWidth = (int) (textSize.Width/text.Length);
 
      // Calculate the number of chars to trim to stay in the fixed width (approx)
      int chrToTrim = (int) (delta/avgCharWidth);
 
      // Get the proper substring + the ellipsis
      // Trim 2 more chars (approx) to make room for the ellipsis
      string rawText = text.Substring(0, text.Length-(chrToTrim+2)) + "";
 
      // Format to add a tooltip
      string fmt = "{1}";
      return String.Format(fmt, text, rawText);
   }
   return text;
}