//换行
DataGrid1.Attributes.Add("style","word-break:keep-all;word-wrap:normal");
当内容为数字 ，则必须
void DataGrid1_DataBound(Object sender, DataGridItemEventArgs e)
{
  if( e.Item.ItemType == ListItemType.Item ||
    e.Item.ItemType == ListItemType.AlternatingItem)
   e.Item.Cells[1].Text = "<nobr>" + e.Item.Cells[1].Text + "</nobr>";
}

或者
private void DataGrid1_ItemCreated(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
  {
   if(e.Item.ItemType ==ListItemType.Header||e.Item .ItemType==ListItemType.Item ||e.Item .ItemType ==ListItemType.AlternatingItem)
   {
    for(int i=0;i<e.Item .Cells .Count ;i++)
    {
     e.Item .Cells [i].Attributes .Add ("nowrap","nowrap");
    }
   }
  }
 
//自动换行
DataGrid1.Attributes.Add("style","word-break:break-all;word-wrap:break-word");