Code
namespace myControls
{
    // 自定义GridView的Field字段，该字段能够在显示模式下
    // 显示多行文本，在编辑模式下显示多行输入框
    public class LongTextField:  BoundField   // 继承BoundField
    {
        private Unit _width = new Unit("250px");
        private Unit _height = new Unit("60px");
        // LongTextField有两个属性，分别是Widht和Height.
        public Unit Width {
            get { return _width; }
            set { _width = value; }
        }
        public Unit Height {
            get { return _height; }
            set { _height = value; }
        }

// InitializeDataCell 方法是一种帮助器方法，用于初始化 BoundField 对象中的单元格
        // 扩展 BoundField 类时，可以重写该方法，以执行自定义初始化例程。
        protected override void InitializeDataCell(DataControlFieldCell cell, DataControlRowState rowState)
        {
            // 不处于编辑模式下
            if((rowState&DataControlRowState.Edit)==0){
                HtmlGenericControl div = new HtmlGenericControl("div"); //创建一个Html中的div控件
                div.Attributes["class"] = "longTextField"; 
                //通过HtmlTextWriterStyle设置div控件的样式
                div.Style[HtmlTextWriterStyle.Width] = _width.ToString();
                div.Style[HtmlTextWriterStyle.Height] = _height.ToString();
                div.Style[HtmlTextWriterStyle.Overflow] = "auto";
                // div控件的DataBinding事件发生时，调用div_DataBinding函数
                div.DataBinding += new EventHandler(div_DataBinding);
                cell.Controls.Add(div);
            } else {
                TextBox txtEdit = new TextBox();
                txtEdit.TextMode = TextBoxMode.MultiLine;
                txtEdit.Width = _width;
                txtEdit.Height = _height;
                // txtEdit的DataBinding事件发生时，调用txtEdit_DataBinding函数
                txtEdit.DataBinding += new EventHandler(txtEdit_DataBinding);
                cell.Controls.Add(txtEdit);
            }
        }

void div_DataBinding(object sender,EventArgs e)
        {
            HtmlGenericControl div = (HtmlGenericControl)sender;  // 取得控件
            object value = this.GetValue(div.NamingContainer); // Get the field value;
            div.InnerText = this.FormatDataValue(value, this.HtmlEncode); // Assign the formatted value
        }

void txtEdit_DataBinding(object sender,EventArgs e)
        {
            TextBox txtEdit = (TextBox)sender;
            Object value = this.GetValue(txtEdit.NamingContainer); // Get the field value
            txtEdit.Text = this.FormatDataValue(value, this.HtmlEncode);
        }
    }
}

Code
<%@ Register TagPrefix="custom" Namespace="myControls" %>  <!-- 引入LongTextField类型 -->

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"  
           DataKeyNames="Id" DataSourceID="SqlDataSource1">
         <Columns>
                <asp:BoundField DataField="Id" HeaderText="Id" InsertVisible="False"  ReadOnly="True" SortExpression="Id" />
                <asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title" />
                <asp:BoundField DataField="Director" HeaderText="Director"  SortExpression="Director" />
                <custom:LongTextField DataField="Description" Width="300px" height="60px" HeaderText="Movie Description" />
         </Columns>
</asp:GridView>

Code
public class DeleteButtonField : ButtonField
{
    private string _confirmMessage = "确认要删除吗?";

public string ConfirmMessage
    {
        get { return _confirmMessage; }
        set { _confirmMessage = value; }
    }

// 默认情况下，作为删除按钮，按钮上显示删除字样
    public DeleteButtonField()
    {
        this.CommandName = "Delete";
        this.Text = "删除";
    }

public override void InitializeCell(DataControlFieldCell cell, DataControlCellType cellType, DataControlRowState rowState, int rowIndex)
    {
        base.InitializeCell(cell, cellType, rowState, rowIndex);
        if(cellType==DataControlCellType.DataCell) //如果是数据Cell
        {
            WebControl button = (WebControl)cell.Controls[0];
            button.Attributes["onclick"] = String.Format("return confirm('{0}');", _confirmMessage);
        }
    }
}