<asp:GridView ID="GridView1" runat="server" 
    DataKeyNames="PhotoID" 
    AllowPaging="True" 
    AutoGenerateColumns="False" 
    OnRowDeleting="GridView1_RowDeleting" 
    OnRowDataBound="GridView1_RowDataBound" 
    OnPageIndexChanging="GridView1_PageIndexChanging">
            <Columns>
<asp:ImageField DataImageUrlField="PhotoPath" HeaderText="缩略图">
            </Columns>
     </asp:GridView>

        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                Image x = e.Row.Cells[2].Controls[0] as Image;
                SetimageSize(x, 20);


                //高亮显示指定行
                e.Row.Attributes.Add("onMouseOver", "Color=this.style.backgroundColor;this.style.backgroundColor='#336699';C=this.style.Color;this.style.Color='#ff0000'");
                e.Row.Attributes.Add("onMouseOut", "this.style.backgroundColor=Color;");
                //e.Row.Attributes.Add("onMouseOver", "C=this.style.Color;this.style.Color='#336699'");
                //e.Row.Attributes.Add("onMouseOver", "Color=this.style.fontColor;this.style.fontColor='#000000'");
                //删除指定行数据时，弹出询问对话框
                ((LinkButton)(e.Row.Cells[3].Controls[0])).Attributes.Add("onclick", "return confirm('是否删除当前行数据！')");
            }
        }

        public void SetimageSize(System.Web.UI.WebControls.Image Image, int MaxW)
        {
            SqlDataAdapter da = new SqlDataAdapter("select * from Photo where PhotoUser ='" + Session["UserName"].ToString() + "' order by PhotoID desc", cn);
            DataSet ds = new DataSet();
            da.Fill(ds);
            string photoPath = ds.Tables[0].Rows[0][3].ToString();

               //System.IO.File.Exists
            if (!File.Exists(Server.MapPath(photoPath)))
            {
            
            }
            else
            {
                System.Drawing.Image img = System.Drawing.Image.FromFile(Server.MapPath(photoPath));
                if (img.Width > MaxW)
                {
                    int Nw = Convert.ToInt32((float)img.Width - ((float)img.Width - (float)150));
                    int Nh = Convert.ToInt32((float)img.Height / ((float)img.Width / (float)Nw));
                    Image.Width = Nw;
                }
            }
            //System.Drawing.Image img = System.Drawing.Image.FromFile(Page.Server.MapPath(Image.Src.Replace("..", "")));
        }