<EditItemTemplate>
                        <asp:FileUpload ID="fuUpload" runat="server" />
                        <asp:Button ID="btnUpdateImage" runat="server" CommandArgument='<%#Eval("CategoryID") %>'
                            CommandName="upload" Text="上传" />
                    </EditItemTemplate>
                    <ItemTemplate>
                        <!--用ajax实现gridview的图片特效-->
                        <img id="image" alt="" runat="server" src='<%# "GetCategoryImage.aspx?ID=" + Eval("CategoryID") %>'
                            height="80" width="70" />
                        <!--<asp:Image ID="Image1" runat="server" Height="90" ImageUrl='<%# "GetCategoryImage.aspx?ID=" + Eval("CategoryID") %>'
                            Width="130" />-->
                    </ItemTemplate>
                    <ItemStyle Height="160px" />
                </asp:TemplateField>

 protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "upload")
        {
            GridViewRow gvr = ((GridViewRow)(((Button)(e.CommandSource)).Parent.Parent));//此得出的值是表示那行被选中的索引值
            int Key = Convert.ToInt32(GridView1.DataKeys[gvr.RowIndex].Value);
            FileUpload fu = (FileUpload)this.GridView1.Rows[gvr.RowIndex].Cells[1].FindControl("fuUpload");
            int updateImagelength = fu.PostedFile.ContentLength;
            byte[] updateimage = new byte[updateImagelength];
            fu.PostedFile.InputStream.Read(updateimage, 0, updateImagelength);
            using (NorthwindEntities ctx = new NorthwindEntities())
            {
                var category = ctx.Categories.First(p => p.CategoryID == Key);
                category.Picture = updateimage;
                ctx.SaveChanges();
            }
        }
    }