.Net中使用一般处理程序读取数据库中Image类型(二进制)字段

前台代码:

 

        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
            DataSourceID="SqlDataSource1">
            <Columns>
                <asp:BoundField DataField="EmployeeID" HeaderText="EmployeeID" 
                    InsertVisible="False" ReadOnly="True" SortExpression="EmployeeID" />
                <asp:BoundField DataField="LastName" HeaderText="LastName" 
                    SortExpression="LastName" />
                <asp:TemplateField HeaderText="Photo" SortExpression="Photo">
                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("Photo") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate><!--这里调用一般处理程序!!!注意这里必须使用' '号否则会出错!-->
                       <img src='Handler.ashx?EmployeeId=<%#Eval("EmployeeId") %>' />                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
        <br />
        
    
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
            ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>" 
            SelectCommand="SELECT [EmployeeID], [LastName] FROM [Employees]">
        </asp:SqlDataSource>

 

 注意：如果数据绑定表达式作为属性的值，只要数据绑定表达式中没有出现双引号，那么<%#数据绑定表达式%>的最外层用双引号或者单引号都可以。如果数据绑定表达式中出现双引号，则<%#数据绑定表达式%>的最外层最好要用单引号。

 

 HttpHanlder程序:

 

<%@ WebHandler Language="C#" Class="ImageHandler" %>

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Configuration;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;

public class ImageHandler : IHttpHandler 
{
    //取得数据连接配置
    static ConnectionStringSettings connString = WebConfigurationManager.ConnectionStrings["NorthwindConnectionString"];

    public void ProcessRequest(HttpContext context)
    {
        MemoryStream ms=null;
        try
        {
            //取得员工代号
            string EmployeeID = context.Request.QueryString["EmployeeID"];
            //通过ReadImage类的GetImage()方法取得SQL Server中图片资料
            //建立Sql命令
            string strSQL = "Select Photo from Employees where EmployeeID=@paramEmployeeID";
            //建立SqlDataSource
            SqlDataSource sqldsPhoto = new SqlDataSource(connString.ConnectionString, strSQL);
            sqldsPhoto.SelectParameters.Add("paramEmployeeID", TypeCode.Int32, EmployeeID);
            //通过SqlDataSource进行查詢
            DataView dv = (DataView)sqldsPhoto.Select(DataSourceSelectArguments.Empty);
            //回传DataView第一个Row的Photo字段资料
            if (!(dv[0]["Photo"] is DBNull))
            {//注意:这里需要判断下是否是DBNull否则会报异常,虽然这个例子没有抛出异常.
                Byte[] PhotoImage = (Byte[])dv[0]["Photo"];
                ms = new MemoryStream(PhotoImage, 0, PhotoImage.Length);
            }   
        }
        catch
        {
        }
        
        if (ms != null)
        {
            //取得影像MemoryStream大小
            int bufferSize = (int)ms.Length;
            //建立 buffer
            byte[] buffer = new byte[bufferSize];
            //调用MemoryStream.Read，自MemoryStream 读取至buffer，并传回count
            int countSize = ms.Read(buffer, 0, bufferSize);
            //传回影像buffer
            context.Response.OutputStream.Write(buffer, 0, countSize);
        }
    }
 
    public bool IsReusable 
    {
        get 
        {
            return false;
        }
    }
}