how do I retrieve multiple images from the databas

问题:

I have a database of 9 images, which keep changing, so I cannot directly set the src in html <img> tag to display the 9 images, I have to pick them from the database and bind them accordingly.

I'm able to retrieve and print 1 image using Response.BinaryWrite(), but not all 9. My byte[] gets only the 1st image from the db,

here's the code,

            while (dr.Read())
            {
                Response.ContentType = "image/jpg";
                Response.BinaryWrite((byte[])(dr["fsImage"]));

            }

How do I retrieve all 9 images, and how do I bind them to either <asp:Image> tag or construct an html <img> tag dynamically

I'm a novice, so please take it easy on me, if there are stupid mistakes ;)

Thanks in advance.

回答1:

You can't have the web page give the content of all the images.

In order to "dynamically" render the image you need to make a page which will give you a single image. This page would use code like what you have above.

Then to pick which image to show the url to the page would change for example

http://youdomain/makeimage.aspx?imageid=1

and

http://youdomain/makeimage.aspx?imageid=2

The code in make image would then return the single image.

A note -- you will be much happier if you make the url

http://youdomain/makeimage.aspx?imageid=1&mytype=.jpg

Thus having the image url end in the extension. Some browsers (IE) cheat and look at the end of the string to see what content type to expect. They will work with a url like above but not without the trialling .jpg.

Also, you will need to implement some form of caching our your performance will be a dog (esp if you try to scale.)

Good luck.

回答2:

Use HttpHandler and call in Img tag

one example

<%@ WebHandler Language="C#" Class="Handler2" %>

using System;
using System.Web;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;


public class Handler2 : IHttpHandler {


    public void ProcessRequest(HttpContext context)
    {

        if (context.Request.QueryString["pid"] != null)
        {
            string ID = context.Request.QueryString["pid"].ToString();

            if (dt.Rows.Count > 0)
            {
                int pid = Convert.ToInt32(ID);
                SqlConnection myConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);
                myConnection.Open();
                //int i = Convert.ToInt32(context.Request.QueryString["id"]);
                string sql = "Select BackGroundImage from Wall_BackgrndImg_Master where FK_Company_Master=@ImageId";
                SqlCommand cmd = new SqlCommand(sql, myConnection);
                cmd.Parameters.Add("@ImageId", SqlDbType.Int).Value = pid;
                cmd.Prepare();
                SqlDataReader dr = cmd.ExecuteReader();
                dr.Read();
                try
                {
                    context.Response.ContentType = "jpg";
                    context.Response.BinaryWrite((byte[])dr["BackGroundImage"]);
                    dr.Close();
                    myConnection.Close();
                }
                catch
                {

                }
            }
        }

    }

    public bool IsReusable {
        get {
            return false;
        }
    }

}

and call like

    <img src="~/handlor.ashx?pid=1">
<img src="~/handlor.ashx?pid=2">
<img src="~/handlor.ashx?pid=3">
<img src="~/handlor.ashx?pid=4">
<img src="~/handlor.ashx?pid=5">