c#图片上传和显示的实现方法

由于需要图片上传的功能，所以花了一些时间网上找相关资料终于搞定，效果图如下：

下面的是解决方案截图和上传的图片截图：

具体实现代码如下：

1.界面代码

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="UploadPic.aspx.cs" Inherits="Pic_Try.UploadPic" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>图片上传和显示</title>
  <style type="text/css">
  .pic_text{ color:Red;}
  .pic_label { color:Gray; margin-top:5px; margin-bottom:5px;}
  .pic_image { margin:5px;}
  </style>
</head>
<body>
  <form id="form1" runat="server">
  <div class="pic_image"><asp:Image ID="pic" runat="server" /></div>
  <div><asp:FileUpload ID="pic_upload" runat="server" /><asp:Label ID="lbl_pic" runat="server" class="pic_text"></asp:Label></div>
  <div class="pic_label">上传图片格式为.jpg, .gif, .bmp,.png,图片大小不得超过8M</div>
  <div><asp:Button ID="btn_upload" runat="server" Text="上传" onclick="btn_upload_Click"/></div>
  </form>

</body>
</html>

2.后台代码UploadPic.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Security.Cryptography;
using System.Web.Security;

namespace Pic_Try
{
  public partial class UploadPic : System.Web.UI.Page
  {
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btn_upload_Click(object sender, EventArgs e)
    {
      Boolean fileOk = false;
      if (pic_upload.HasFile)//验证是否包含文件
      {
        //取得文件的扩展名,并转换成小写
        string fileExtension = Path.GetExtension(pic_upload.FileName).ToLower();
        //验证上传文件是否图片格式
        fileOk = IsImage(fileExtension);

        if (fileOk)
        {
          //对上传文件的大小进行检测，限定文件最大不超过8M
          if (pic_upload.PostedFile.ContentLength < 8192000)
          {
            string filepath = "/images/";
            if (Directory.Exists(Server.MapPath(filepath)) == false)//如果不存在就创建file文件夹
            {
              Directory.CreateDirectory(Server.MapPath(filepath));
            }
            string virpath = filepath + CreatePasswordHash(pic_upload.FileName, 4) + fileExtension;//这是存到服务器上的虚拟路径
            string mappath = Server.MapPath(virpath);//转换成服务器上的物理路径
            pic_upload.PostedFile.SaveAs(mappath);//保存图片
            //显示图片
            pic.ImageUrl = virpath;
            //清空提示
            lbl_pic.Text = "";
          }
          else {
            pic.ImageUrl = "";
            lbl_pic.Text = "文件大小超出8M！请重新选择！";
          }
        }
        else {
          pic.ImageUrl = "";
          lbl_pic.Text = "要上传的文件类型不对！请重新选择！";
        }
      }
      else
      {
        pic.ImageUrl = "";
        lbl_pic.Text = "请选择要上传的图片！";
      }
    }

    /// <summary>
    /// 验证是否指定的图片格式
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public bool IsImage(string str) {
      bool isimage = false;
      string thestr = str.ToLower();
      //限定只能上传jpg和gif图片
      string[] allowExtension = { ".jpg", ".gif", ".bmp",".png" };
      //对上传的文件的类型进行一个个匹对
      for (int i = 0; i < allowExtension.Length; i++)
      {
        if (thestr == allowExtension[i])
        {
          isimage = true;
          break;
        }
      }
      return isimage;
    }

    /// <summary>
    /// 创建一个指定长度的随机salt值
    /// </summary>
    public string CreateSalt(int saltLenght)
    {
      //生成一个加密的随机数
      RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
      byte[] buff = new byte[saltLenght];
      rng.GetBytes(buff);
      //返回一个Base64随机数的字符串
      return Convert.ToBase64String(buff);
    }

    /// <summary>
    /// 返回加密后的字符串
    /// </summary>
    public string CreatePasswordHash(string pwd, int saltLenght)
    {
      string strSalt = CreateSalt(saltLenght);
      //把密码和Salt连起来
      string saltAndPwd = String.Concat(pwd, strSalt);
      //对密码进行哈希
      string hashenPwd = FormsAuthentication.HashPasswordForStoringInConfigFile(saltAndPwd, "sha1");
      //转为小写字符并截取前16个字符串
      hashenPwd = hashenPwd.ToLower().Substring(0, 16);
      //返回哈希后的值
      return hashenPwd;
    }
  }
}

3.最后防止上传大文件图片时报错，配置文件添加配置Web.config

<?xml version="1.0" encoding="utf-8"?>

<!--
 有关如何配置 ASP.NET 应用程序的详细消息，请访问
 http://go.microsoft.com/fwlink/?LinkId=169433
 -->

<configuration>
  <system.web>
   <compilation debug="true" targetFramework="4.0" />
   <httpRuntime executionTimeout="240" maxRequestLength="8192000"/>
  </system.web>

</configuration>

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