使用ASP.NET上传图片汇总(二)

来源：互联网发布：免费php分类信息系统编辑：程序博客网时间：2024/05/17 03:20

4 客户端检查上传文件类型(以上传图片为例)

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!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>客户端检查上传文件类型</title>
    <script language="javascript">
    function Check_FileType()
    {
        var str=document.getElementById("FileUpload1").value;
        var pos=str.lastIndexOf(".");
        var lastname=str.substring(pos,str.length);
        if(lastname.toLowerCase()!=".jpg"&&lastname.toLowerCase()!=".gif")
        {
            alert("您上传的文件类型为"+lastname+"，图片必须为.jpg,.gif类型");
            return false;
        }
        else
        {
            return true;
        }        
    }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table>
            <tr>
                <td colspan="2">
                    客户端检查上传文件类型</td>                
            </tr>
            <tr>
                <td style="width: 444px">
                    <asp:FileUpload ID="FileUpload1" runat="server" Width="432px" /></td>
                <td style="width: 80px">
                    <asp:Button ID="bt_upload" runat="server" Text="上传图片" OnClick="bt_upload_Click" OnClientClick="return Check_FileType()" /></td>
            </tr>
            <tr>
                <td colspan="2" style="height: 21px">
                    <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="515px"></asp:Label></td>                
            </tr>
        </table>    
    </div>
    </form>
</body>
</html>

注意：点击上传时先触发客户端事件OnClientClick="return Check_FileType()"

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                //if (!IsAllowedExtension(FileUpload1)) 
                //{ 
                //    this.lb_info.Text = "上传文件格式不正确！"; 
                //} 
                if (IsAllowedExtension(FileUpload1) == true)
                {
                    string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                    string serverpath = Server.MapPath("~/images/") + filename;
                    FileUpload1.PostedFile.SaveAs(serverpath);
                    this.lb_info.Text = "上传成功！";
                }
                else
                {
                    this.lb_info.Text = "请上传图片！";
                }
            }
        }
        catch (Exception ex)
        {
            this.lb_info.Text = "上传发生错误！原因：" + ex.ToString();
        }
    }
    private static bool IsAllowedExtension(FileUpload upfile)
    {
        string strOldFilePath = "";
        string strExtension="";
        string[] arrExtension ={ ".gif", ".jpg", ".bmp", ".png" };
        if (upfile.PostedFile.FileName != string.Empty)
        {
            strOldFilePath = upfile.PostedFile.FileName;//获得文件的完整路径名 
            strExtension = strOldFilePath.Substring(strOldFilePath.LastIndexOf("."));//获得文件的扩展名，如：.jpg 
            for (int i = 0; i < arrExtension.Length; i++)
            {
                if (strExtension.Equals(arrExtension[i]))
                {
                    return true;
                }
            }
        }
        return false;
    }
}

注意：若去掉客户端的脚本和客户端事件OnClientClick="return Check_FileType()"，在后台代码

//if (!IsAllowedExtension(FileUpload1)) 
                //{ 
                //    this.lb_info.Text = "上传文件格式不正确！"; 
                //} 
                if (IsAllowedExtension(FileUpload1) == true)

改为：

if (!IsAllowedExtension(FileUpload1))
                {
                    this.lb_info.Text = "上传文件格式不正确！";
                }
else if (IsAllowedExtension(FileUpload1) == true)

即变成服务器端检查上传文件类型。

5 服务器端检查上传文件的类型（文件内部真正的格式）

<body>
    <form id="form1" runat="server">
    <div>
        <table>
            <tr>
                <td colspan="2">
                    服务器检查上传文件类型</td>                
            </tr>
            <tr>
                <td style="width: 444px">
                    <asp:FileUpload ID="FileUpload1" runat="server" Width="432px" /></td>
                <td style="width: 80px">
                    <asp:Button ID="bt_upload" runat="server" Text="上传图片" OnClick="bt_upload_Click" /></td>
            </tr>
            <tr>
                <td colspan="2" style="height: 21px">
                    <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="515px"></asp:Label></td>                
            </tr>
        </table>    
    </div>
    </form>
</body>

后台代码：

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                if (IsAllowedExtension(FileUpload1) == true)
                {
                    string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                    string serverpath = Server.MapPath("images/") + filename;
                    FileUpload1.PostedFile.SaveAs(serverpath);
                    this.lb_info.Text = "上传成功！";
                }
                else
                {
                    this.lb_info.Text = "请上传图片";
                }
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }
    private static bool IsAllowedExtension(FileUpload upfile)
    {
        FileStream fs = new FileStream(upfile.PostedFile.FileName, FileMode.Open, FileAccess.Read);
        BinaryReader r = new BinaryReader(fs);
        string fileclass = "";
        byte buffer;
        try
        {
            buffer = r.ReadByte();
            fileclass = buffer.ToString();
            buffer = r.ReadByte();
            fileclass += buffer.ToString();
        }
        catch
        { 
            
        }
        r.Close();
        fs.Close();
        if (fileclass == "255216" || fileclass == "7173"||fileclass=="6677"||fileclass=="13780")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar 
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}