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Webform 文件上传、 C#加图片水印 、 图片验证码
文件上传：
要使用控件 - FileUpload
1、如何判断是否选中文件？
FileUpload.FileName -
选中文件的文件名，如果长度不大于0，那么说明没选中任何文件
js - f.value.length
2、如何保存到服务器上？
FileUpload.SaveAs("绝对路径");
3、如何获得绝对路径？
先编写相对路径 - "UpLoads/abc.txt"
将相对路径映射成绝对路径 - Server.MapPath("UpLoads/abc.txt");
4、现在只能上传成为txt文件，并且名字只能是abc
如何保留文件原有的名字和文件类型？
"UpLoads/" + FileUpload1.FileName;
5、如何防止重名覆盖的问题？
"UpLoads/" + Request.Cookies["user"].Value + DateTime.Now.ToString("yyyyMMddhhmmssms") + FileUpload1.FileName;
6、如何限制选中文件的类型？
限制普通人，给控件添加属性 - accept=".jpg,.png,.jpeg,.txt"
限制找事的：
document.getElementById("Button1").onclick = function () {
var fileName = document.getElementById("FileUpload1").value;
var name = fileName.substr(fileName.length - 4, 4);
var name1 = fileName.substr(fileName.length - 5, 5);
if (name != ".jpg" && name != ".png" && name != ".txt" && name1 != ".jpeg")
{
alert("请选择正确的文件！你要找事儿啊？？");
return false;
}
};
7、控制上传文件的大小
扩容 - 系统默认允许最大上传长度是4MB
webconfig配置文件中写入
<system.web>
<compilation debug="false" targetFramework="4.0" />
<httpRuntime maxRequestLength="40000" />
</system.web>
百度搜，研究，C#大文件上传，断点续传。
注意！不要扩的太多，否则多人同时上传大文件会造成服务器内存不足！
限制大小
C#端限制：
if (FileUpload1.PostedFile.ContentLength>(4*1024*1024))
{
Label1.Text = "文件长度过长！！！";
return;
}
JS端限制：
var f = document.getElementById("FileUpload1");
if (f.files[0].size > (4 * 1024 * 1024)) {
alert("文件过大！！！");
return false;
}
上传图片加水印：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title></title> <style type="text/css"> #Image1 { width: 500px; } </style></head><body> <form id="form1" runat="server"> <div> <asp:FileUpload ID="FileUpload1" runat="server" /> <asp:Button ID="Button1" runat="server" Text="上传" /> <br /> <asp:Image ID="Image1" runat="server" /> </div> </form></body></html>
后台：
using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;public partial class _Default : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { Button1.Click += Button1_Click; } void Button1_Click(object sender, EventArgs e) { System.Drawing.Image img = System.Drawing.Image.FromStream(FileUpload1.FileContent); Graphics g = Graphics.FromImage(img); string s = "汉企奇点网络0928"; Font f = new Font("微软雅黑",20); Brush b = new SolidBrush(Color.Red); PointF p = new PointF(20,20); g.DrawString(s, f, b, p); string sss = "images/"+DateTime.Now.ToString("yyyyMMddhhmmssms")+FileUpload1.FileName; img.Save(Server.MapPath(sss)); Image1.ImageUrl = sss; }}
图片验证码：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title></title></head><body> <form id="form1" runat="server"> <div> <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <asp:Image ID="Image1" runat="server" ImageUrl="YZM.aspx" /> <asp:Button ID="Button1" runat="server" Text="验证" /> <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label> </div> </form></body></html><script type="text/javascript"> var a = 0; document.getElementById("Image1").onclick = function () { this.setAttribute("src", "yzm.aspx?id=" + a); a++; }</script>
后台：
using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;public partial class Default2 : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { Button1.Click += Button1_Click; } void Button1_Click(object sender, EventArgs e) { string t1 = TextBox1.Text; string t2 = Session["YZM"].ToString(); if (t1.ToUpper() == t2.ToUpper()) { Label1.Text = "验证成功！"; } else { Label1.Text = "验证失败！"; } }}
验证码图片：
（前台不用写）
using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;public partial class YZM : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { Bitmap img = new Bitmap(80, 40); Graphics g = Graphics.FromImage(img); Random r = new Random(); //单独加颜色 //List<Color> clist = new List<Color>(); //clist.Add(Color.Yellow); //clist.Add(Color.Green); //clist.Add(Color.Blue); //clist.Add(Color.Pink); //clist.Add(Color.Orange); //clist.Add(Color.Black); //g.FillRectangle(new SolidBrush(clist[r.Next(0, clist.Count)]), 0, 0, 80, 40); //for (int i = 0; i < 10; i++) //{ // Color ccc = clist[r.Next(0, clist.Count)]; // Pen ppp = new Pen(new SolidBrush(ccc), r.Next(1, 5)); // g.DrawLine(ppp, new PointF(r.Next(0, 80), r.Next(0, 40)), new PointF(r.Next(0, 80), r.Next(0, 40))); //} //随机数颜色rgba Color yanse = Color.FromArgb(r.Next(255), r.Next(255), r.Next(255), r.Next(255)); g.FillRectangle(new SolidBrush(yanse), 0, 0, 80, 40); for (int i=0;i<1000;i++) { Color yansel = Color.FromArgb(r.Next(255), r.Next(255), r.Next(255), r.Next(255)); Pen ppp = new Pen(new SolidBrush(yansel), r.Next(1, 5)); g.DrawLine(ppp, new PointF(r.Next(0, 80), r.Next(0, 40)), new PointF(r.Next(0, 80), r.Next(0, 40))); } string all = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; string s = ""; for (int i = 0; i < 4; i++) { int a = r.Next(all.Length); s += all.Substring(a, 1); } Session["YZM"] = s; g.DrawString(s, new Font("微软雅黑", 16), new SolidBrush(Color.Red), new PointF(3, 3)); img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png); Response.End(); }}
Webform 文件上传、 C#加图片水印 、 图片验证码