FileUpload 简单上传+小预览

页面代码 :

    <form id="form1" runat="server">
    <div>
        <asp:FileUpload ID="FileUpload1" runat="server" />
        <asp:Button ID="Button1" runat="server" Text="上传" Width="54px"  OnClick="Button1_Click" />
        <asp:Label ID="Label1" runat="server" Text="" Style="color: Red"></asp:Label>
       <asp:Image runat="server" ID="Image1" Style="z-index: 102; left: 20px; position: absolute;
           top: 49px" Width="73px" />
    </div>
    </form>

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;

namespace Web.File
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
        #region 文件上传
        /// <summary>
        /// 文件上传
        /// </summary>
        protected void Button1_Click(object sender, EventArgs e)
        {
            if (FileUpload1.FileName == "")
            {
                this.Label1.Text = "上传文件不能为空";
                return;
            }

            bool fileIsValid = false;
            //如果确认了上传文件，则判断文件类型是否符合要求
            if (this.FileUpload1.HasFile)
            {
                //获取上传文件的后缀
                String fileExtension = System.IO.Path.GetExtension(this.FileUpload1.FileName).ToLower();
                String[] restrictExtension = { ".gif", ".jpg", ".bmp", ".png" };
                //判断文件类型是否符合要求
                for (int i = 0; i < restrictExtension.Length; i++)
                {
                    if (fileExtension == restrictExtension[i])
                    {
                        fileIsValid = true;
                    }
                    //如果文件类型符合要求,调用SaveAs方法实现上传,并显示相关信息
                    if (fileIsValid == true)
                    {
                        //上传文件是否大于10M
                        if (FileUpload1.PostedFile.ContentLength > (10 * 1024 * 1024))
                        {
                            this.Label1.Text = "上传文件过大";
                            return;
                        }
                        try
                        {
                            this.Image1.ImageUrl = "~/File/" + FileUpload1.FileName;
                            this.FileUpload1.SaveAs(Server.MapPath("~/File/") + FileUpload1.FileName);
                            this.Label1.Text = "文件上传成功!";
                        }
                        catch
                        {
                            this.Label1.Text = "文件上传失败！";
                        }
                        finally
                        {

                        }
                    }
                    else
                    {
                        this.Label1.Text = "只能够上传后缀为.gif,.jpg,.bmp,.png的文件";
                    }
                }
            }
        }
        #endregion
    }
}

Web.config 配置:

<!--因为FileUpload 控件上传最大为4M,如果要上传更大文件,改下maxRequestLength的大小-->
<configuration>
    <system.web>
        <compilation debug="true" targetFramework="4.0" />
      <httpRuntime  requestValidationMode="2.0" maxRequestLength="10485760" executionTimeout="3600" appRequestQueueLimit="10000"/>
    </system.web>
</configuration>

效果:存在浏览器兼容问题

小白正学习中......