Question

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


public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindGrid();
        }
    }
    private void BindGrid()
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "select id, Name from FileControl";
                cmd.Connection = con;
                con.Open();
                GridView1.DataSource = cmd.ExecuteReader();
                GridView1.DataBind();
                con.Close();
            }
        }
    }
    protected void DownloadFile(object sender, EventArgs e)
    {
        int id = int.Parse((sender as LinkButton).CommandArgument);
        byte[] bytes;
        string fileName, contentType;
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "select Name, Data, ContentType from FileControl where id=@id";
                cmd.Parameters.AddWithValue("@id", id);
                cmd.Connection = con;
                con.Open();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    sdr.Read();
                    bytes = (byte[])sdr["Data"];
                    contentType = sdr["ContentType"].ToString();
                    fileName = sdr["Name"].ToString();
                }
                con.Close();
            }
        }
        Response.Clear();
        Response.Buffer = true;
        Response.Charset = "";
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.ContentType = contentType;
        Response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName);
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();
    }
    protected void View(object sender, EventArgs e)
    {
        int id = int.Parse((sender as LinkButton).CommandArgument);
        string embed = "<object data=\"{0}{1}\" type=\"image/jpg\" width=\"500px\" height=\"300px\">";
        embed += "If you are unable to view file, you can download from <a href = \"{0}{1}&download=1\">here</a>";
        embed += " or download <a target = \"_blank\" href = \"http://get.adobe.com/reader/\">Adobe PDF Reader</a> to view the file.";
        embed += "</object>";
        ltEmbed.Text = string.Format(embed, ResolveUrl("~/FileCS.ashx?Id="), id);
    }
    protected void DeleteFile(object sender, EventArgs e)
    {
        int id = int.Parse((sender as LinkButton).CommandArgument);
        byte[] bytes;
        string fileName, contentType;
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "Delete Name, Data, ContentType from FileControl where id=@id";
                cmd.Parameters.AddWithValue("@id", id);
                cmd.Connection = con;
                con.Open();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    sdr.Read();
                    bytes = (byte[])sdr["Data"];
                    contentType = sdr["ContentType"].ToString();
                    fileName = sdr["Name"].ToString();
                }

                con.Close();
            }

        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Redirect("~/ProfileChange.aspx");
    }
}

这里的视图和下载功能完美无缺。我需要删除上传的文件。问题是我没有使用任何文件夹来存储文件 - 我直接使用数据库来存储文件的路径。请帮我纠正删除功能。

Answer 1

DeleteFile方法具有正确的SQL命令，可以通过id从表FileControl中删除记录。

DeleteFile方法的问题在于它被复制，粘贴并重命名为方法DownloadFile的版本，而DownloadFile有一个返回数据的SQL查询，因此它可以转换FileBlob或将列FileControl.Data更改为具有以下代码的文件：

using (SqlDataReader sdr = cmd.ExecuteReader())
            {
                sdr.Read();
                bytes = (byte[])sdr["Data"];
                contentType = sdr["ContentType"].ToString();
                fileName = sdr["Name"].ToString();
            }

DeleteFile中的代码相同，但SQL语句不会返回数据，而是删除DeleteFile中的记录，需要在DeleteFile中使用ExecuteNonQuery()修复此代码@ErikPhilips在评论中说明

删除C＃数据库中的上传文件

1 个答案: