从C＃应用程序上载和下载SQL Server上的文件

Question

I have a C# application that is uploading files to a sql server, I use this code to get the pdf file and then I change it to "bytes" for upload on the SQL Server database.

private void mButtonAddCV_Click(object sender, EventArgs e)
{
    openFileDialog1.Filter = "PDF Files | *.pdf";
    if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
    {
        if (openFileDialog1.FileName.Length > 0)
        {
            pathCV = openFileDialog1.FileName;
        }
    }

    // Read the file and convert it to Byte Array
    string filePath = pathCV;
    string contenttype = String.Empty;

    contenttype = "application/pdf";

    if (contenttype != String.Empty)
    {
        Stream fs = File.OpenRead(filePath);
        BinaryReader br = new BinaryReader(fs);
        bytes = br.ReadBytes((Int32)fs.Length);
    }
}

I use the code below to upload the file:

if (!mConnector.Update("INSERT INTO **** (***, ***, CV) " +
                            "VALUES ('" + *** + "', '" + *** + "', '" + bytes + "')"))
{
    Messages.errorMessageBox("This CV already exists.");
}
else
{
    ChangeScreen(ActiveScreen, ActiveScreens.ActiveScreen_CVList);
}

But now I don't know how to download this file and how to make a pdf file with the data stored on the database to see it. Can anyone help me?

Thanks!

Answer 1

First off, let's change the way you are forming your insert statement so you aren't opening up your system to sql injection. This will also make the insert statement easier to work with

var command = new SqlCommand("INSERT INTO myTable (x, y, z) VALUES (@a, @b, @c)", sqlConnection);
command.Parameters.Add(new SqlParameter("@a", bytes));
command.Parameters.Add(new SqlParameter("@b", bValue));
command.Parameters.Add(new SqlParameter("@c", bValue));

var resultingRows = command.ExecuteNonQuery();

To read the data out, use ExecuteReader, then the File object to save it to the disk.

var command = new SqlCommand("Select a from myTable", sqlConnection);
var reader = command.ExecuteReader();
reader.Read();
var pdfBinaryBuffer = (byte[])reader[0];

// Save file to disk
var file = File.Create("myFile.pdf", pdfBinaryBuffer.Length);
file.Write(pdfBinaryBuffer, 0, pdfBinaryBuffer.Length);
file.Close();

Answer 2

I suggest you to insert your byte data using SqlParameters... see Inserting a byte array into sql server

Then, read the record using SqlDataReader's GetBytes(...) function see here .

Answer 3

I suggest you to upload pdf and save it in separate folder. you can save the path in database table that I think it is good.

Here is code for file upload

Drag “Fileupload” control to .aspx page (Use this code is for save .PDF to folder)

protected void fileUpload()
{
 if (fileUp.HasFile)
            {

                fileUp.SaveAs(Server.MapPath("~/PoPDF/" + this.txtCusPo.Text +".PDF"));
                string imgPrintPo = this.txtCusPo.Text + ".PDF";

            }
}

Here is code for file download

You can put this code in button event but here I have used GridView row command event.

protected void gridview_RowCommand(object sender, GridViewCommandEventArgs e)
{
   GridViewRow row = (GridViewRow)(((LinkButton)e.CommandSource).NamingContainer);
   if (e.CommandName == "SelectDownload")
   {

      Response.Clear();
      Response.ContentType = "application/octet-stream";
      Response.AppendHeader("Content-Disposition", "filename=" + e.CommandArgument);
      Response.TransmitFile(Server.MapPath("~/PoPDF/") + e.CommandArgument);
        //Response.Flush();
             Response.End();
   }

}