Upload and Download multiple files using C# and VB.Net in Windows Application

Hi smile,

Refer below sample.

Database

I have made use of the following table named tblFiles whose schema is defined as follows.

You can download the database table SQL by clicking the download link below.

Download SQL file

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.IO

Code

C#

private void Form1_Load(object sender, EventArgs e)
{
    this.BindDataGridView(); 
    DataGridViewCheckBoxColumn checkBoxColumn = new DataGridViewCheckBoxColumn();
    checkBoxColumn.HeaderText = "";
    checkBoxColumn.Width = 30;
    checkBoxColumn.Name = "checkBoxColumn";
    this.dataGridView1.Columns.Insert(0, checkBoxColumn);         
}

protected void BindDataGridView()
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT ID,Name FROM tblFiles", con))
        {
            cmd.CommandType = CommandType.Text;
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                sda.Fill(dt);
                this.dataGridView1.DataSource = dt;                        
            }
        }
    }

}

private void btnBrowse_Click(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString);
    using (OpenFileDialog openFileDialog = new OpenFileDialog())
    {
        openFileDialog.Multiselect = true;
        if (openFileDialog.ShowDialog() == DialogResult.OK)
        {
            foreach (string fileNames in openFileDialog.FileNames)
            {
                string contentType = "";
                switch (Path.GetExtension(fileNames).ToLower())
                {
                    case ".jpg":
                        contentType = "image/jpeg";
                        break;
                    case ".png":
                        contentType = "image/png";
                        break;
                    case ".gif":
                        contentType = "image/gif";
                        break;
                    case ".bmp":
                        contentType = "image/bmp";
                        break;
                    case ".doc":
                        contentType = "application/msword";
                        break;
                    case ".docx":
                        contentType = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
                        break;
                    case ".xls":
                        contentType = "application/vnd.ms-excel";
                        break;
                    case ".xlsx":
                        contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
                        break;
                    case ".pdf":
                        contentType = "application/pdf";
                        break;
                    case ".ppt":
                        contentType = "application/vnd.ms-powerpoint";
                        break;
                    case ".pptx":
                        contentType = "application/vnd.openxmlformats-officedocument.presentationml.presentation";
                        break;
                }
                byte[] bytes = File.ReadAllBytes(fileNames);
                using (SqlCommand cmd = new SqlCommand("INSERT INTO tblFiles VALUES (@Name,@ContentType,@Data)", con))
                {
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.AddWithValue("@Name", Path.GetFileName(fileNames));
                    cmd.Parameters.AddWithValue("@ContentType", contentType);
                    cmd.Parameters.AddWithValue("@Data", bytes);
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
            }
        }
    }

    this.BindDataGridView();
}

private void btnDownload_Click(object sender, EventArgs e)
{
    using (FolderBrowserDialog folderBrowserDialog = new FolderBrowserDialog())
    {
        if (folderBrowserDialog.ShowDialog() == DialogResult.OK)
        {
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (Convert.ToBoolean(row.Cells["checkBoxColumn"].Value))
                {
                    string id = row.Cells[1].Value.ToString();
                    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString))
                    {
                        using (SqlCommand cmd = new SqlCommand("SELECT Name,Data FROM tblFiles WHERE ID = @Id", con))
                        {
                            cmd.CommandType = CommandType.Text;
                            cmd.Parameters.AddWithValue("@Id", id);
                            con.Open();
                            using (SqlDataReader sdr = cmd.ExecuteReader())
                            {
                                if (sdr.Read())
                                {
                                    byte[] bytes = (byte[])sdr["Data"];
                                    string fileName = sdr["Name"].ToString();
                                    string path = Path.Combine(folderBrowserDialog.SelectedPath, fileName);
                                    File.WriteAllBytes(path, bytes);
                                }
                            }
                            con.Close();
                        }
                    }
                }
            }

            MessageBox.Show("File downloaded in folder " + folderBrowserDialog.SelectedPath);
        }
    }
}

VB.Net

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles Me.Load
    Me.BindDataGridView()
    Dim checkBoxColumn As DataGridViewCheckBoxColumn = New DataGridViewCheckBoxColumn()
    checkBoxColumn.HeaderText = ""
    checkBoxColumn.Width = 30
    checkBoxColumn.Name = "checkBoxColumn"
    Me.dataGridView1.Columns.Insert(0, checkBoxColumn)
End Sub

Protected Sub BindDataGridView()
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("conString").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("SELECT ID,Name FROM tblFiles", con)
            cmd.CommandType = CommandType.Text
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt As DataTable = New DataTable()
                sda.Fill(dt)
                Me.dataGridView1.DataSource = dt
            End Using
        End Using
    End Using
End Sub

Private Sub btnBrowse_Click(sender As System.Object, e As System.EventArgs) Handles btnBrowse.Click
    Dim con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("conString").ConnectionString)
    Using openFileDialog As OpenFileDialog = New OpenFileDialog()
        openFileDialog.Multiselect = True
        If openFileDialog.ShowDialog() = DialogResult.OK Then
            For Each fileNames As String In openFileDialog.FileNames
                Dim contentType As String = ""
                Select Case Path.GetExtension(fileNames).ToLower()
                    Case ".jpg"
                        contentType = "image/jpeg"
                    Case ".png"
                        contentType = "image/png"
                    Case ".gif"
                        contentType = "image/gif"
                    Case ".bmp"
                        contentType = "image/bmp"
                    Case ".doc"
                        contentType = "application/msword"
                    Case ".docx"
                        contentType = "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
                    Case ".xls"
                        contentType = "application/vnd.ms-excel"
                    Case ".xlsx"
                        contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                    Case ".pdf"
                        contentType = "application/pdf"
                    Case ".ppt"
                        contentType = "application/vnd.ms-powerpoint"
                    Case ".pptx"
                        contentType = "application/vnd.openxmlformats-officedocument.presentationml.presentation"
                End Select

                Dim bytes As Byte() = File.ReadAllBytes(fileNames)

                Using cmd As SqlCommand = New SqlCommand("INSERT INTO tblFiles VALUES (@Name,@ContentType,@Data)", con)
                    cmd.CommandType = CommandType.Text
                    cmd.Parameters.AddWithValue("@Name", Path.GetFileName(fileNames))
                    cmd.Parameters.AddWithValue("@ContentType", contentType)
                    cmd.Parameters.AddWithValue("@Data", bytes)
                    con.Open()
                    cmd.ExecuteNonQuery()
                    con.Close()
                End Using
            Next
        End If
    End Using

    Me.BindDataGridView()
End Sub

Private Sub btnDownload_Click(sender As System.Object, e As System.EventArgs) Handles btnDownload.Click
    Using folderBrowserDialog As FolderBrowserDialog = New FolderBrowserDialog()
        If folderBrowserDialog.ShowDialog() = DialogResult.OK Then
            For Each row As DataGridViewRow In dataGridView1.Rows
                If Convert.ToBoolean(row.Cells("checkBoxColumn").Value) Then
                    Dim id As String = row.Cells(1).Value.ToString()
                    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("conString").ConnectionString)
                        Using cmd As SqlCommand = New SqlCommand("SELECT Name,Data FROM tblFiles WHERE ID = @Id", con)
                            cmd.CommandType = CommandType.Text
                            cmd.Parameters.AddWithValue("@Id", id)
                            con.Open()
                            Using sdr As SqlDataReader = cmd.ExecuteReader()
                                If sdr.Read() Then
                                    Dim bytes As Byte() = CType(sdr("Data"), Byte())
                                    Dim fileName As String = sdr("Name").ToString()
                                    Dim path As String = System.IO.Path.Combine(folderBrowserDialog.SelectedPath, fileName)
                                    File.WriteAllBytes(path, bytes)
                                End If
                            End Using

                            con.Close()
                        End Using
                    End Using
                End If
            Next
        End If

        MessageBox.Show("File downloaded in folder " + folderBrowserDialog.SelectedPath)
    End Using
End Sub

Screenshots

Record In Database

For list of MIME types refer below link.

Complete list of MIME types