In this article I will explain with an example, how to read and write BLOBs (Binary Large Objects) data to SQL Server database using C# and VB.Net.
BLOBs include files such as Images, PDF, Word or Excel Documents, Audio, Video files. Such files are read and converted to an array of bytes and inserted into SQL Server VARBINARY or IMAGE fields.
Database
This article makes use of a table named tblFiles whose schema is defined as follows.
![Read and Write BLOB Data to SQL Server database using C# and VB.Net]()
Note: You can download the database table SQL by clicking the download link below.
Download SQL file
HTML Markup
The HTML Markup contains a FileUpload and Button to upload and save the files to database and an ASP.Net GridView control to display the uploaded files and also to allow the user to download the file saved in database. The ID of the File is bound to the CommandArgument property of the LinkButton. It will later be used to download the file.
<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="Upload" />
<hr />
<asp:GridView ID="GridView1" runat="server" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
RowStyle-BackColor="#A1DCF2" AlternatingRowStyle-BackColor="White" AlternatingRowStyle-ForeColor="#000"
AutoGenerateColumns="false">
<Columns>
<asp:BoundField DataField="Name" HeaderText="File Name"/>
<asp:TemplateField ItemStyle-HorizontalAlign = "Center">
<ItemTemplate>
<asp:LinkButton ID="lnkDownload" runat="server" Text="Download" OnClick="DownloadFile"
CommandArgument='<%# Eval("Id") %>'></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Namespaces
You will need to import the following namespaces.
C#
using System.IO;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
VB.Net
Imports System.IO
Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
Uploading the files and then saving in SQL Server Database table
The below event handler gets executed when the Upload Button is clicked, it simply saves the file as Binary data in the SQL Server Database.
The name of the file, the content type (MIME type) and the actual file as array of bytes are inserted into the database table.
Note: The Content type (MIME type) is very important while downloading the files as it notifies the browser about type of the File.
C#
protected void Upload(object sender, EventArgs e)
{
string filename = Path.GetFileName(FileUpload1.PostedFile.FileName);
string contentType = FileUpload1.PostedFile.ContentType;
using (Stream fs = FileUpload1.PostedFile.InputStream)
{
using (BinaryReader br = new BinaryReader(fs))
{
byte[] bytes = br.ReadBytes((Int32)fs.Length);
string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
string query = "insert into tblFiles values (@Name, @ContentType, @Data)";
using (SqlCommand cmd = new SqlCommand(query))
{
cmd.Connection = con;
cmd.Parameters.AddWithValue("@Name", filename);
cmd.Parameters.AddWithValue("@ContentType", contentType);
cmd.Parameters.AddWithValue("@Data", bytes);
con.Open();
cmd.ExecuteNonQuery();
con.Close();
}
}
}
}
Response.Redirect(Request.Url.AbsoluteUri);
}
VB.Net
Protected Sub Upload(sender As Object, e As EventArgs)
Dim filename As String = Path.GetFileName(FileUpload1.PostedFile.FileName)
Dim contentType As String = FileUpload1.PostedFile.ContentType
Using fs As Stream = FileUpload1.PostedFile.InputStream
Using br As New BinaryReader(fs)
Dim bytes As Byte() = br.ReadBytes(DirectCast(fs.Length, Long))
Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
Using con As New SqlConnection(constr)
Dim query As String = "insert into tblFiles values (@Name, @ContentType, @Data)"
Using cmd As New SqlCommand(query)
cmd.Connection = con
cmd.Parameters.Add("@Name", SqlDbType.VarChar).Value = filename
cmd.Parameters.Add("@ContentType", SqlDbType.VarChar).Value = contentType
cmd.Parameters.Add("@Data", SqlDbType.Binary).Value = bytes
con.Open()
cmd.ExecuteNonQuery()
con.Close()
End Using
End Using
End Using
End Using
Response.Redirect(Request.Url.AbsoluteUri)
End Sub
Reading the uploaded files from Database Table in ASP.Net GridView
Below is the code which populates the ASP.Net GridView from files saved in the database table.
C#
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 tblFiles";
cmd.Connection = con;
con.Open();
GridView1.DataSource = cmd.ExecuteReader();
GridView1.DataBind();
con.Close();
}
}
}
VB.Net
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
If Not IsPostBack Then
BindGrid()
End If
End Sub
Private Sub BindGrid()
Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
Using con As New SqlConnection(constr)
Using cmd As New SqlCommand()
cmd.CommandText = "select Id, Name from tblFiles"
cmd.Connection = con
con.Open()
GridView1.DataSource = cmd.ExecuteReader()
GridView1.DataBind()
con.Close()
End Using
End Using
End Sub
Downloading particular file from Database Table using the Download Button in GridView
The below event handler is raised when the Download LinkButton is clicked inside the GridView Row. Firstly the ID of the File is determined using the CommandArgument property of the LinkButton and then the File data, i.e. Name, Content Type and the Byte Array is fetched from the database.
Once the data fetching process is completed the file is sent to the browser for downloading using the Response Stream.
C#
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 tblFiles 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();
}
VB.Net
Protected Sub DownloadFile(sender As Object, e As EventArgs)
Dim id As Integer = Integer.Parse(TryCast(sender, LinkButton).CommandArgument)
Dim bytes As Byte()
Dim fileName As String, contentType As String
Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
Using con As New SqlConnection(constr)
Using cmd As New SqlCommand()
cmd.CommandText = "select Name, Data, ContentType from tblFiles where Id=@Id"
cmd.Parameters.AddWithValue("@Id", id)
cmd.Connection = con
con.Open()
Using sdr As SqlDataReader = cmd.ExecuteReader()
sdr.Read()
bytes = DirectCast(sdr("Data"), Byte())
contentType = sdr("ContentType").ToString()
fileName = sdr("Name").ToString()
End Using
con.Close()
End Using
End Using
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()
End Sub
Screenshot
![Read and Write BLOB Data to SQL Server database using C# and VB.Net]()
Downloads
