Hi ilanocf,

Note: For this sample i have refer below article. For more details refer below article.

Retrieve and display PDF Files from database in browser in ASP.Net

Inside the updatepanel in Triggers you need to use PostBackTrigger and assing id to upload button.

Please refer below samples.

HTML

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="true">
    <ContentTemplate>
        <asp:FileUpload ID="FileUpload1" runat="server" />
        <asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="Upload" />
        <hr />
        <asp:GridView ID="gvFiles" runat="server" AutoGenerateColumns="false">
            <Columns>
                <asp:BoundField DataField="Name" HeaderText="File Name" />
                <asp:TemplateField ItemStyle-HorizontalAlign="Center">
                    <ItemTemplate>
                        <a class="view" href="javascript:;" rel='<%# Eval("Id") %>'>View PDF</a>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
        <hr />
        <div id="pdf_container">
        </div>
    </ContentTemplate>
    <Triggers>
        <asp:PostBackTrigger ControlID="btnUpload" />
    </Triggers>
</asp:UpdatePanel>

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

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.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();
            gvFiles.DataSource = cmd.ExecuteReader();
            gvFiles.DataBind();
            con.Close();
        }
    }
}

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);
}

[System.Web.Services.WebMethod]
public static object GetPDF(int fileId)
{
    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", fileId);
            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();
        }
    }

    return new { FileName = fileName, ContentType = contentType, Data = bytes };
}

VB.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.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()
            gvFiles.DataSource = cmd.ExecuteReader()
            gvFiles.DataBind()
            con.Close()
        End Using
    End Using
End Sub
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(CType(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
    
<System.Web.Services.WebMethod()> _
Public Shared Function GetPDF(ByVal fileId As Integer) As Object
    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", fileId)
            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

    Return New With {.FileName = fileName, .ContentType = contentType, .Data = bytes}
End Function

Screenshot