Hi kankon,

Using the below article i have created the example.

Check this example. Now please take its reference and correct your code.

Here i have used inline query. You need to replace with Stored Procedure and pass the parameters as per your table structure.

Download (Save) VARBINARY Data as File in ASP.Net using C# and VB.Net

HTML

<asp:GridView runat="server" ID="gvFiles" AutoGenerateColumns="false" AutoGenerateDeleteButton="true"
    AutoGenerateEditButton="true" OnRowCancelingEdit="OnRowCancelingEdit" OnRowDeleting="OnRowDeleting"
    OnRowEditing="OnRowEditing" OnRowUpdating="OnRowUpdating">
    <Columns>
        <asp:BoundField DataField="Name" HeaderText="File Name"></asp:BoundField>
        <asp:TemplateField HeaderText="Files">
            <ItemTemplate>
                <asp:LinkButton ID="lnkDownload" runat="server" Text="Download" OnClick="DownloadFile"
                    CommandArgument='<%# Eval("Id") %>'></asp:LinkButton>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:FileUpload ID="fuFile" runat="server" />
            </EditItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

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#

string str = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        BindGridView();
    }
}

protected void OnRowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
    gvFiles.EditIndex = -1;
    BindGridView();
}

protected void OnRowEditing(object sender, GridViewEditEventArgs e)
{
    gvFiles.EditIndex = e.NewEditIndex;
    BindGridView();
}

protected void OnRowDeleting(object sender, GridViewDeleteEventArgs e)
{
    BindGridView();
}

protected void OnRowUpdating(object sender, GridViewUpdateEventArgs e)
{
    GridViewRow row = gvFiles.Rows[e.RowIndex];
    int id = Convert.ToInt32(gvFiles.DataKeys[e.RowIndex].Values[0]);
    string fileName = (row.Cells[1].Controls[0] as TextBox).Text;
    FileUpload FileUpload1 = row.FindControl("fuFile") as FileUpload;
    string contentType = "";
    byte[] bytes = null;
    if (FileUpload1.HasFile)
    {
        contentType = FileUpload1.PostedFile.ContentType;
        using (Stream fs = FileUpload1.PostedFile.InputStream)
        {
            using (BinaryReader br = new BinaryReader(fs))
            {
                bytes = br.ReadBytes((Int32)fs.Length);
            }
        }
    }

    using (SqlConnection con = new SqlConnection(str))
    {
        string query = "UPDATE tblFiles SET Name = @Name,ContentType = @ContentType,Data=@Data WHERE id = @Id";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@Id", id);
            cmd.Parameters.AddWithValue("@Name", fileName);
            cmd.Parameters.AddWithValue("@ContentType", contentType);
            cmd.Parameters.AddWithValue("@Data", bytes == null ? new byte[] { } : bytes);
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
        }
    }

    gvFiles.EditIndex = -1;
    BindGridView();
}

protected void DownloadFile(object sender, EventArgs e)
{
    int id = int.Parse((sender as LinkButton).CommandArgument);
    byte[] bytes;
    string fileName, contentType;
    using (SqlConnection con = new SqlConnection(str))
    {
        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();
}

private void BindGridView()
{
    using (SqlConnection con = new SqlConnection(str))
    {
        using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM tblFiles", con))
        {
            using (DataTable dt = new DataTable())
            {
                da.Fill(dt);
                gvFiles.DataSource = dt;
                gvFiles.DataBind();
            }
        }
    }
}

VB.Net

Private str As String = ConfigurationManager.ConnectionStrings("conString").ConnectionString
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        BindGridView()
    End If
End Sub

Protected Sub OnRowCancelingEdit(ByVal sender As Object, ByVal e As GridViewCancelEditEventArgs)
    gvFiles.EditIndex = -1
    BindGridView()
End Sub

Protected Sub OnRowEditing(ByVal sender As Object, ByVal e As GridViewEditEventArgs)
    gvFiles.EditIndex = e.NewEditIndex
    BindGridView()
End Sub

Protected Sub OnRowDeleting(ByVal sender As Object, ByVal e As GridViewDeleteEventArgs)
    BindGridView()
End Sub

Protected Sub OnRowUpdating(ByVal sender As Object, ByVal e As GridViewUpdateEventArgs)
    Dim row As GridViewRow = gvFiles.Rows(e.RowIndex)
    Dim id As Integer = Convert.ToInt32(gvFiles.DataKeys(e.RowIndex).Values(0))
    Dim fileName As String = (TryCast(row.Cells(1).Controls(0), TextBox)).Text
    Dim FileUpload1 As FileUpload = TryCast(row.FindControl("fuFile"), FileUpload)
    Dim contentType As String = ""
    Dim bytes As Byte() = Nothing

    If FileUpload1.HasFile Then
        contentType = FileUpload1.PostedFile.ContentType
        Using fs As Stream = FileUpload1.PostedFile.InputStream
            Using br As BinaryReader = New BinaryReader(fs)
                bytes = br.ReadBytes(CType(fs.Length, Int32))
            End Using
        End Using
    End If

    Using con As SqlConnection = New SqlConnection(str)
        Dim query As String = "UPDATE tblFiles SET Name = @Name,ContentType = @ContentType,Data=@Data WHERE id = @Id"
        Using cmd As SqlCommand = New SqlCommand(query)
            cmd.Connection = con
            cmd.Parameters.AddWithValue("@Id", id)
            cmd.Parameters.AddWithValue("@Name", fileName)
            cmd.Parameters.AddWithValue("@ContentType", contentType)
            cmd.Parameters.AddWithValue("@Data", If(bytes Is Nothing, New Byte() {}, bytes))
            con.Open()
            cmd.ExecuteNonQuery()
            con.Close()
        End Using
    End Using

    gvFiles.EditIndex = -1
    BindGridView()
End Sub

Protected Sub DownloadFile(ByVal sender As Object, ByVal e As EventArgs)
    Dim id As Integer = Integer.Parse((TryCast(sender, LinkButton)).CommandArgument)
    Dim bytes As Byte()
    Dim fileName, contentType As String
    Using con As SqlConnection = New SqlConnection(str)
        Using cmd As SqlCommand = 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 = CType(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

Private Sub BindGridView()
    Using con As SqlConnection = New SqlConnection(str)
        Using da As SqlDataAdapter = New SqlDataAdapter("SELECT * FROM tblFiles", con)
            Using dt As DataTable = New DataTable()
                da.Fill(dt)
                gvFiles.DataSource = dt
                gvFiles.DataBind()
            End Using
        End Using
    End Using
End Sub