<asp:HyperLink  ID="view1" Text="View or Download" runat="Server" NavigateUrl='<%# Eval("Fileid", "Handler.ashx?Fileid={0}") %>' Target="_blank">
                       </asp:HyperLink>

handler file:

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;
using System.Data;
using System.Data.SqlClient;

public class Handler : IHttpHandler 
{
    string constr = "Data Source=DemoServer;Initial Catalog=HRM;User ID=sa;Password=sa123456";
    //DataSet ds=new DataSet();
    SqlCommand cmd = new SqlCommand();
  
    public void ProcessRequest(HttpContext context)
    {
        // get the file id
        Guid Fileid = new Guid(context.Request.QueryString["Fileid"]);
        

        cmd.Connection = new SqlConnection(constr);
        cmd.CommandText = "select * from [Filestbl] where Fileid = @Fileid";
        cmd.Parameters.Add("@Fileid", SqlDbType.UniqueIdentifier).Value = Fileid;
        cmd.Connection.Open();
        SqlDataReader reader = cmd.ExecuteReader();
        if (reader.Read())
        {
            // flush out the binary data to the user
            context.Response.Clear();
            context.Response.ContentType = (string)reader["filetype"];
            context.Response.AddHeader("Content-Disposition", String.Format("inline;filename={0};", reader["filename"].ToString()));
            context.Response.AddHeader("Content-Length", reader["filesize"].ToString());
            context.Response.BinaryWrite((byte[])reader["filecontent"]);
            context.Response.End();
        }

    }
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}