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LINQ and Dynamic Predicate Construction at Runtime

, 13 Aug 2008
Illustrating a multi-predicate injection pattern now possible with the new features of C# 3.0.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.SessionState;
using System.Data.SqlClient;

namespace LINQDynamicSearchDemo {
    public class Global : System.Web.HttpApplication {

        protected void Application_Start(object sender, EventArgs e) {
          /*  using (SqlConnection conn = new SqlConnection(@"Data Source=.\SQLExpress;Database=master;Integrated Security=True;")) {
                using (SqlCommand cmd = conn.CreateCommand()) {
                    cmd.CommandType = System.Data.CommandType.StoredProcedure;
                    cmd.CommandText = "sp_attach_single_file_db";

                    cmd.Parameters.AddWithValue("@dbname", "Northwind");
                    cmd.Parameters.AddWithValue("@physname", Server.MapPath("~/App_Data/NORTHWND.MDF"));

        protected void Session_Start(object sender, EventArgs e) {


        /// <summary>
        /// starting the request, build a context and stash it
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Application_BeginRequest(object sender, EventArgs e) {
            NorthwindDBDataContext ctx = new NorthwindDBDataContext();
            HttpContext.Current.Items["RequestContext"] = ctx;


        /// <summary>
        /// when the request is over, kill the context
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Application_EndRequest(object sender, EventArgs e) {
            NorthwindDBDataContext ctx = HttpContext.Current.Items["RequestContext"] as NorthwindDBDataContext;
            // kill it proper-like
            if (ctx != null) {

        protected void Application_AuthenticateRequest(object sender, EventArgs e) {


        protected void Application_Error(object sender, EventArgs e) {


        protected void Session_End(object sender, EventArgs e) {


        protected void Application_End(object sender, EventArgs e) {


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About the Author


United States United States
Dave works all day, and stays up all night coding and reading, surfing the intertubes.

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Web03 | 2.8.140922.1 | Last Updated 14 Aug 2008
Article Copyright 2008 by dave.dolan
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