Can't remove Contains() handler from SqlFunctionCallHandler - why?

Question

I'm trying to amend some Entity Framework functionality at runtime by using reflection.
The following code snippets I've been using to get some feeling for the Entity Framework's internal functionality. Please don't ask what I'm using this for - at this stage it's just a test anyway.
My code is supposed to remove the Contains() handler from Entity Framework, so a query like this shall fail:
foreach (T1 a in (from x in ctx.t1
where x.Name.Contains("Man")
select x).DefaultIfEmpty()) if (a != null) Console.WriteLine(a.Name);
However, I don't seem to be able to remove the Contains handler at run-time.
Can someone please enlighten me on why this doesn't work?
Here's the code I've been using (I've omitted as much as I could to make the code snippet small):
using System;
using System.Data.Entity;
using System.Data.Entity.SqlServer;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
namespace EF_Contains_Override
internal class Program
static private void removeContains()
Type type = Assembly.GetAssembly(typeof(SqlFunctions)).GetType("System.Data.Entity.SqlServer.SqlGen.SqlFunctionCallHandler");
FieldInfo fi = type.GetField("_canonicalFunctionHandlers", BindingFlags.Static | BindingFlags.NonPublic);
object functionHandlerList = fi.GetValue(null);
MethodInfo method = functionHandlerList.GetType().GetMethod("get_Item", new Type[] { typeof(string) });
object origContains = method.Invoke(functionHandlerList, new object[] { "Contains" });
method = functionHandlerList.GetType().GetMethod("Remove", new Type[] { typeof(string) });
Debug.Assert((bool)method.Invoke(functionHandlerList, new object[] { "Contains" }));
static private void Main(string[] args)
Database.SetInitializer<EFContains>(new MyInitializer());
removeContains();
using (EFContains ctx = new EFContains())
foreach (T1 a in (from x in ctx.t1
where x.Name.Contains("Man")
select x).DefaultIfEmpty()) if (a != null) Console.WriteLine(a.Name);
Console.WriteLine("Press any key to continue ...");
Console.ReadKey();
Given the following seed, the above select should throw an exception because a Contains() handler no longer exists:
using System.Data.Entity;
namespace EF_Contains_Override
public class MyInitializer : DropCreateDatabaseAlways<EFContains>
protected override void Seed(EFContains context)
context.t1.AddRange(new[] { new T1("Hey Man"), new T1("No, woman, no cry") });
context.SaveChanges();
Still people out there alive using the keyboard?
Working with SQL Server/Visual Studio/Office/Windows and their poor keyboard support they seem extinct...

Answer 1

Hello BetterToday,
With your provided code and the resource code of Entity Framework downloaded from
here, I created a similar query with yours:
using (DFDBEntities db = new DFDBEntities())
var result = (from o in db.TestTables
where o.TestName.Contains("1")
select o).ToList();
With the resource, the all method are called to help generate the T-SQL are:
SqlGenerator.GenerateSql, SqlGenerator. VisitExpressionEnsureSqlStatement, SqlGenerator. VisitFilterExpression,
 and in the SqlGenerator.Visit, we see that it converts the Contains to the Like filer and then it called method is WriteSql, we can see that the static class System.Data.Entity.SqlServer.SqlGen.SqlFunctionCallHandler is not called, so it
would does not affect query even after removing the contains method.
After searching more, my consult is that for methods as Contains/StartWith/EndWith and some other methods could be translated to TSQL directly, this behavior are by designed.
You could try with other method as the 'TOLOWER' as:
static void Main(string[] args)
try
#region https://social.msdn.microsoft.com/Forums/en-US/82aaca54-f1cd-47d3-b97c-254ec7b3e8bf/cant-remove-contains-handler-from-sqlfunctioncallhandler-why?forum
removeContains();
using (DFDBEntities db = new DFDBEntities())
var result = (from o in db.TestTables
where o.TestName.ToLower() == "1"
select o).ToList();
#endregion
catch (Exception)
static private void removeContains()
Type type = Assembly.GetAssembly(typeof(SqlFunctions)).GetType("System.Data.Entity.SqlServer.SqlGen.SqlFunctionCallHandler");
FieldInfo fi = type.GetField("_canonicalFunctionHandlers", BindingFlags.Static | BindingFlags.NonPublic);
object functionHandlerList = fi.GetValue(null);
MethodInfo method = functionHandlerList.GetType().GetMethod("get_Item", new Type[] { typeof(string) });
object origContains = method.Invoke(functionHandlerList, new object[] { "ToLower" });
method = functionHandlerList.GetType().GetMethod("Remove", new Type[] { typeof(string) });
Debug.Assert((bool)method.Invoke(functionHandlerList, new object[] { "ToLower" }));
It would throw an which says “{"'TOLOWER' is not a recognized built-in function name."}” I think it is you except.
Regards.
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