Querying nullable fields using linq is a tricky task. Let's create a simple sql table and start some testing using linqpad
Our table schema should look like the following;

USE [TestData]
GO

/****** Object:  Table [dbo].[Patterns]    Script Date: 05/27/2011 09:20:12 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[Patterns](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[ParentID] [int] NULL,
	[PatternName] [nvarchar](150) NOT NULL,
	[CreatedBy] [nvarchar](50) NULL,
 CONSTRAINT [PK_Patterns] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
/****** insert some test data ******/
insert into patterns values(2,'Pattern 1',null)
insert into patterns values(2,'Pattern 2',null)
insert into patterns values(3,'Pattern 3','Cathy')
insert into patterns values(4,'Pattern 4',null)
insert into patterns values(5,'Pattern 5',null)
insert into patterns values(null,'Pattern 6','Joe')
insert into patterns values(null,'Pattern 7',null)

  Now we have our table and data in place,lets create a method to query our data

void QueryPatternsWithNullCreatedBy(string userName)
	{
	var patterns = from x in Patterns
	where x.CreatedBy==userName
	orderby x.Id
	select x;
	patterns.Dump(); //Dump() method is a linqpad extension method
	
	}

Call number 1 will send null as the userName param

QueryPatternsWithNullCreatedBy(null);

 Why aren't we getting any data returned? Whatever happened to the five rows we just inserted with null CreatedBy value?

let's examine the generated SQL to see what happened

DECLARE @p0 NVarChar(1000) = null
SELECT [t0].[Id], [t0].[ParentID], [t0].[PatternName], [t0].[CreatedBy]
FROM [Patterns] AS [t0]
WHERE [t0].[CreatedBy] = @p0
ORDER BY [t0].[Id]

  Here is our aha moment, the generated SQL is querying the string literal 'null'

To get linq to change the generated SQL and use Is Null we can change the query in our method to

void QueryPatternsWithNullCreatedBy(string userName)
	{
	var patterns = from x in Patterns
	where object.Equals(x.CreatedBy,userName)
	orderby x.Id
	select x;
	patterns.Dump();
	
	}

 Now we see our generated SQL is creating the correct query

SELECT [t0].[Id], [t0].[ParentID], [t0].[PatternName], [t0].[CreatedBy]
FROM [Patterns] AS [t0]
WHERE [t0].[CreatedBy] IS NULL
ORDER BY [t0].[Id]

 Call number 2:

QueryPatternsWithNullCreatedBy("joe");

Will return a single row as expected using both queries

Enjoy 

Today We needed to add an HTML string in the web.config. This string will be used in multiple methods and classes as a replacement holder.
The html is nothing but a simple HTML table
Here is what we ended up with in the appSettings section of the web.config

<appSettings>
<add key="htmlTable">
      <value><![CDATA["<table><tr><td>{TOREPLACE}</td></tr></table>"]></value>
</add>
 </appSettings>

Enjoy.