Microsoft® SQL Server® 2008 Bible

Chapter 34. LINQ

IN THIS CHAPTER

• Overview and history of LINQ

• Understanding LINQ

• LINQ standard query operators

• Syntax options

• LINQ to SQL

• LINQ to XML

• LINQ to Dataset

• LINQ to Entities

Let's get right to the point. I often see code like this:

string ConnectionString = @"Data Source=(local);
Initial Catalog = Adventureworks;UID=username;PWD=password";
using (SqlConnection conn = new
SqlConnection(ConnectionString))
{
    conn.Open();
    SqlCommand cmd = conn.CreateCommand();
    cmd.CommandType = CommandType.Text;
    cmd.CommandText = "SELECT LastName, FirstName,
MidleName FROM Person.Contact";
    using (SqlDataReader rdr = cmd.ExecuteReader())
    {
        // do something
    }
}

Maybe you have also seen code like this or have even done it yourself, but at some point in your career one of the two have happened. Given the preceding code, ask yourself two questions. First, will it compile when run? Second, if so, will it run successfully? Set aside for a minute the fact that there is no WHERE clause and ignore the lack of encapsulation. That is not the intent of this example. What is important are the two questions.

First, yes, it will compile. Second, when it runs it will fail. It will fail because the column "MidleName" should actually be "MiddleName." The problem is that you need to run the program in order to catch this. Even worse, if your program does error, where do you look? (That is, the developer was unaware that the column name was misspelled.) Debugging an error such as this is time consuming and unproductive. Equally, ...