Using a Web Farm in ASP.NET in visual C#.net

Generator PDF 417 in visual C#.net Using a Web Farm in ASP.NET

The last of our chapters on LINQ relates to the System.Data.DataSet class, which can be used to create an in-memory cache of data from a database and which can be used as the data source for LINQ queries. The DataSet class is part of ADO.NET just like the Entity Framework that we saw in the previous chapter. ADO.NET is big; it allows you to access a wide range of data sources in a wide range of ways. In this chapter, we ll be looking at working with databases more directly than with the Entity Framework. We won t be using data models or C# objects that represent tables and rows. In fact, if you have been waiting for a chance to break out your SQL skills, then this is the chapter for you. ADO.NET supports all the major databases and quite a few of the minor ones. We won t be going into the details of setting up and configuring a database, and our examples will all be based on SQL Server Express. That said, everything you learn in this chapter can be transferred to other database servers because of the way that ADO.NET provides consistent access to data and databases. Table 31-1 provides the summary for this chapter. Table 31-1. Quick Problem/Solution Reference for 31

The last of the generic list collection classes is SortedList<TKey, TVal>. However, oddly, this class isn t a list at all. It implements the IDictionary<TKey, TVal> interface, which we ll see more of when we get to the Generic Dictionaries section of this chapter. In fact, this class is a kind of cross-over between a list and a dictionary. The difference from List<T> is that the items are sorted as they are added. This is different from List<T> where the items are stored in the sequence they are added until the Sort method is used. The SortedList<TKey, TVal> class has six constructors, which are listed in Table 19-14. Table 19-14. Constructors for SortedList<TKey, TVal>

The following code shows a full program, including class MyData and extension method Average declared in class ExtendMyData. Notice that method Average is invoked exactly as if it were an instance member of MyData! Figure 7-21 illustrates the code. Classes MyData and ExtendMyData together act like the desired class, with three methods. namespace ExtensionMethods { sealed class MyData { private double D1, D2, D3; public MyData(double d1, double d2, double d3) { D1 = d1; D2 = d2; D3 = d3; } public double Sum() { return D1 + D2 + D3; } } static class ExtendMyData Keyword and type { public static double Average(this MyData md) { Declared static return md.Sum() / 3; } } class Program { static void Main() { MyData md = new MyData(3, 4, 5); Console.WriteLine("Sum: {0}", md.Sum()); Console.WriteLine("Average: {0}", md.Average()); } } Invoke as an instance member of the class } This code produces the following output: Sum: 12 Average: 4

The Csla project is a Class Library, and it targets the .NET Framework 3.5 SP1. You can see these settings in Visual Studio by double-clicking the Properties node under the Csla project in Solution Explorer and looking at the Application tab, as shown in Figure 6-1.

Many developers use Web.config file to hold application specific settings, such as database connection strings. The trouble with Web.config is that when you deploy your applications, you normally have to change these settings. VS2010 offers the ability to create a build configuration that allows you to modify the contents of the Web.config file for different build configurations. Note you can also use this feature on Web.config files in sub folders. VS2010 actually uses this functionality already when you switch between debug/release mode, let s take a look at this now.