Developing the query code in C#.NET

Making Code-39 in C#.NET Developing the query code

Creating the code for this example is similar to working with the LINQ to SQL example You create a data context, make the query, and process the output The example doesn t require a mapping file to work properly The output processing, however, requires a little more work, as shown in Listing 13-7

private void btnTest_Click(object sender, EventArgs e) { // Create the Data Context object Northwind DB = new Northwind( new MySqlConnection( server=localhost;user id=ODBC; + password=;database=Northwind )); // Define the query

(continued)

Listing 13-7 (continued)

var ThisQuery = from Cust in DBCustomers select Cust; // Build a table from the data DataTable ThisTable = new DataTable(); ThisTableColumnsAdd( Customer ID ); ThisTableColumnsAdd( Company Name ); ThisTableColumnsAdd( Contact Name ); // Move the data from the results to the table foreach (var ThisRow in ThisQuery) { // Create the data row DataRow AddRow = ThisTableNewRow(); // Add the data AddRow[ Customer ID ] = ThisRowCustomerID; AddRow[ Company Name ] = ThisRowCompanyName; AddRow[ Contact Name ] = ThisRowContactName; // Place the data in the table ThisTableRowsAdd(AddRow); } // Display the results dgResultDataSource = ThisTable; } The string for the data context is slightly different The connection requires that you provide a server name, user name, password, and database name MySQL doesn t support Windows authentication The query is the same as any query you create using LINQ to SQL In fact, you could possibly move the queries from one environment to the other without changes in at least most cases Unfortunately, you can t simply assign the output, ThisQuery, to the dgResultDataSource property as you can with LINQ to SQL The output is blank when you do, even when the query is successful You have to build a table from scratch and work with the data directly Consequently, the DB LINQ provider doesn t provide quite as much automation as LINQ to SQL However, the important point is that it does work As shown in Listing 13-7, you transfer the data by building a DataTable much as you would with any other complex data query The example uses a foreach loop to extract the individual rows from ThisQuery and place them in ThisRow The code then builds individual DataRow objects, AddRow, and places them in ThisTable using the ThisTableRowsAdd() method call

his part of the book is all about tens In 14 you discover ten new ways to make the LINQ application development process easier 15 moves from development to LINQ application support You find out about ten new ways to keep both users and support staff happy, which makes less work for you Everyone likes to have tools and resources that make things easier 16 discusses ten tools or resources you can use to make working with LINQ significantly easier Even though LINQ has only recently appeared in the marketplace, third parties are already working feverishly to make your job easier Check out these tools and resources when you have a special need for creating better applications

14

Simplifying code using LINQ tools Creating self-documenting code using LINQ Performing code pattern analysis Defining a code snippet database Using LINQ to find other development resources Understanding data format using LINQ Discovering usage trends Creating your own LINQ library Trading useful LINQ queries with others Performing compilation and code analysis

hroughout this book, you see a myriad of ways in which you can use LINQ to create applications Of course, knowing you can use a technology and understanding that it will improve your development experience are two different things By now, you know that LINQ can help you produce shorter code, but this chapter helps you discover why shorter code doesn t translate into harder to read code LINQ is quite easy to read, and because it uses the same form with every query, it provides a solid method for creating self-documenting code Anyone who sees one LINQ query can easily read most other LINQ queries of the same complexity The first question that this chapter answers, therefore, is whether LINQ provides something of value to you as an individual developer it answers the questions of whether easy to use and easy to read translate into meaningless technology The first question begs a second question, the one that most developers ask about coding efficiently and maximizing potential This chapter also helps you get the most out of LINQ After you begin working with LINQ, you may discover a need to make LINQ do more It s easy to get excited about the capabilities that LINQ provides and equally easy to become frustrated when