Databases with LINQ LINQ to SQL uses LINQ

Databases with LINQ

LINQ to SQL uses LINQ syntax to query databases. LINQ to SQL classes are automatically generated by the IDE’s LINQ to SQL Designer. The IDE creates a class for each table, with a property for each column in the table. LINQ queries on an IQueryable object are processed together as a single SQL statement. If each query operator were handled separately, multiple round trips to the database would be needed. A Data. Context class controls the flow of data between the program and the database. When cached objects have been changed, these changes are saved using the Data. Context’s Submit. Changes method.

Display. Table. Books example Select Tools > Connect to Database…. If the Choose Data Source dialog appears, select Microsoft SQL Server Database File from the Data source: List. Box. Click Continue to open the Add Connection dialog. Click Browse… and choose Books. mdf. Right click the project in the Solution Explorer and select Add > New Item… Select LINQ to SQL classes, name the new item Books. dbml and click the Add button. The Database Explorer window allows you navigate the structure of databases. Drag the Authors, Titles and Author. ISBN tables onto the Object Relational Designer and select Yes. Select Data > Add New Data Source… to display the Data Source Configuration Wizard. In the dialog, select Object and click Next >. Expand the tree view and select Display. Table > Author. Click Next > then Finish. The Authors table in the database is now a data source that can be used by the bindings.

Display. Table. Books example Open the Data Sources window by selecting Data > Show Data Sources. Open the Display. Table. Form in Design view. Click the Author node in the Data Sources window—it should change to a drop-down list. Ensure that the Data. Grid. View option is selected. Drag the Author node from the Data Sources window to the Display. Table. Form. The IDE creates a Data. Grid. View with the correct column names and a Binding. Navigator. The Binding. Navigator contains Buttons for moving between entries, adding entries, deleting entries and saving changes to the database. A Binding. Source transfers data between the data source and the data-bound controls on the Form.

Display. Query. Result example More Complex LINQ Queries and Data Binding

Joining. With. LINQ example LINQ to SQL to combine and organize data from multiple tables.

Master. Detailexample Demonstrates a master/detail view—one part of the interface allows you to select an entry, and another part displays detailed information about that entry.

Address. Book example The Address. Book application provides a GUI for querying the database with LINQ. Create a new Windows Forms Application named Address. Book. Add the Address. Book. mdf database and name the file Address. Book. dbml. You must also add the Addresses table as a data source. Click the Address node in the Data Sources window. Click the down arrow to view the items in the list. Select the Details option to indicate that the IDE should create a set of Label/Text. Box pairs. Drag the Address node from the Data Sources window to the Form.