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Software ==>	Visual C# (55 exercises)
Topic ==>	LINQ with Entity Frameworks (4 exercises)
Level ==>	Harder than average
Subject ==>	C# training

Populate two combo boxes in a form, and use criteria to list out events

This exercise is provided to allow potential course delegates to choose the correct Wise Owl Microsoft training course, and may not be reproduced in whole or in part in any format without the prior written consent of Wise Owl.

Before you can do this exercise, you'll need to download and unzip this file . Once you've done this:

Go into SQL Server Management Studio;
Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
Execute this script.

This will generate the database that you'll need to use in order to do this exercise (note that the database and script are only to be used for exercises published on this website, and may not be reused or distributed in any form without the prior written permission of Wise Owl).

If you haven't already done so, go into SQL Server Management Studio and open the file in the above folder and run its script. This should generate a WorldEvents database. Create an ADO entity model based upon this database.

The method of creating an entity model is not given here, since it varies according to which version of Windows Forms, Visual Studio, LINQ to SQL Classes and Entity Frameworks you are using. If in doubt, ask your trainer!

Here is one version of the entity framework to show you which tables and fields you can reference:

The database contains four tables with relationships between them.

Create a form called frmChoose to contain two combo boxes and a clickable button as shown below, then create LINQ statements to set the data source for the continent combo box to get this:

When you open the form, the combo box should show a list of the continents in the database (although it's actually the continent id which is being stored).

Your LINQ statement should return an anonymous type containing two fields

Field	What it should hold
Id	The id number of the continent
Name	The name of the continent

You can then run these statements to populate the combo box:

cmbCategory.ValueMember = "Id";

cmbCategory.DisplayMember = "Name";

// set this to be basis for combo box

cmbCategory.DataSource = categories.ToList();

In a similar way, populate the category combo box.

Add a datagridview to the bottom of the form. Run a third LINQ statement from the button, so that when you click on it you see a list of all of the events for the continent and category you've chosen. For example: