Visual C# | LINQ with Entity Frameworks exercise | Create a form to show events for a continent and category

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.

The answer to the exercise will be included and explained if you attend the course listed below!

Software ==> Visual C#  (79 exercises)
Version ==> Any version of C#
Topic ==> LINQ with Entity Frameworks  (4 exercises)
Level ==> Harder than average
Course ==> Intermediate C#
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help). Once you've done this:
  1. Go into SQL Server Management Studio;
  2. Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
  3. 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).

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If you haven't already got one, create a Windows Forms project (using Visual C#, obviously) called wiseowl. Right-click on your project in Solution Explorer to add an existing item, and choose the file frmChoose.cs in the above folder.

Make this the default form in Program.cs. When you run your application, you should see a form like this:  

Criteria form

Sadly the combo boxes are empty, and the button doesn't do anything! Yet ...

If you haven't already done so, right-click in Solution Explorer and add an ADO.NET Entity Data Model based on the WorldEvents database (tick all of the tables).  

Create LINQ statements to set the data source for the continent combo box to get this:

Two combo boxes

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:

African politics

Africa has 3 politics events in the database.

Check that if a particular continent/category combination has no events, you get a suitable message:

No events message

Africa has no alien events (at least, not in the Wise Owl database).

Give yourself a big pat on the back, and close down your forms. 

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