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Software ==>	Visual C# (55 exercises)
Topic ==>	LINQ with Entity Frameworks (4 exercises)
Level ==>	Average difficulty
Subject ==>	C# training

Use LINQ to add rows to two different tables, saving your changes

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.

On June 3rd 2018 the Guatemalan volcano Fuego erupted - this event needs to be added to the tblEvent table (but first Guatemala needs to be added to the tblCountry table).

There are many more events which could be added too - COVID and the Russian invasion of Ukraine spring to mind - but every long journey starts with a single step ...

Create a new form called frmVolcano with a single clickable button. When you click on this button your code should:

Task	Notes
Add a country	Guatemala isn't in the tblCountry table, so create a new tblCountry object, set its CountryName property, add it to your data context's collection of countries and then save changes for the data context!
Add an event	Similarly add the eruption event into the tblEvent table. Use category id number 4 (this corresponds to Natural World events). You'll need to set the CountryId, CategoryId, EventDate, EventName and EventDetails properties.

Before displaying details of the event you've just added, you need to refresh the data context. One fairly primitive way to do this is to dispose of it and then recreate it:

// save these changes

dbEvents.SaveChanges();

// make sure have latest changes

dbEvents.Dispose();

dbEvents = new WorldEventsEntities();

Now use LINQ to get the event whose id number equals the id number of the event you've just added, then display these details in a message box:

Your message could look something like this.

Finally, add code to remove the event with the id number that you've just added, using code something like this:

// now remove this event

dbEvents.tblEvents.Remove(newEvent);

dbEvents.SaveChanges();

We'll leave Guatemala in the countries table for posterity!

You can unzip this file to see the answers to this exercise, although please remember this is for your personal use only.

You can find other training resources for the subject of this exercise here:

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EXERCISE TOPIC

C# EXERCISES

VISUAL C# EXERCISES

Use LINQ to add rows to two different tables, saving your changes

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