Windows Phone Mango Local Database(SQL CE): How to Update data

published on: 10/27/2011 | Views: N/A | Tags: LocalDB

by WindowsPhoneGeek

This is the 13th post from the "Windows Phone Mango Local Database" series of short posts that will cover all you need to know in order  to get started using a Local Database in Windows Phone 7.1 Mango.  This time I am going to talk about how to update data  when working with a Windows Phone 7.1 Mango local database.

Here is what else is included in this series:

• Windows Phone Mango Local Database(SQL CE): Introduction
• Windows Phone Mango Local Database(SQL CE): Linq to SQL
• Windows Phone Mango Local Database(SQL CE): [Table] attribute
• Windows Phone Mango Local Database(SQL CE): [Column] attribute
• Windows Phone Mango Local Database(SQL CE): [Association] attribute
• Windows Phone Mango Local Database(SQL CE): [Index] attribute
• Windows Phone Mango Local Database(SQL CE): Database mapping
• Windows Phone Mango Local Database(SQL CE): DataContext
• Windows Phone Mango Local Database(SQL CE): Connection Strings
• Windows Phone Mango Local Database(SQL CE): Creating the Database
• Windows Phone Mango Local Database(SQL CE): Database Queries with LINQ
• Windows Phone Mango Local Database(SQL CE): How to Insert data
• Windows Phone Mango Local Database(SQL CE): How to Update data
• Windows Phone Mango Local Database(SQL CE): How to Delete data

Updating data into the database is a three-step process.  First, query the database for the object that is to be updated. Then, modify the object as desired. Finally, call the SubmitChanges method to save the changes to the local database.

NOTE: If you bind objects in the data context to controls on the page, the data context can be updated automatically based on user interaction. Then, the only step required is to call the SubmitChanges method at the desired time.

NOTE: Data is not updated in the database until the SubmitChanges method is called.

For reference you can also take a look at the full MSDN documentation.

How to Update Data?

Before we begin lets assume that we have the following database structure with two tables: Country and City:

The DataContext is as follows:

public class CountryDataContext : DataContext
{
    public CountryDataContext(string connectionString)
        : base(connectionString)
    {
    }
  
    public Table<Country> Countries
    {
        get
        {
            return this.GetTable<Country>();
        }
    }
  
    public Table<City> Cities
    {
        get
        {
            return this.GetTable<City>();
        }
    }
}

In the code sample below we will demonstrate the process of:

• creating the data context
• finding the target "City" that will be updated
• updating the Name of the city to "Madrid"
• finally we will call SubmitChanges() to save the changes back to the database

private void UpdateCity()
{
    using (CountryDataContext context = new CountryDataContext(ConnectionString))
    {
        // find a city to update
        IQueryable<City> cityQuery = from c in context.Cities where c.Name == "Barcelona" select c;
        City cityToUpdate = cityQuery.FirstOrDefault();
         
        // update the city by changing its name
        cityToUpdate.Name = "Madrid";
 
        // save changes to the database
        context.SubmitChanges();
    }
}

In this article I talked about updating data when working with a Windows Phone 7.1 Mango local database. Stay tuned for the rest of the posts.

You may also find interesting the following articles:

• Windows Phone Mango Local Database(SQL CE): Introduction
• Using SqlMetal to generate Windows Phone Mango Local Database classes
• A Simple ToDo List: Persisting Data with the Sterling NoSQL Database
• All about WP7 Isolated Storage series

You can also follow us on Twitter @winphonegeek

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