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Databases, data science & more

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Publisher ‏ : ‎ O’Reilly Media; 1st edition (April 3, 2012)
Language ‏ : ‎ English
Paperback ‏ : ‎ 254 pages
ISBN-10 ‏ : ‎ 1449312969
ISBN-13 ‏ : ‎ 978-1449312961
Item Weight ‏ : ‎ 15.9 ounces
Dimensions ‏ : ‎ 7 x 0.54 x 9.19 inches

Programming Entity Framework: DbContext: Querying, Changing, and Validating Your Data with Entity Framework

Entity Framework is a powerful and flexible ORM (Object-Relational Mapping) framework that simplifies data access and manipulation in .NET applications. The DbContext class is a core component of Entity Framework, responsible for managing the connection to the database, querying data, and tracking changes.

In this post, we will explore how to effectively use the DbContext class to query, change, and validate your data in Entity Framework.

Querying Data with DbContext:

The DbContext class provides various methods for querying data from the database. You can use LINQ (Language Integrated Query) to write queries and retrieve data in a strongly-typed manner. Here’s an example of querying data using DbContext:

using (var context = new MyDbContext())<br />
{<br />
    var products = context.Products.Where(p => p.Category == "Electronics").ToList();<br />
}<br />
```<br />
<br />
In this example, we are querying all products in the "Electronics" category from the database using the Where method and converting the results to a list.<br />
<br />
Changing Data with DbContext:<br />
<br />
The DbContext class also allows you to change data in the database by adding, updating, or deleting entities. You can use methods like Add, Update, and Remove to make changes to the data. Here's an example of changing data using DbContext:<br />
<br />
```csharp<br />
using (var context = new MyDbContext())<br />
{<br />
    var product = new Product { Name = "Laptop", Category = "Electronics" };<br />
    context.Products.Add(product);<br />
    context.SaveChanges();<br />
}<br />
```<br />
<br />
In this example, we are adding a new product to the database using the Add method and saving the changes to the database using the SaveChanges method.<br />
<br />
Validating Data with DbContext:<br />
<br />
Entity Framework provides built-in validation mechanisms to ensure the integrity and consistency of your data. You can use data annotations, fluent API, or custom validation logic to validate entities before saving changes to the database. Here's an example of validating data using DbContext:<br />
<br />
```csharp<br />
public class Product<br />
{<br />
    [Required]<br />
    public string Name { get; set; }<br />
<br />
    [Range(0, double.MaxValue)]<br />
    public decimal Price { get; set; }<br />
}<br />
```<br />
<br />
In this example, we are using data annotations to specify that the Name property is required and the Price property must be a non-negative value.<br />
<br />
In conclusion, the DbContext class in Entity Framework is a powerful tool for querying, changing, and validating your data. By leveraging its capabilities effectively, you can build robust and maintainable data access layers in your .NET applications.

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