What is the difference between EntityState.Added and EntityState.Modified in Entity Framework?
- EntityState.Added implies the entity is in a detached state, while EntityState.Modified implies it's in an attached state
- EntityState.Added indicates that the entity is being inserted into the database, while EntityState.Modified indicates that the entity has been changed and needs to be updated in the database
- EntityState.Added means the entity is in a transient state, while EntityState.Modified means the entity is being tracked for changes
- EntityState.Added represents a new entity that has been added to the context and is not yet saved in the database, whereas EntityState.Modified indicates that the entity exists in the database and has been modified
EntityState.Added signifies that the entity is newly created and has not been saved to the database yet. EntityState.Modified indicates that the entity already exists in the database but has been modified and needs to be updated when changes are saved.
In ADO.NET, what is the purpose of the AcceptChanges and RejectChanges methods in the DataRow?
- AcceptChanges commits changes to the DataRow
- AcceptChanges discards changes made to the DataRow
- RejectChanges commits changes to the DataRow
- RejectChanges discards changes made to the DataRow
The AcceptChanges method in DataRow commits changes made to the DataRow, effectively updating the DataRow's state to reflect the modifications. On the other hand, the RejectChanges method discards any changes made to the DataRow since it was last updated, reverting it to its original state. These methods are crucial for managing the state of DataRow objects within a DataTable.
Which LINQ operator is used to filter elements in a collection based on a specified condition?
- GroupBy
- OrderBy
- Select
- Where
The "Where" LINQ operator is used to filter elements in a collection based on a specified condition.
What is the difference between optimistic concurrency and pessimistic concurrency in ADO.NET?
- Optimistic concurrency assumes that conflicts between multiple users updating the same data are unlikely, so it allows multiple users to access and modify data concurrently without locking it.
- Optimistic concurrency locks the data when it's being accessed by one user to prevent other users from modifying it simultaneously.
- Pessimistic concurrency allows multiple users to access and modify data concurrently without locking it.
- Pessimistic concurrency assumes that conflicts between multiple users updating the same data are likely, so it locks the data when it's being accessed by one user to prevent other users from modifying it simultaneously.
Optimistic concurrency and pessimistic concurrency are two approaches to handling concurrent data access in ADO.NET. Optimistic concurrency assumes that conflicts between multiple users updating the same data are unlikely, so it allows multiple users to access and modify data concurrently without locking it. Pessimistic concurrency, on the other hand, assumes that conflicts are likely, so it locks the data when it's being accessed by one user to prevent other users from modifying it simultaneously.
To improve query performance in Entity Framework, you can use ___________ loading to retrieve related entities in a single query.
- Deferred
- Dynamic
- Eager
- Lazy
Eager loading allows Entity Framework to load related entities along with the main entity in a single query, thus reducing the number of database round-trips and improving performance. It eagerly loads the related entities as part of the initial query execution. It's suitable for scenarios where you know in advance that you will need the related entities.
Which ADO.NET method is used to open a database connection explicitly?
- Begin()
- Connect()
- Open()
- Start()
The Open() method is used in ADO.NET to explicitly open a database connection. It is a member function of the SqlConnection class, which represents a connection to a SQL Server database. By calling the Open() method, the application establishes a connection to the database, allowing it to execute commands and retrieve data.
What is the primary purpose of non-query commands (INSERT, UPDATE, DELETE) in ADO.NET?
- Creating a new database.
- Establishing a connection to a database.
- Inserting data into, updating data in, or deleting data from a database.
- Retrieving data from a database.
Non-query commands in ADO.NET, such as INSERT, UPDATE, and DELETE, are primarily used for modifying data in a database. These commands allow you to insert new records into a table, update existing records, or delete records from a table. They do not return any data, hence the term "non-query."
To implement custom data binding, you can create a custom class that implements the ___________ interface.
- IBindable
- IDataBinding
- ICustomDataBinding
- INotifyPropertyChanged
The correct option is INotifyPropertyChanged. This interface is commonly used in .NET for implementing custom data binding. It notifies clients that a property value has changed, which is essential for data binding scenarios.
How can parameterized queries help prevent SQL injection attacks?
- By encrypting the SQL commands
- By restricting database access
- By separating data from SQL commands
- By using complex SQL queries
Parameterized queries help prevent SQL injection attacks by separating data from SQL commands. With parameterized queries, user inputs are treated as data rather than executable commands, reducing the risk of malicious SQL injection. Parameters act as placeholders for user-supplied values, preventing attackers from injecting SQL code into the query. This practice enhances security by ensuring that user input is sanitized and properly handled, mitigating the risk of unauthorized access or data manipulation.
A stored procedure is a precompiled ___________ of SQL statements.
- collection
- grouping
- sequence
- set
A stored procedure is a precompiled sequence of SQL statements that are stored in the database and can be executed by applications. They offer advantages such as improved performance as they are precompiled and cached, reducing parsing overhead. Additionally, they provide security by controlling access to data through parameterized queries.