In LINQ, what is deferred execution, and why is it important?
- It executes queries asynchronously to prevent blocking.
- It executes queries in parallel to improve performance.
- It is the immediate execution of queries to retrieve data.
- It postpones the execution of queries until the results are needed.
Deferred execution in LINQ means that the query is not executed immediately when it is defined, but rather when the results are actually accessed. This is important because it allows for more efficient use of resources by delaying the execution until necessary, which can lead to better performance and reduced memory consumption, especially when dealing with large datasets or complex queries.
When optimizing LINQ queries, using the ___________ method can help in reducing the number of database round trips.
- FirstOrDefault()
- Include()
- Skip()
- ToList()
The correct answer is ToList(). When you use ToList() method, it retrieves all the data from the database at once and then performs operations on it in memory. This can reduce the number of database round trips by fetching all data needed in a single trip, potentially improving performance.
In LINQ, what is the purpose of the select clause?
- To filter the results
- To join the results
- To project the results
- To sort the results
The purpose of the select clause in LINQ is to project the results. It allows you to define the shape of the result set by selecting specific fields or transforming the elements of the source sequence into a new form.
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.