Cognizant DOT NET Developer Interview Questions and Answers

Q1. What is the repository design pattern?
Ans. 
Repository design pattern is a design pattern that separates the data access logic from the business logic in an application.
• It helps in achieving separation of concerns by isolating the data access code in a separate layer.

• It provides a centralized way to access data from various sources such as databases, web services, etc.

• It makes the codebase more maintainable and testable by abstracting the data access logic.

• Examp...read more
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Q2. What is the difference between IEnumerable and IQueryable?
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IEnumerable is used for in-memory collection operations, while IQueryable is used for database query operations.
• IEnumerable is used for querying data from in-memory collections like arrays, lists, etc.

• IQueryable is used for querying data from a database using LINQ to SQL or Entity Framework.

• IEnumerable executes the query in-memory, while IQueryable executes the query on the database server.

• IEnumerable is suitable for L...read more
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Q1. How to call abstract constructor
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Q2. Difference between generic list and list which is faster
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Q1. What is the extension method
Ans. 
Extension methods allow adding new methods to existing types without modifying the original type
• Extension methods are static methods that can be called as if they were instance methods of the extended type

• They are defined in static classes and must be in the same namespace as the extended type

• They are commonly used to add functionality to existing types or interfaces without modifying them directly
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Q2. What is difference between union and union all
Ans. 
Union combines and removes duplicates, Union All combines without removing duplicates.
• Union removes duplicates from the result set, while Union All does not.

• Union is slower than Union All because it has to perform an additional step to remove duplicates.

• Union is used when you want to combine two result sets and remove duplicates, while Union All is used when you want to combine two result sets without removing duplicat
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Q3. What is constructor chaining
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Constructor chaining is the process of calling one constructor from another constructor within the same class.
• Allows for reusing code and avoiding duplication

• Can be achieved using 'this' keyword in the constructor

• Example: public MyClass(int x) : this(x, 0) {}
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Q4. What is CTE and explain
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CTE stands for Common Table Expressions, which is a temporary result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement.
• CTEs are defined using the WITH keyword in SQL.

• They help improve readability and maintainability of complex queries.

• CTEs can be recursive, allowing for hierarchical data querying.

• Example: WITH CTE AS (SELECT * FROM table_name) SELECT * FROM CTE;

• Example: WITH RECURSIVE CTE ...read more
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Q5. What is constructor
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A constructor is a special method in a class that is automatically called when an object of that class is created.
• Constructors have the same name as the class they belong to.

• They are used to initialize the object's state.

• Constructors can be parameterized or default (no parameters).

• Example: public class Person { public Person(string name) { this.Name = name; } }
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Q6. How to send bulk of data through db
Ans. 
Use bulk insert or batch processing to send large amounts of data through the database.
• Use bulk insert operations provided by the database management system.

• Consider using batch processing techniques to optimize performance.

• Use stored procedures or parameterized queries for efficient data transfer.
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Q7. Which design pattern do you used in your project
Ans. 
I have used the MVC (Model-View-Controller) design pattern in my project.
• Separates the application into three main components: Model, View, and Controller

• Promotes code reusability, modularity, and maintainability

• Example: ASP.NET MVC framework
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Q8. What are the characteristics of singleton pattern and how to use
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Singleton pattern ensures a class has only one instance and provides a global point of access to it.
• Characteristics include private constructor, static instance variable, static method to access instance, lazy initialization, and thread safety.

• Example: public class Singleton { private static Singleton instance; private Singleton() {} public static Singleton getInstance() { if (instance == null) { instance = new Singlet
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Q9. Write a linq to fetch the data from db table(students) and data (studentid) should be in asending rder
Ans. 
Use LINQ to fetch data from the 'students' table in ascending order of 'studentid'.
• Use LINQ query syntax or method syntax to retrieve data from the 'students' table.

• Order the data by 'studentid' in ascending order using the 'OrderBy' or 'OrderByDescending' method.

• Ensure that the LINQ query is executed against the database to fetch the data.
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