What is a Namespace in C#?
💡 Concept: Namespace in C#
A namespace in C# is a way to logically group classes, interfaces, structs, enums, and delegates. It helps avoid naming conflicts and organizes code into manageable sections.
📘 Quick Intro to Namespace
Namespaces are fundamental in C# to ensure that code elements don't conflict. For example, two classes with the same name can exist in different namespaces.
🧠 Analogy: Namespace
Imagine namespaces like folders on your computer. You can have a file named Invoice.txt in two different folders. Similarly, you can have a class Invoice in two different namespaces without any clash.
🔧 Technical Explanation
- Namespaces are declared using the
namespacekeyword. - They can be nested to form hierarchical structures.
- The
usingdirective allows access to a namespace without specifying its full path. - Helps avoid class name collisions in large projects or third-party libraries.
- Common namespaces include
System,System.Collections.Generic, etc.
🎯 Use Cases for Namespace
- Organizing related classes (e.g.,
MyApp.ServicesandMyApp.Models). - Preventing naming collisions with other libraries.
- Grouping reusable components for modular design.
- Maintaining cleaner and scalable architecture.
- Providing structure to large enterprise-level applications.
💻 C# Code Example: Namespace
namespace MyApp.Services {
public class EmailService {
public void Send(string to) {
Console.WriteLine($"Sending email to {to}");
}
}
}
namespace MyApp.Models {
public class User {
public string Name { get; set; }
}
}
❓ Interview Q&A
Q1: Why are namespaces used in C#?
A: To organize code and prevent name conflicts.
Q2: Can namespaces be nested?
A: Yes, nested namespaces provide more structure.
Q3: What does the using directive do?
A: It allows use of classes without writing the full namespace path.
Q4: What is the global namespace?
A: It is the default unnamed namespace for unqualified types.
Q5: Can two classes with the same name exist in different namespaces?
A: Yes, that’s one of the key benefits of namespaces.
Q6: How do you access a class from a different namespace?
A: By using its fully-qualified name or the using statement.
Q7: Is System a namespace?
A: Yes, it’s a base namespace in .NET.
Q8: What are some common .NET namespaces?
A: System, System.IO, System.Linq, etc.
Q9: Can a file include multiple namespaces?
A: Yes, a file can define multiple namespaces.
Q10: Can namespaces contain interfaces and enums?
A: Yes, along with classes, structs, and delegates.
📝 MCQs
Q1. Why are namespaces used in C#?
- To speed up compilation
- To format code
- To organize and avoid naming conflicts
- To declare memory
Q2. Which keyword is used to declare a namespace?
- package
- module
- namespace
- folder
Q3. Can namespaces be nested?
- No
- Only two levels
- Yes
- Only with classes
Q4. What does the using directive do?
- Creates a namespace
- Imports libraries
- Provides access to a namespace
- None of the above
Q5. Which of the following is a valid .NET namespace?
- Net.IO
- Sys.IO
- System.IO
- Microsoft.IO
Q6. Can a class exist without a namespace?
- No
- Yes, in the global namespace
- Only in System
- Only in nested
Q7. What is a fully qualified name?
- Method signature
- Class with parameters
- Complete name including namespace
- Name with return type
Q8. Can two classes have the same name in different namespaces?
- No
- Only with inheritance
- Yes
- Only static classes
Q9. Which statement is true about using directive?
- It creates namespaces
- It declares variables
- It allows access without full name
- It optimizes performance
Q10. Is System a namespace?
- No
- Only in VB
- Yes
- It is a class
💡 Bonus Insight
Namespaces are critical in building scalable software. Good namespace structure reflects your application architecture, simplifies dependency injection, and reduces cognitive load when reading code.
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