101
What is the difference between reference equality and value equality in C#?
Reference equality checks whether two reference variables point to the same object instance. Value equality checks whether two objects represent the same logical value.
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Types, Equality, Immutability & Internals
C# interview questions covering types, equality, immutability & internals.
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102
What is IEquatable<T>, and when should it be implemented?
IEquatable<T> defines a strongly typed Equals(T?) method for value equality. It avoids relying only on object.Equals and can reduce boxing for value types.
103
What is immutability in C#?
An immutable object cannot have its observable state changed after creation. Instead of modifying an existing object, code creates a new value representing the changed state.
104
What is a readonly struct?
A readonly struct is a value type whose instance fields must be readonly and whose instance state cannot be modified after construction.
105
What is the difference between shallow copy and deep copy?
A shallow copy creates a new outer object but copies references to nested reference-type objects. Therefore, the original and copy may still share child objects.
106
What is covariance and contravariance in C# generics?
Variance controls how generic types relate when their type arguments have an inheritance relationship.
107
What is a generic method, and how does type inference work?
A generic method declares one or more type parameters independently of whether the containing class is generic.
108
What is the default keyword in C#?
The default keyword produces the default value of a type. For numeric value types it is zero, for bool it is false, and for reference types it is null.
109
What is nameof in C#, and why is it useful?
nameof returns the source-code name of a variable, type, property, method, or other symbol as a string.
110
What is the difference between typeof, GetType(), and is?
typeof obtains a Type object for a type known at compile time. GetType() obtains the actual runtime type of an object instance. The is operator tests whether an object is compatible with a specified type or pattern.