Questions
C# questions
Choose a question page, learn the concept, then test your understanding with a quiz.
AddTransient vs AddScoped vs AddSingleton in ASP.NET Core Dependency Injection
Learn the differences between AddTransient, AddScoped, and AddSingleton in ASP.NET Core DI with examples and practical usage.
C# Type Checking Explained: typeof vs GetType() vs is
Learn when to use typeof, GetType(), and is in C#. Understand exact type checks, inheritance, and safe type testing clearly.
C# Version Numbers Explained: C# vs .NET Framework and Why “C# 3.5” Is Incorrect
Learn the correct C# version numbers, how they map to .NET releases, and why terms like C# 3.5 are inaccurate and confusing.
C# foreach Closure Behavior Explained: Why Loop Variables Were Reused
Learn why C# foreach loop variables once caused closure bugs, how the compiler handled scope, and what changed in newer C# versions.
Case-Insensitive String.Contains in C#
Learn how to make string.Contains case-insensitive in C#, including StringComparison, examples, pitfalls, and real-world usage.
Const vs Readonly in C#: What's the Difference and When to Use Each
Learn the difference between const and readonly in C#, when each is evaluated, and how to choose the right one in real code.
Convert Byte Arrays to Hex Strings in Java
Learn how to convert a byte array to a hexadecimal string and back in Java with clear examples, common mistakes, and practical use cases.
Create Excel Files in C# Without Microsoft Office Installed
Learn how to create .XLSX and .XLS files in C# without installing Microsoft Office using common libraries and practical examples.
Deep Copy and Object Cloning in C#
Learn how deep copying and object cloning work in C#, with practical examples, pitfalls, and safe ways to duplicate objects.
How to Calculate Age from a DateTime Birthday in C#
Learn how to calculate a person's age in years from a DateTime birthday in C# with clear logic, examples, pitfalls, and best practices.
How to Calculate Relative Time in C#
Learn how to display relative time in C# from a DateTime value, such as '2 hours ago', '3 days ago', or 'a month ago'.
How to Call a Base Class Constructor in C#
Learn how to call a base class constructor in C#, including Exception examples, syntax, common mistakes, and practical usage.
How to Cast an int to an Enum in C#
Learn how to cast an int to an enum in C#, when it works, how to validate values, and common mistakes to avoid.
How to Catch Multiple Exceptions at Once in C#
Learn how to catch multiple exceptions in C#, avoid repetitive catch blocks, and choose cleaner patterns like exception filters and TryParse.
How to Enumerate an Enum in C#
Learn how to enumerate enum values in C# using Enum.GetValues, foreach, and practical examples with common mistakes explained clearly.
How to Generate a Random Integer in C#
Learn how to generate random integers in C# using Random, understand ranges, avoid common mistakes, and see practical examples.
How to Get the Integer Value from an Enum in C#
Learn how to get an int value from an enum in C#, cast enums safely, and pass enum values into methods with practical examples.
How to Give a C# Auto-Property an Initial Value
Learn how to initialize C# auto-properties, when to use constructors, and the modern property initializer syntax with clear examples.
How to Iterate Over a Dictionary in C#
Learn the standard ways to iterate over a Dictionary in C#, including KeyValuePair, keys, values, and common beginner mistakes.
How to Loop Through Enum Values in C#
Learn how to iterate over all enum values in C# using Enum.GetValues, with examples, common mistakes, and practical use cases.
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