Questions
C# questions
Choose a question page, learn the concept, then test your understanding with a quiz.
How to Group by Multiple Columns in LINQ (C#)
Learn how to group by multiple columns in LINQ using C#. See syntax, examples, execution steps, common mistakes, and a practical mini project.
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.
How to Mark a Method as Obsolete or Deprecated in C#
Learn how to deprecate methods in C# using the Obsolete attribute, with examples, warnings vs errors, and migration tips.
How to Pass a Method as a Parameter in C# Using Delegates
Learn how to pass a method as a parameter in C# using delegates, Func, and lambdas with simple examples and common mistakes.
How to Query a DataTable with LINQ in C#
Learn how to use LINQ with DataTable in C#. Understand AsEnumerable, Field<T>(), filtering rows, and common mistakes with DataTable queries.
How to Randomize a List<T> in C#
Learn how to shuffle a List<T> in C# correctly using Random and the Fisher-Yates algorithm for lottery apps and other practical cases.
How to Read app.config and web.config Settings in .NET Class Libraries
Learn how to read app.config or web.config settings in a .NET class library using ConfigurationManager and modern .NET config practices.
How to Run a .NET Application as Administrator on Windows 7
Learn how a .NET app requests administrator rights on Windows 7 using manifests, UAC, and elevation best practices.
How to Send an HTTP POST Request in .NET
Learn how to send HTTP POST requests in .NET, including JSON bodies, form data, headers, and best practices with HttpClient.
How to Set the Content-Type Header with HttpClient in C#
Learn how to correctly set the Content-Type header in C# HttpClient requests and avoid the Misused header name exception.
How to Sort a Dictionary by Value in C#
Learn how to sort a Dictionary by value in C# using LINQ, with examples, pitfalls, and practical patterns for real projects.
How to Sort a List<T> by an Object Property in C#
Learn how to sort a List<T> by object properties in C# using Sort, LINQ OrderBy, ThenBy, and custom comparisons.
How to Split a String by Newlines in .NET (C#)
Learn how to split a string by newlines in .NET using C# with Split, Environment.NewLine, and mixed line ending handling.
How to Update the GUI from Another Thread in C# WinForms
Learn the safe way to update a WinForms Label from another thread in C#, using Invoke, BeginInvoke, and thread-safe UI patterns.
How to Use GroupBy in LINQ to Group Objects and Collect Values in C#
Learn how to use LINQ GroupBy in C# to group people by PersonID and collect related values like car names into lists.
How to Use LINQ Distinct by Property in C#
Learn how to get distinct objects by one or more properties in C# using LINQ, equality comparers, GroupBy, and modern DistinctBy examples.
IEnumerable vs List in C#: LINQ Execution and Performance
Learn when to use IEnumerable<T> or List<T> in C#, how LINQ queries execute, and when ToList() improves safety or performance.
IQueryable vs IEnumerable in C#: Differences, Deferred Execution, and When to Use Each
Learn the difference between IQueryable and IEnumerable in C#, how deferred execution works, and when to return each in real applications.
Implement INotifyPropertyChanged Gracefully in C#
Learn practical ways to implement INotifyPropertyChanged in C#, including SetProperty helpers, CallerMemberName, source generators, and MVVM tools.