C#

Two warehouse bin counts got keyed into the wrong slots, and you need to flip them. To swap two numbers in C#, write (a, b) = (b, a); or use a temp variable. Both are safe, and the tuple version fits on one line: In this tutorial, I’ll compare every way to swap two numbers … Read more >>

Seven divided by two is 3 in C#, not 3.5. That surprise is why a C# program to add two numbers, then subtract, multiply and divide them, deserves more than one line. The core is simple: add with + and store the result. In this tutorial, I’ll start with a C# program to add two … Read more >>

To delete a folder in C#, call Directory.Delete(path, recursive: true). It removes the folder and every file and subfolder inside it. Drop the true and it only deletes an empty folder. In this tutorial, I’ll work through each C# delete folder case I’ve run into: empty and non-empty folders, missing paths, clearing a folder but … Read more >>

Log files pile up fast, and sooner or later your C# app has to clean them up. To delete a file in C#, call File.Delete(path) from System.IO. It removes the file and quietly does nothing if the file isn’t there. In this tutorial, I’ll build a small log-cleanup console tool step by step and cover … Read more >>

February 29, 2028 is the next leap day. A leap year program in C# needs one call, DateTime.IsLeapYear(year), or one expression: (year % 4 == 0 && year % 100 != 0) || year % 400 == 0. In this tutorial, I’ll show the built-in method, the manual leap year program in C# with if/else, … Read more >>

Nobody enjoys typing a long folder path. In a C# Windows Forms app, the folder browser dialog fixes that: create a FolderBrowserDialog, call ShowDialog(), and read SelectedPath when it returns DialogResult.OK. In this tutorial, I’ll put together a Report Exporter for a small Seattle accounting firm and use the folder browser dialog in C# three … Read more >>

Senior C# interviews in 2026 don’t ask you to define a class anymore. They hand you five lines of code and ask what it prints, then ask why. The C# interview questions for experienced developers below are the ones I keep seeing in US loops: type system traps, garbage collection, async/await, LINQ, modern C# 14 … Read more >>

Imagine a recruiter from a Dallas insurance company books your first .NET phone screen for Monday: 30 minutes, “mostly C# basics.” You’ve got one weekend. Most C# interview questions for freshers come from six areas: types, OOP, strings and collections, exceptions, LINQ and async basics, and modern C# features. Quick answer: learn the 40 questions … Read more >>

Need 1234567 to print as 1,234,567? To format a number with commas in C#, call number.ToString(“N0”) for whole numbers or ToString(“N2”) for two decimals, and pass an en-US culture so the separator doesn’t change from machine to machine. In this tutorial, I’ll cover each case I’ve hit in production code for C# format number with … Read more >>

Need to know if a name, email or code has a certain letter in it? In C#, text.Contains(‘M’) answers that in one call and returns true or false. In this tutorial, I’ll walk one customer name, Jenna Morales, through each C# string contains character check worth knowing on .NET 10: Output: ‘M’ is in “Jenna … Read more >>