Check If String Is All Uppercase Or All Lowercase in C# — Use ToUpper/ToLower, Char Checks & Null...

Описание: 🎥 Check All Uppercase or Lowercase in C#
In this video, you’ll learn how to determine whether a string is entirely uppercase or entirely lowercase in C#. We’ll explore built-in methods (ToUpper, ToLower, StartsWith/EndsWith won’t help here), character-wise checks, LINQ approaches, and culture-aware options. You’ll also see defensive handling for null, empty, and non-letter characters so your code behaves predictably with real user input.
________________________________________
Key Learning Points:
• Normalize and compare (str == str.ToUpper() / str == str.ToLower()) and when that’s sufficient
• Use char checks (char.IsLetter) and LINQ (All) to ignore non-letter characters if needed
• Handle culture differences with ToUpperInvariant() / ToLowerInvariant() for consistent behavior
• Deal with null/empty strings and provide clear fallback or validation messages
• Write a reusable helper method that’s easy to unit-test and returns a clear enum/boolean result
________________________________________
What You’ll Need:
Basic C# knowledge — strings, LINQ (optional), and console or test harness to run examples. Visual Studio, VS Code, or any .NET-capable editor with the .NET SDK will work fine.
________________________________________
📚 Resources:
• String casing: ToUpper, ToLower, ToUpperInvariant, ToLowerInvariant
• char.IsLetter, LINQ All, and simple iteration patterns
• Defensive programming: null/empty checks and culture-aware comparisons
________________________________________
👍 Found this useful?
Give the video a like, paste tricky test strings in the comments, and subscribe for more practical C# string tutorials!