[C#]初心者のための文字列操作ガイド！基本的な記述を一気に紹介する

string greeting = "Hello, C#!"; 
string emptyString = String.Empty;

string firstName = "John";
string lastName = "Doe";
string fullName = firstName + " " + lastName;
// または
string concatenatedName = String.Concat(firstName, " ", lastName);

string exampleString = "C# is powerful!"; 
int length = exampleString.Length;

char firstChar = exampleString[0]; 
string replacedString = exampleString.Replace('C', 'A');

 string originalString = "   こんにちは、\n　世界！   ";
// Trimメソッドを使用して空白と改行を削除
string trimmedString = originalString.Trim();

string inputString = "Hello, World!";
int charactersToRemove = 5; // 削除する文字数
string resultString = inputString.Substring(0, inputString.Length - charactersToRemove);

string originalString = "Hello, World!";
string replacement = "Universe";
int startIndex = 7; // 置換を開始する位置

string modifiedString = originalString.Substring(0, startIndex) + replacement + originalString.Substring(startIndex + replacement.Length);

string str1 = "Hello"; 
string str2 = "Hello";
if (str1 == str2) { // 文字列が等しい場合の処理 }

string str1 = "Hello";
string str2 = "hello";

// 大文字小文字を区別せずに比較
bool result = str1.Equals(str2, StringComparison.OrdinalIgnoreCase);

string inputString = "1234";

if (Regex.IsMatch(inputString, @"^\d{4}$"))
{
 　 Console.WriteLine("入力された文字列は4桁の数字です。");
}

string csvData = "apple,orange,banana"; 
string[] fruits = csvData.Split(',');

string input = "apple,banana,orange"; 
char delimiter = ','; 
string[] elements = input.Split(delimiter);

string originalString = "Hello, こんにちは"; 
int byteCountToCut = 10; 
byte[] bytes = Encoding.UTF8.GetBytes(originalString); 
string cutString = Encoding.UTF8.GetString(bytes, 0, byteCountToCut);

string upperCaseString = exampleString.ToUpper(); 
string lowerCaseString = exampleString.ToLower();

string text = "42";
int result = int.Parse(text);

string dateString = "2023-12-31";
DateTime resultDate;

if (DateTime.TryParse(dateString, out resultDate))
{
    Console.WriteLine("変換成功：" + resultDate);
}
else
{
    Console.WriteLine("変換失敗");
}

int age = 25; 
string formattedString = String.Format("I am {0} years old.", age); 
// または 
string interpolatedString = $"I am {age} years old.";