如何添加{in String Format c#

string str1 = "Hello";
string str2 = "World";
string result = str1 + " " + str2;
Console.WriteLine(result);  // 输出：Hello World

string str1 = "Hello";
string str2 = "World";
string result = string.Concat(str1, " ", str2);
Console.WriteLine(result);  // 输出：Hello World

string name = "Alice";
int age = 25;
string message = $"My name is {name} and I'm {age} years old.";
Console.WriteLine(message);  // 输出：My name is Alice and I'm 25 years old.

string name = "Alice";
int age = 25;
string message = string.Format("My name is {0} and I'm {1} years old.", name, age);
Console.WriteLine(message);  // 输出：My name is Alice and I'm 25 years old.