$语法很好，但有一个缺点。

如果你需要一个字符串模板，在类级别上声明为field…它本该在一个地方。

然后你必须在同一层次上声明变量…这一点都不酷。

使用字符串要好得多。这类事情的格式语法

class Example1_StringFormat {
 string template = $"{0} - {1}";

 public string FormatExample1() {
   string some1 = "someone";
   return string.Format(template, some1, "inplacesomethingelse");
 }

 public string FormatExample2() {
   string some2 = "someoneelse";
   string thing2 = "somethingelse";
   return string.Format(template, some2, thing2);
 }
}

全局变量的使用并不是很好，除此之外，它也不适用于全局变量

 static class Example2_Format {
 //must have declaration in same scope
 static string some = "";
 static string thing = "";
 static string template = $"{some} - {thing}";

//This returns " - " and not "someone - something" as you would maybe 
//expect
 public static string FormatExample1() {
   some = "someone";
   thing = "something";
   return template;
 }

//This returns " - " and not "someoneelse- somethingelse" as you would 
//maybe expect
 public static string FormatExample2() {
   some = "someoneelse";
   thing = "somethingelse";
   return template;
 }
}

我不知道它是如何工作的，但你也可以用它来标记你的值!

例子:

Console.WriteLine($"I can tab like {"this !", 5}.");

当然，您可以将“this !”替换为任何变量或任何有意义的内容，就像您也可以更改选项卡一样。

注意，你也可以将两者结合起来，这很酷(尽管看起来有点奇怪):

// simple interpolated verbatim string
WriteLine($@"Path ""C:\Windows\{file}"" not found.");

下面的示例强调了使用插值字符串相对于string.Format()在简洁和可读性方面的各种优点。它还显示{}内的代码像任何其他函数参数一样被求值，就像调用string.Format()一样。

using System;

public class Example
{
   public static void Main()
   {
      var name = "Horace";
      var age = 34;
      // replaces {name} with the value of name, "Horace"
      var s1 = $"He asked, \"Is your name {name}?\", but didn't wait for a reply.";
      Console.WriteLine(s1);

      // as age is an integer, we can use ":D3" to denote that
      // it should have leading zeroes and be 3 characters long
      // see https://learn.microsoft.com/en-us/dotnet/standard/base-types/how-to-pad-a-number-with-leading-zeros
      //
      // (age == 1 ? "" : "s") uses the ternary operator to 
      // decide the value used in the placeholder, the same 
      // as if it had been placed as an argument of string.Format
      //
      // finally, it shows that you can actually have quoted strings within strings
      // e.g. $"outer { "inner" } string"
      var s2 = $"{name} is {age:D3} year{(age == 1 ? "" : "s")} old.";
      Console.WriteLine(s2); 
   }
}
// The example displays the following output:
//       He asked, "Is your name Horace?", but didn't wait for a reply.
//       Horace is 034 years old.

它创建了一个插值字符串。

从MSDN

用于构造字符串。插值字符串表达式看起来 比如包含表达式的模板字符串。一个插值 字符串表达式通过替换包含的字符串来创建字符串 表达式的ToString表示 结果。

ex :

 var name = "Sam";
 var msg = $"hello, {name}";

 Console.WriteLine(msg); // hello, Sam

可以在插值字符串中使用表达式

 var msg = $"hello, {name.ToLower()}";
 Console.WriteLine(msg); // hello, sam

它的好处是，您不需要像使用String.Format那样担心参数的顺序。

  var s = String.Format("{0},{1},{2}...{88}",p0,p1,..,p88);

现在如果你想移除一些参数你必须去更新所有的计数，现在不是这样了。

请注意，好的旧字符串。如果您想在格式中指定文化信息，格式仍然是相关的。

示例代码

public class Person {
    public String firstName { get; set; }
    public String lastName { get; set; }
}

// Instantiate Person
var person = new Person { firstName = "Albert", lastName = "Einstein" };

// We can print fullname of the above person as follows
Console.WriteLine("Full-Name - " + person.firstName + " " + person.lastName);
Console.WriteLine("Full-Name - {0} {1}", person.firstName, person.lastName);
Console.WriteLine($"Full-Name - {person.firstName} {person.lastName}");

输出

Full-Name - Albert Einstein
Full-Name - Albert Einstein
Full-Name - Albert Einstein

它是插值字符串。可以在任何可以使用字符串字面量的地方使用插值字符串。当运行您的程序将使用插值字符串文字执行代码时，代码将通过计算插值表达式计算一个新的字符串文字。每次执行带有插值字符串的代码时都会进行此计算。

以下示例生成一个字符串值，其中所有字符串插值值都已计算完毕。它是最终结果，类型为string。所有出现的双大括号(“{{”和“}}”)都被转换为单个大括号。

string text = "World";
var message = $"Hello, {text}";

执行以上2行后，变量message包含“Hello, World”。

Console.WriteLine(message); // Prints Hello, World

参考资料- MSDN