String Interpolation in C# with examples

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Last Updated : 01/09/2020

Posted By :- vikas_jk

If you are new to C# or have been learning C# string from quite some time, then you may stumble upon, string interpolated version in C# ($"Hello, {YourName}"), which was introduced in C# 6, so in this article, I have explained about c# string interpolated version with console application examples.

What is string interpolation?

In Programming language, string interpolation, is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values.

So we can say, an interpolated string is a string literal that might contain interpolation expressions. When an interpolated string is resolved to a result string, items with interpolation expressions are replaced by the string representations of the expression results.

Available in C# 6.0 and later, Interpolated strings are identiified by $ special character, take a look at an example

 class Program
    {
        static void Main(string[] args)
        {
            var name = "Vikas Lalwani";
            Console.WriteLine($"My name is {name}");
            Console.ReadKey();
        }
    }

Output of the above code will be

My name is Vikas Lalwani

Here is the image below which shows output, when code is written in Visual Studio using console application.

In C#, a string literal is an interpolated string, when you prepand it with the $ symbol. You cannot have any white space between the $ and the " that starts a string literal.

Interpolated String Example in C#

Let's take a look at more complex example of interpolated string, suppose, you want to ask the name and age from user, then show it as an output on console.

namespace StringInterpolation
{
    class Program
    {
        static void Main(string[] args)
        {
            string name="", age = "";

            Console.WriteLine("What is your name?");
            //assign value to name variable
            name=Console.ReadLine();

            Console.WriteLine("What is your age?");
            //assign value to age variable
            age = Console.ReadLine();

            //print it to console using interpolated string 
            Console.WriteLine($"Your name is {name} and age is {age}");

            Console.ReadKey();
        }
    }
}

Output:

What is your name?
John Kanhwald
What is your age?
20
Your name is John Kanhwald and age is 20

Adding Special characters inside interpolated string in C#

Suppose you want to add special characters like "; {" etc inside interpolated string, then you can do it like

string name = "John";
Console.WriteLine($"Hello, \"are you {name}?\", but not the terminator movie one :-{{");

Output:

Hello, "are you John?", but not the terminator movie one :-{

Expression Evaluation

With string interpolation, expressions within curly braces {} can also be evaluated. The result will be inserted at the corresponding location within the string.

let's take a look at an example

Console.WriteLine($"The greater one is: { Math.Max(10, 20) }");
Console.WriteLine($"Today's day and date is: {DateTime.Today:dddd, dd-MM-yyyy}");

Output:

The greater one is: 20
Today's day and date is: Tuesday, 01-09-2020

Method call

Yes, you can also call methods, let them evaluate and return results. The returned result will be placed in the corresponding location.

        static void Main(string[] args)
        {
            Console.WriteLine($"The 5*5  is {MultipleByItSelf(5)}");
        }
      
        static int MultipleByItSelf(int num)
        {
            //multiply number by itself and return result
            return num * num;
        }

Output: