Introduction
C# string interpolation is a method of concatenating, formatting, and manipulating strings. This feature was introduced in C# 6. Using string interpolation, we can use objects and expressions as a part of the string interpolation operation.
Syntax of string interpolation starts with a ‘$’ symbol, and expressions are defined within a bracket {} using the following syntax.
{<interpolatedExpression>[,<alignment>][:<formatString>]}
Where
- interpolatedExpression - The expression that produces a result to be formatted
- alignment - The constant expression whose value defines the minimum number of characters in the string representation of the result of the interpolated expression. If positive, the string representation is right-aligned; if negative, it's left-aligned.
- formatString - A format string that is supported by the type of the expression result.
The following code example in Listing 1 concatenates a string where an object, the author, is a part of the string interpolation.
string author = "Mahesh Chand";
string hello = $"Hello {author} !";
Console.WriteLine(hello);
Listing 1.
The output of Listing 1 looks like Figure 1.
![String Interpolation]()
Figure 1.
The following code example in Listing 2 creates a string by concatenating values of four different types of variables.
// Simple String Interpolation
string author = "Mahesh Chand";
string book = "Programming C#";
int year = 2018;
decimal price = 45.95m;
string hello = $"{author} is an author of {book} . \n" +
$"The book price is ${price} and was published in year {year}. ";
Console.WriteLine(hello);
Listing 2.
The output of Listing 2 looks like Figure 2.
![]()
Figure 2.
The following code example in Listing 3 creates a string with spacing and adds 20 characters after the first object.
// Use spacing - add 20 chars
Console.WriteLine($"{author}{book, 20}");
Listing 3.
The following code example in Listing 4 uses an expression in a string interpolation operation.
// Use an expression
Console.WriteLine($"Book {book} price is {(price < 50 ? "50" : "45")} .");
Listing 4.
Learn more about string concatenation here: 6 Effective Ways to Concatenate Strings in C#.