const interpolated string example

app.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <Using Include="System.Console" Static="True"/>
  </ItemGroup>

</Project>

Program.cs

const string Bar = "Bar";
const string DoubleBar = $"{Bar}_{Bar}";

WriteLine(DoubleBar);

Produces the following output:

Bar_Bar