Write other C# code in an interpolated string?

In C# 11 we can now include newlines in an interpolated string. So we can write code like this:

    string pageTitle = "";
    string header = $"Header: {
      pageTitle switch
      {
        "" => "No title",
        _ => pageTitle
      }}";

Is there a way to write other code here beyond the switch statement?

I tried an if and it tells me that if is an invalid expression term.

    string header51 = $"Header: {
      if (pageTitle5 == "")
      {
        "No title";
      }
      else
      {
        pageTitle5;
      }  
    }";

Are there other statements beyond switch that work here?

Every expression will work. In C#, if is not an expression, but a statement.

However, the ternary operator yields an expression:

string header51 = $"Header: {
  (pageTitle5 == "" 
      ? "No title"
      : pageTitle5)
  }";

switch works in your example, because you do not use the switch statement but a switch expression.

If you prefer using if else statement, you can write the code like this :

    string header51 = $"Header:{() =>
	{
        if (pageTitle5 == "")
        {
            return "No title";
        }
        else
        {
            return pageTitle5;
        }  
    }
    }";

This way you have more flexibility to do extra logics in the if else block