Passing parameters to a string interpolation handler constructor in C#

Annotate the argument receiving the interpolated string handler with the attribute InterpolatedStringHandlerArgument, for example:

public void PrintMessage(
    string color,
    [InterpolatedStringHandlerArgument("", "color")]
    ColorInterpolatedStringHandler builder
  )

Remarks:

• "" parameter refers to this in that context.
• "color" parameter refers to the argument named color.
  • The constructor of ColorInterpolatedStringHandler must receive both parameters: e.g. ctor(int literalLength, int formatCount, MyClass my, string color)

Know more:

• Creating a custom string interpolation handler in C#

References:

• Explore string interpolation handlers - C# | Microsoft Learn