I’m a network guy, trying to evolve from scripts to GUI development.

But I’m facing this below for every example GPT suggests containing $ sign.

Examples like:

FtpWebRequest ftpRequest = (FtpWebRequest)WebRequest.Create($"{ftpServerUrl}");
or
textBox.Text = $"An error occurred: {ex.Message}";

Result into: Unexpected character ‘$’ (CS1056)

I circumvented by assigning the variable itself without any additional string.
It also works if I concatenate like:

textBox.Text = "An error occurred:" + ex.Message;

I’m using SharpDevelop with nothing else installed (no dotnet SDK).
I want to understand/know how to combine string with text using this $ sign for string interpolation like in the example provided by GPT.