Create web interface for C# program

I have a working C# program, and I would like to build a web interface for it so that the program can be accessed via my website. About the C# program: -The program needs to be constantly running -- it establishes a connection, so I do not want a new instance of the program started up every time it is called from the webpage. -Program input is a single string. -Program output returns multiple lines of text retrieved from a server and currently outputs to console. What I want on the webpage interface: - User will input the string into a text box and hit "enter". The resulting webpage should then be generated containing all of the program output. I will provide more details on webpage formatting later on. - The interface should be able to handle multiple user requests. The program takes around 1 second to process each request. If you have additional questions, feel free to message me. Thanks