How to fix invalid input in console application?

Question

Hello. I wrote a program, but it doesn't work correctly. How can I fix the error? The user must enter variable values ​​for the quadratic equation. Then follow the arrows down (up) to other variables. Is it possible to correct the situation so that the end of the line at ReadLine is indicated not through Enter, but through an arrow.

Only after the user enters all the values ​​he should press Enter.

I am attaching a link to the program and an example of how the program should work.

https://github.com/aminchikkk/ConsoleProgram/blob/main/PrintPoints.cs

Answer 1

Hi, vitaminchik

not through Enter, but through an arrow

I'm afraid Console.ReadLine can't achieve what you want.

If the standard input device is the keyboard, the ReadLine method blocks until the user presses the Enter key.
The ReadLine method executes synchronously. That is, it blocks until a line is read or the <kbd>Ctrl+Z</kbd> keyboard combination (followed by <kbd>Enter</kbd> on Windows), is pressed.

Update:

It is a possibility. Use readkey instead of Console.ReadLine(); to read individual characters and then concatenate them. Below is a quick test,and the code is not optimized.

        public static void Print()
        {
            origRow = Console.CursorTop;
            origCol = Console.CursorLeft;
            ConsoleKeyInfo ki;
            PrintMenu();
            WriteAt(5, selectedValue + 1);


            String temp = string.Empty;
           do
            {
                ki = Console.ReadKey();


                switch (ki.Key)
                {
                    case ConsoleKey.UpArrow:
                        {
                            variables[selectedValue] = temp;
                            introducedVariables[selectedValue] = variables[selectedValue];
                            if (selectedValue > 0)
                                selectedValue--;
                        }
                        temp = string.Empty;
                        break;
                    case ConsoleKey.DownArrow:
                        variables[selectedValue] = temp;
                        introducedVariables[selectedValue] = variables[selectedValue];
                        if (selectedValue < strings.Length - 1)
                        {
                            selectedValue++;
                        }
                        temp = string.Empty;
                        break;
                    case ConsoleKey.Enter:
                        variables[selectedValue] = temp;
                        introducedVariables[selectedValue] = variables[selectedValue];
                        break;
                    default:
                        {
                            temp += ki.KeyChar.ToString();
                        }
                        continue;
                }

                Console.Clear();
                PrintMenu();
                WriteAt(5, selectedValue + 1);
                


            }
            while (ki.Key != ConsoleKey.Enter) ;


            string line = new string('-', 50);
            Console.WriteLine(line);
        }

       protected static void WriteAt(int x, int y)
        {
            try
            {
                Console.SetCursorPosition(origCol + x, origRow + y);
 
            }
            catch (ArgumentOutOfRangeException e)
            {
                Console.Clear();
                Console.WriteLine(e.Message);
            }
        }

Best regards,

Minxin Yu

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