How do I convert user string into a mathematical equation?

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C#

Hi, I'm using c# and I want to convert the user input string into a Mathematical equation. So, when the user input a math equation I want to store it as
a code(or in a text file so the user can use the equation later on to
evaluate values).

Ex) Enter your equation:
user: y=3x+2
Enter a value: 1
y at x=1 is 5

I want a way to use user's equation to evaluate it at certain values, such as x=1,2,3
If you don't know the answer please direct me into the right path,

I appreciate your time

What I have tried:

static void Main(string[] args)
        {
            string function = "";
            double value = 0;

            Console.WriteLine("Enter your function: ");
            function = Console.ReadLine();
            Console.WriteLine("Enter your value: ");
            value = Convert.ToDouble(Console.ReadLine());

        }