如何使用Regex生成有效输入的示例？

Question

I want to generate an example of a valid input by Regex pattern. I'm programming with C# .Net . Like this:

//this emthod doesn't exists, its an example of funcionality that I want.
Regex.GenerateInputExample("^[0-9]{15}$"); 

So, this example gives-me a possible value, like 000000000000000 . How to do this?

Answer 1

So, this problem would take some time to solve, since the functionality is not built in. I'll give a general way to solve it:

Using an ascii (or unicode) chart find out the character codes that correspond to the characters you are using for your regex (65 =A, 69 = D, etc)

Create a random function with those bounds. Multiple bounds would take a little more trickery (AZ =26, 0-9 = 10, so a random number from 0- 35)

Random random = new Random();
int randomNumber = random.Next(65, 70); // this generates a random number including the bounds of 65-69)

char temp = (char)random;

Next you would take the randomly generated characters and add them together into a string.

        int lowerBound = 65, upperBound =69;
        int length = 6;
        char temp;
        int randomNumber;
        string result= "";

        Random rand = new Random();
        for (int a = 0; a <= length; a++)
        {
            randomNumber = rand.Next(lowerBound, upperBound);
            temp = (char)randomNumber;
            result = result + temp;
        }                  //result is the indirect regex generated string

Indirectly giving you a regex generated string.

The next step is parsing information out of a regex. I've provided a simple case below that will not work for every regex, due to regex complexity.

        Regex bob = new Regex("[A-Z]");

        int lowerBound = Convert.ToInt32(bob.ToString()[1]);
        int upperBound = Convert.ToInt32(bob.ToString()[3]);
        int length = 6; //length of the string to be generated
        char temp;
        int randomNumber;
        string result= "";

        Random rand = new Random();
        for (int a = 0; a <= length; a++)
        {
            randomNumber = rand.Next(lowerBound, upperBound);
            temp = (char)randomNumber;
            result = result + temp;
        }

( This process could be streamlined into class and utilized etc)