检查字符“完整性”的好方法

Question

I'm working on making my own password generator; and I want it to create passwords that contain numbers, lowercase-letters, and uppercase-letters.

I am writing the program in C#, using Visual Studio.
Say I use the code below:

Random Rand = new Random();

Char C = Convert.ToChar(Rand.Next(0x30, 0x5A));

How could I make my program check whether (C) is equal to a number or a uppercase-letter?

Answer 1

Use Char.IsDigit (for decimal digits), or Char.IsNumber and Char.IsUpper .

These are all static methods defined on the Char structure.

---

An example, as requested:

if(Char.IsNumber(C))
{
  // Character is marked as a unicode number
}

Answer 2

you can check if:

int ordinal = (int)C;
if(( ordinal >= 65 && ordinal <= 90 ) || (ordinal >= 48 && ordinal <= 57))
{
Console.WriteLine( C + " is an uppercase A-Z or 0-9!" );
}

Answer 3

Probably just use Char.IsNumber and Char.IsUpper methods: see: http://msdn.microsoft.com/en-us/library/9s91f3by.aspx http://msdn.microsoft.com/en-us/library/yk2b3t2y.aspx

if (C.IsNumber || C.IsUpper) { // password code! }

(don't write your own password generator, unless it's just for fun though).

Answer 4

A better (and standard) way, is to create an 'alphabet' string of allowable characters and then generate a random index into the string, to select an allowable character.

Much better than first generating a random character and then checking if it is allowable.

"0123456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

Note the removed lowercase 'l' (looks like 1). You should remove any others such as zero versus 'O' possibly...or whatever your password rules allow)

Here's an example of using this technique to generate random strings:

public static class RandomUtils
{
    private static readonly Random random = new Random();

    public static string GenerateRandomAlphaNumericString(int length)
    {
        const string alpha = 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

        return GenerateRandomString(length, alpha);
    }

    public static string GenerateRandomString(int length, string alphabet)
    {
        int maxlen = alphabet.Length;

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < length; i++)
        {
            sb.Append(alphabet[random.Next(0, maxlen)]);
        }

        return sb.ToString();
    }
}