When Random a string set how to avoid same char appear? thank you

Below is my code for create password which Including numbers and Letters and Password length is 6 chars.

public class PwCreator
	{
		public string Creator( )
		{
			String Vchar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
			String[] VcArray = Vchar.Split(',');
			String VNum = "";
			Random random = new Random();
			for (int i = 1; i <= 6; i++)
			{
				int iNum = 0;
				while ((iNum = Convert.ToInt32(VcArray.Length * random.NextDouble())) == VcArray.Length)
				{
					iNum = Convert.ToInt32(VcArray.Length * random.NextDouble());
				}
				VNum += VcArray[iNum];
			}
			return VNum;
 

		}
	}

the password Must mixed numbers and letters and can't have same char

when I test this code the problem is sometimes password is numbers or letters only ... just can't find out how to modify it can you please help?

and also.. how to avoid a same numbers or same letters appear in password?

thank you

Re: When Random a string set how to avoid same char appear? thank you

Hi,

Based on your description, you want the password is made up of numbers and letters which cann't contain the duplicate charactor.

There is code as below can achieve this. You can call it via GeneratePassword(6, 1). The variable numberOfNumeral means the minimal number of numerals and you can set it as 1 in order to make sure it contains number.

string GeneratePassword(int length, int numberOfNumeral)
    {
        if (((length < 1) || (length > 128)))
        {
            throw new ArgumentException("Membership_password_length_incorrect");
        }


        if ( (numberOfNumeral > length) || (numberOfNumeral < 0) )
        {
            throw new ArgumentException("Membership_min_required_non_alphanumeric_characters_incorrect");
        }


        int i;
        byte[] buffer1 = new byte[length];
        //chPassword contains the password's characters as it's built up
        char[] chPassword = new char[length];
        char[] chCharact = "ABCDEFGHIJKLMNOPQRSTUWXYZ1234567890".ToCharArray();
        char[] chNumeral = "1234567890".ToCharArray();


        Random rndNumber = new Random();
        for (i = 0; i < numberOfNumeral; i++)
        {
            int passwordPos;
            do
            {
                passwordPos = rndNumber.Next(0, length);
            }
            while ((int)chPassword[passwordPos] != 0);
            char chtem=chNumeral[rndNumber.Next(0, chNumeral.Length)];
            if (CharExist(chtem, chPassword))
                i--;
            else
                chPassword[passwordPos] = chtem;
        }




        for (i = 0; i < length; i++)
        {
            if ((int)chPassword[i] == 0)
            {
                char chtem = chCharact[rndNumber.Next(0, chCharact.Length)];
                if (CharExist(chtem, chPassword))
                    i--;
                else
                    chPassword[i] = chtem;


            }
        }
        return new string(chPassword);


    }


    private bool CharExist(char ch, char[] chs)
    {
        for (int i = 0; i < chs.Length; i++)
        {
            if (chs[i] == ch)
                return true;
        }
        return false;


    }

Hope this can help.