random number generation

Is it required to have alpha characters in it?...or just that it "can" include alphas?

Randomize each digit separately, and then concatenate them together. That will take care of the 8 digits constraint.

For each digit, generate a random value between 0 and 35 (inclusive). If the result is between 0 and 9, use that result as a value. If it is greater than 9, generate a character that has an ASCII/Unicode value that is 87+result.

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An easier way would be to generate a big random number, convert it to an hexadecimal value and use that value in a lowercase String that you truncate to 8 characters. The problem with that simpler approach is that the alphabetic characters would be limited form "a" to "f".

nothing is required... except the length = 8 ...it can be all numbers or all smaller case alphabets or mixed of both...

ex: abhfgteh
ex: 78634198
ex: 127df423

n.ToString("x8") will work as long as n is an int.
http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx explains hex format.

Or are you trying to generate random strings that contain a..z & 0..9?

Give this a shot:

var chars = "abcdefghijklmnopqrstuvwxyz0123456789";
var random = new Random();
var result = new string(
    Enumerable.Repeat(chars, 8)
              .Select(s => s[random.Next(s.Length)])
              .ToArray());

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Another simple example:

private Random R = new Random();

        private string GetValue(int length)
        {
            string output = "";
            string allowed = "0123456789abcdefghijklmnopqrstuvwxyz";
            for (int i = 1; i <= length; i++)
            {
                output = output + allowed.Substring(R.Next(allowed.Length), 1);
            }
            return output;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            label1.Text = GetValue(8);
        }

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Yet another:

static string GenerateRandomString()
{
    const string CHOICES = "abcdefghijklmnopqrstuvwxyz01234567890";
    StringBuilder result = new StringBuilder(8);
    Random r = new Random();

    while (result.Length != 8)
    {
        int index = Math.Abs((int)(r.NextDouble() * int.MaxValue) % CHOICES.Length);

        System.Threading.Thread.Sleep(5);
        result.Append(CHOICES[index]);
    }

    return result.ToString();
}

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@disrupt , @kaufmed ,

It worked...

one more ... can we still restrict.... the random number to contain at most three alphabets and  the remaining 5 as integers.... is it possible...

>> "nothing is required... except the length = 8 ...it can be all numbers or all smaller case alphabets or mixed of both..."

...becomes...

>> "can we still restrict.... the random number to contain at most three alphabets and  the remaining 5 as integers...."

What other restrictions will pop up next?

Tell us exactly what you want...in detail.

try this...

protected void Page_Load(object sender, EventArgs e)
        {


            Response.Write(GetStringGen());

        }

        public string GetStringGen()
        {
            StringBuilder builder = new StringBuilder();
            builder.Append(RandomString(4, true));
            builder.Append(RandomNumber(1000, 9999));
            return builder.ToString();
        }

        private int RandomNumber(int min, int max)
        {
            Random random = new Random();
            return random.Next(min, max);
        }

        private string RandomString(int size, bool lowerCase)
        {
            StringBuilder builder = new StringBuilder();
            Random random = new Random();
            char ch;
            for (int i = 0; i < size; i++)
            {
                ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));
                builder.Append(ch);
            }
            if (lowerCase)
                return builder.ToString().ToLower();
            return builder.ToString();
        }

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