without any repeat random number

If you need an algorithm for avoiding repetition of random numbers, then may have a look at my tip: "Random extraction of 5 cards from a deck"[^] (it's C++ code but heavily commented).
:-)

Follow the steps.

Step 1. Create method VerifyInDB(string/int randomvariable) in you cs file as follows

 public bool VerifyInDB(string/int RandomVariable)
{
bool b_RandomStatus=false;
sqlconnection con_SQLConnectionString=new sqlConnection(Constr);
SqlDataAdapter da_ForCheckforRandomInDB=new  SqlDataAdapter("select * from DB..tbl_table where RandomColumnName="+ randomvariable, con_SQLConnectionString);

DataTable dt_ForCheckforRandomInDB=new DataTable()
da.fill(dt_ForCheckforRandomInDB)
if(dt_ForCheckforRandomInDB.Rows.Count()>0)
	{
		b_RandomStatus=true;

	}
return b_RandomStatus;

}

Step 2. Create another method in the same *.cs file as follows

 public string/int CreateRandomNumber()
{
        //Assign random value here
	string/int RandomVariable ;//=Random();
	if(VerifyInDB(RandomVariable))
		{
                  //Random value Present in DB Call CreateRandomNumber() again
			CreateRandomNumber()
		}	

Return RandomVariable;

}

Step 3: Call CreateRandomNumber() any where in your code this will return random value which is not present in your DataBase.

Step 4:int/String RandumValue=CreateRandomNumber(); you will get the random value which is not repeated in DataBase.

To get a random number between x and y - http://www.whypad.com/posts/csharp-get-a-random-number-between-x-and-y/412/[^].

Random rnd = new Random();
protected int GetRandomInt(int min, int max)
{
    return rnd.Next(min,max);
}
int myInt = GetRandomInt(5, 1000); //gives in random integer between 5 & 1000

May this code help you....

public Random r = new Random();
List<string> l = new List<string>();

private void ButtonClick(object sender, EventArgs e)
{
    int temp = r.Next(1, 10);
    temp = RandomNumber(l, temp.ToString());
    listBox1.Items.Add(temp);
}
private int RandomNumber(List<string> listArray, string searchString)
{
    int temp;
    if (listArray.Count > 0)
    {
        re_View:
        bool isExists=l.Exists(delegate(string p){return p.Trim()==searchString;});
        if (isExists)
        {
             temp = r.Next(1, 10);
             searchString = temp.ToString();
             goto re_View;
        }
        else
        {
             l.Add(searchString);
             return Convert.ToInt32(searchString);
        }
    }
    l.Add(searchString);
    return Convert.ToInt32(searchString);
}