Create (Generate) custom 8 digit Random Number using C# and VB.Net in ASP.Net

Hi naresh1994,

Check this example. Now please take its reference and correct your code.

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    Response.Write(GenerateCustomRandomString());
}

private string GenerateCustomRandomString()
{
    string acceptedCharachers = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string acceptedNumbers = "0123456789";
    string firstString = GenerateRandomString(acceptedCharachers, 2);
    string firstNumber = GenerateRandomString(acceptedNumbers, 1);
    string secondString = GenerateRandomString(acceptedCharachers, 3);
    string secondNumber = GenerateRandomString(acceptedNumbers, 1);
    string thirdString = GenerateRandomString(acceptedCharachers, 1);

    return firstString + firstNumber + secondString + secondNumber + thirdString;
}

private string GenerateRandomString(string acceptedCharachersOrNumbers, int length)
{
    Random random = new Random();
    return new string(Enumerable.Repeat(acceptedCharachersOrNumbers, length)
                                .Select(x => x[random.Next(x.Length)]).ToArray());
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Response.Write(GenerateCustomRandomString())
End Sub

Private Function GenerateCustomRandomString() As String
    Dim acceptedCharachers As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    Dim acceptedNumbers As String = "0123456789"
    Dim firstString As String = GenerateRandomString(acceptedCharachers, 2)
    Dim firstNumber As String = GenerateRandomString(acceptedNumbers, 1)
    Dim secondString As String = GenerateRandomString(acceptedCharachers, 3)
    Dim secondNumber As String = GenerateRandomString(acceptedNumbers, 1)
    Dim thirdString As String = GenerateRandomString(acceptedCharachers, 1)
    Return firstString & firstNumber & secondString & secondNumber & thirdString
End Function

Private Function GenerateRandomString(ByVal acceptedCharachersOrNumbers As String, ByVal length As Integer) As String
    Dim random As Random = New Random()
    Return New String(Enumerable.Repeat(acceptedCharachersOrNumbers, length) _
                                .Select(Function(x) x(random.Next(x.Length))).ToArray())
End Function

Screenshot