Generate multiple unique Random Number in ASP.Net using C# and VB.Net

Hi gmrneeraj,

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

HTML

<asp:TextBox runat="server" ID="TextBox1" /><br />
<asp:TextBox runat="server" ID="TextBox2" /><br />
<asp:TextBox runat="server" ID="TextBox3" /><br />
<asp:TextBox runat="server" ID="TextBox4" /><br />
<asp:TextBox runat="server" ID="TextBox5" /><br />
<asp:TextBox runat="server" ID="TextBox6" /><br />

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    List<string> numbers = new List<string>();
    for (int i = 0; i < 6; i++)
    {
        numbers.Add(GenerateID());
    }
    TextBox1.Text = numbers[0];
    TextBox2.Text = numbers[1];
    TextBox3.Text = numbers[2];
    TextBox4.Text = numbers[3];
    TextBox5.Text = numbers[4];
    TextBox6.Text = numbers[5];
}

protected string GenerateID()
{
    string alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string small_alphabets = "abcdefghijklmnopqrstuvwxyz";
    string numbers = "1234567890";

    string characters = alphabets + small_alphabets + numbers;
    int length = 6;
    string id = string.Empty;
    for (int i = 0; i < length; i++)
    {
        string character = string.Empty;
        do
        {
            int index = new Random().Next(0, characters.Length);
            character = characters.ToCharArray()[index].ToString();
        } while (id.IndexOf(character) != -1);
        id += character;
    }

    return id;
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim numbers As List(Of String) = New List(Of String)()
    For i As Integer = 0 To 5 Step 1
        numbers.Add(GenerateID())
    Next
    TextBox1.Text = numbers(0)
    TextBox2.Text = numbers(1)
    TextBox3.Text = numbers(2)
    TextBox4.Text = numbers(3)
    TextBox5.Text = numbers(4)
    TextBox6.Text = numbers(5)
End Sub

Protected Function GenerateID() As String
    Dim alphabets As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    Dim small_alphabets As String = "abcdefghijklmnopqrstuvwxyz"
    Dim numbers As String = "1234567890"
    Dim characters As String = alphabets & small_alphabets & numbers
    Dim length As Integer = 6
    Dim id As String = String.Empty
    For i As Integer = 0 To length - 1
        Dim character As String = String.Empty
        Do
            Dim index As Integer = New Random().Next(0, characters.Length)
            character = characters.ToCharArray()(index).ToString()
        Loop While id.IndexOf(character) <> -1
        id += character
    Next

    Return id
End Function