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How to Generate Random OTP(One Time Passsword) in ASP.NET using C#

Here I will explain how to generate random one time password or otp in asp.net using c#.
In this we will generate otp using capital and small letters and numbers.

Default.aspx :

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Generate Random OTP in Asp.net(C#),Asp.net using C#</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="BtnGenerateOTP" Text="Generate" runat="server"           OnClick="BtnGenerateOTP_Click" /><br />
        <asp:Label ID="lblDisplayOTP" runat="server" />
    </div>
    </form>
</body>
</html>

Default.aspx.cs

  protected void BtnGenerateOTP_Click(object sender, EventArgs e)
 {
            // declare array string to generate random string with combination of small,capital letters and numbers
            char[] charArray = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
            string strrandom = string.Empty;
            Random objrandom = new Random();
            int noofcharacters = 7;//change OTP length as per your requirment like 1,2,3,4,5,6
            for (int i = 0; i < noofcharacters; i++)
            {
                //It will not allow Repetation of Characters
                int pos = objrandom.Next(1, charArray.Length);
                if (!strrandom.Contains(charArray.GetValue(pos).ToString()))
                    strrandom += charArray.GetValue(pos);
                else
                    i--;
            }
            lblDisplayOTP.Text = strrandom;
   }
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