How to Generate One Time Password (OTP) in Asp.net Using C#

To Generate Random OTP  in Asp.net Open Your aspx Page and Write the Following Code

<center>

    <div>

Enter Number of Characters: <asp:TextBox ID="TxtCharacters" runat="server"/>

<asp:Button ID="BtnGenerateChar" Text="Generate" runat="server"

            onclick="BtnGenerateChar_Click" /><br />

<asp:Label ID="lblresult" runat="server" ForeColor="Blue" />

</div>

</center>

Now Add following Namespaces in Code behind

using System;

using System.Web;

After Completion of Adding Namespaces You Need to Write the Code like as Shown below

    protected void Page_Load(object sender, EventArgs e)

    {

    }

    protected void BtnGenerateChar_Click(object sender, EventArgs e)

    {

        // Declare Array string to Generate Random string with Combination of Small,Capital letters Numbers and Special Characters

        char[] charArr = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@#$%&".ToCharArray();

        string stringRandom = string.Empty;

        Random objran = new Random();

        int noofcharacters = Convert.ToInt32(TxtCharacters.Text);

        for (int i = 0; i < noofcharacters; i++)

        {

            //It will not allow Repetation of Characters

            int pos = objran.Next(1, charArr.Length);

            if (!stringRandom.Contains(charArr.GetValue(pos).ToString()))

                stringRandom += charArr.GetValue(pos);

            else

                i--;

        }

        lblresult.Text = stringRandom;

    }

DEMO