Untitled

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.master"
            AutoEventWireup="true" CodeFile="Register.aspx.cs" Inherits="Register" %>

    <asp:Content ID="Content1" ContentPlaceHolderID="MainContent"
    Runat="Server">
        <head>
            <link href="Style/Register.css" rel="stylesheet" />
        </head>
    <body>
        <div class="login-page">
      <div class="form">
        <form class="register-form">
          <input id="username" type="text" placeholder="Username" Runat="Server"/>
          <input id="password" type="password" placeholder="Password" Runat="Server" />
          <input id="confirm" type="password" placeholder="Confirm password" Runat="Server"/>
          <input id="email" type="text" placeholder="Email address" Runat="Server"/>
          <input id="phone" type="text" placeholder="Phone Number" Runat="Server"/>
            <input id="name" type="text" placeholder="Name" Runat="Server"/>
          <button onclick="Button1_Click">create</button>
          <p class="message">Already registered? <a href="login.aspx">Sign In
            <asp:SqlDataSource ID="SqlDataSource1" runat="server"
            ConnectionString="<%$ ConnectionStrings:regisString %>"
            SelectCommand="SELECT * FROM [regis]">
            </asp:SqlDataSource>
              </a></p>
                </form>
        </div>
    </div>
    </body>
    </asp:Content>

using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Data.SqlClient;
    using System.Configuration;
    using System.Data;

    public partial class Register : System.Web.UI.Page
    {

        protected void Page_Load(object sender, EventArgs e)
        {
            if (IsPostBack)
            {
    SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["regisString"].ConnectionString);
        conn.Open();
        string checkuser = "select count(*) from Regis where username='" + username.Value + "'";
        SqlCommand cmd = new SqlCommand(checkuser, conn);
        int temp = Convert.ToInt32(cmd.ExecuteScalar().ToString());

        if (temp == 1)
        {
            Response.Write("Student Already Exist");
        }

        conn.Close();
    }

}
        protected void Button1_Click(object sender, EventArgs e)
{
    try
    {
    SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["RegisString"].ConnectionString);
        conn.Open();
        string insertQuery = "insert into Regis(username,password,email,phone)values (@username,@password,@email,@phone,@name)";
        SqlCommand cmd = new SqlCommand(insertQuery, conn);
        cmd.Parameters.AddWithValue("@username",username.Value);
        cmd.Parameters.AddWithValue("@password",password.Value);
        cmd.Parameters.AddWithValue("@email",email.Value);
        cmd.Parameters.AddWithValue("@phone",phone.Value);
        cmd.Parameters.AddWithValue("@phone", name.Value);

        cmd.ExecuteNonQuery();

        Response.Write("Student registeration Successfully!!!thank you");

        conn.Close();

    }
    catch (Exception ex)
    {
        Response.Write("error" + ex.ToString());
    }
}
    }