Error: Cannot insert the value NULL into column 'ID'
<p>I created a registration page and I have a table with a Primary key of ID,but I get this error:
<a href="https://i.stack.imgur.com/UYxlo.png" rel="nofollow noreferrer">enter image description here</a></p>

<blockquote>
  <p>Cannot insert the value NULL into column 'Id', table
  'D:\课程学习\动态网站设计\课程设计1\APP_DATA\REGISTRATION.MDF.dbo.Table'; column
  does not allow nulls. INSERT fails. The statement has been terminated.</p>
</blockquote>

<p>I am just started to learn C# and really don't know how to fix this problem.</p>

<p>This is my code.</p>

<pre><code>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;

public partial class Registration : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["RegistrationConnectionString"].ConnectionString);
            conn.Open();
            string chekuser = "select count(*) from [Table] where UserName='" + TextBoxUN.Text + "'";
            SqlCommand com = new SqlCommand(chekuser, conn);
            int temp = Convert.ToInt32(com.ExecuteScalar().ToString());
            if (temp == 1)
            {
                Response.Write("The username is exsist");
            }

            conn.Close();

        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        try
        {
            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["RegistrationConnectionString"].ConnectionString);
            conn.Open();
            string insertQuery = "insert into [Table] (UserName,Email,Password) values (@Uname,@email,@password);";
            SqlCommand com = new SqlCommand(insertQuery, conn);
            com.Parameters.AddWithValue("@Uname",TextBoxUN.Text);
            com.Parameters.AddWithValue("@email", TextBoxEmail.Text);
            com.Parameters.AddWithValue("@password", TextBoxPass.Text);

            com.ExecuteNonQuery();
            Response.Redirect("Manager.aspx");
            Response.Write("Your registration is successful!");


            conn.Close();
        }
        catch (Exception ex)
        {
            Response.Write("Error:"+ex.ToString());
        }




    }
}
</code></pre>