title: Error: Cannot insert the value NULL into column 'ID'
body: <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>