Asp.net Registration Form, need email validation in C#

try this: 



SqlConnection con = new SqlConnection("Data Source=SARANYA-TS02\\SQLEXPRESS;Initial Catalog=ss;Integrated Security=True");
        string Sqlquery = "SELECT * FROM RegistrationForm where E-mail_Address=" + TextBox7.Text + "'";
       con.Open();       
       SqlCommand com = new SqlCommand(Sqlquery, con);
        SqlDataReader reader = com.ExecuteReader();
       
        try
        {
            if (!reader.Read())
            {
                SqlCommand cmd = new SqlCommand("insert into RegistrationForm values('" + TextBox1.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "','" + TextBox4.Text
            + "','" + TextBox5.Text + "','" + TextBox6.Text + "','" + TextBox7.Text + "','" + TextBox8.Text + "','" + RadioButtonList1.SelectedValue
            + "','" + TextBox12.Text + "','" + TextBox9.Text + "','" + TextBox10.Text
            + "','" + TextBox11.Text + "','" + DropDownList4.SelectedValue + "','" + DropDownList5.SelectedValue + "')", con);
           
                cmd.ExecuteNonQuery();
            }
            else
            {
                MessageBox.Show(" EmailId already exists");
            }
            reader.Close();
            con.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }