NullReferenceException was unhandled - How to resolve it
<p>Here is my code:</p>

<pre><code>private void button1_Click(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection("Data Source=MANINOTEBOOK\\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=Casesheet");
    con.Open();
    SqlCommand cmd = new SqlCommand("select PatientID from FTR where PatientID='" + textBox1.Text + "'", con);
    textBox2.Text = cmd.ExecuteScalar().ToString();
    if (textBox2.Text == textBox1.Text)
    {
        Consultation cs = new Consultation(textBox1.Text);
        cs.Show();
    }
    else
    {
        MessageBox.Show("Data not found");
    }            
}
</code></pre>

<p>When i compile this code i get an error "NullReferenceException was unhandled". I dont know how to resolve it. I need to check the value generated in the "execute scalar" command is null or not.  Kindly help me in resolving this problem.</p>
