I am try to insert new user in database but exception throw

Question

SqlConnection sqlconnection = new SqlConnection("Data Source=(local);Initial Catalog=supermarket;Integrated Security=True");

SqlCommand sqlcom = new SqlCommand();

sqlcom.Connection = sqlconnection;

try

{

sqlconnection.Open();

if (radioButton1.Checked)

{

sqlcom.CommandText = "insert into CUSTOMERS values('" + textBox2.Text + "','" + textBox3.Text + "','" + textBox1.Text+ "','" + radioButton1.Text + "')";

sqlcom.ExecuteNonQuery();

sqlconnection.Close();

MessageBox.Show("Inserted successfully! ");

}

if(radioButton2.Checked)

{

sqlcom.CommandText = "INSERT INTO CUSTOMERS VALUES('" + textBox2.Text + "','" +textBox3.Text + "','" + textBox1.Text + "','" + radioButton2.Text + "')";

sqlcom.ExecuteNonQuery();

sqlconnection.Close();

MessageBox.Show("Inserted successfully! ");

}

}

catch (Exception)

{

MessageBox.Show("Error inserting Customer or Customer already exists!");

}

}