问如何添加if else语句以检查数据是否已输入SQL Server数据库并显示消息

EN

public partial class Form1 : Form
{
    SqlConnection con = new SqlConnection("Data Source=LAPTOP\\SQLEXPRESS02;Initial Catalog=Greenwich_Butcher;Integrated Security=True");

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {


        string dat = "Insert into [CustomerDetails](CustomerID, CustomerName, CustomerAddress, CustomerAddedDate) Values('" + Convert.ToInt32(textBox1.Text) + "','" + textBox2.Text + "','" + textBox3.Text + "','" + Convert.ToString(dateTimePicker1.Text) + "')";
        SqlCommand com = new SqlCommand(dat, con);
        con.Open();
        int rowsAffected = com.ExecuteNonQuery();
        if (rowsAffected > 0)
        {

            MessageBox.Show("Record inserted succesfully");
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
            dateTimePicker1.Text = "";
        }
        else
        {
            MessageBox.Show("Record not inserted succesfully");
        }
        con.Close();

    }
    private void button2_Click(object sender, EventArgs e)
    {
        Application.Exit();
    }
}