正在添加数据行，但我的表中没有数据，需要if语句来停止此操作吗？

Question

I am currently doing some work on a contact formular, I can make the text from my textboxes go into my coloumns, but if I dont type anything I dont want it to make a new row in the tabel with no data, which it is doing right now.

So I am guessing I need a if statement, but I dont know the syntax to make it.

This is my code:

    string Navn = TextBoxNavn.Text;
    string Emne = TextBoxEmne.Text;
    string Email = TextBoxEmne.Text;
    string Besked = TextBoxBesked.Text;

    SqlConnection conn = new SqlConnection

    (ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());

    SqlCommand cmd = new SqlCommand();
    cmd.Connection = conn;

    cmd.CommandText = "INSERT INTO Kontakt (Navn, Emne, Email, Besked) VALUES (@Navn, @Emne, @Email, @Besked)";
    cmd.Parameters.AddWithValue("@Navn", Navn);
    cmd.Parameters.AddWithValue("@Emne", Emne);
    cmd.Parameters.AddWithValue("@Email", Email);
    cmd.Parameters.AddWithValue("@Besked", Besked);

    conn.Open();
    cmd.ExecuteNonQuery();
    conn.Close();

Answer 1

Try this:

if(!string.IsNullOrEmpty(Navn) && !string.IsNullOrEmpty(Emne) && !string.IsNullOrEmpty(Email) && !string.IsNullOrEmpty(Besked))
{
    cmd.CommandText = "INSERT INTO Kontakt (Navn, Emne, Email, Besked) VALUES (@Navn, @Emne, @Email, @Besked)";
    cmd.Parameters.AddWithValue("@Navn", Navn);
    cmd.Parameters.AddWithValue("@Emne", Emne);
    cmd.Parameters.AddWithValue("@Email", Email);
    cmd.Parameters.AddWithValue("@Besked", Besked);

    conn.Open();
    cmd.ExecuteNonQuery();
    conn.Close();
}

Answer 2

There are many ways of doing this.

1.Make your columns in your database table mandatory(By setting "Not Null" property).

2.Add a validation in your code itself where your text boxes are mandatory.(Required field validator).

3.Here simply add this "if" condition

if(Navn !=null && Emne !=null && Email!=null && Besked !=null )
{
  //your code of insertion goes here.
}