检查数据库中是否有空行C＃

Question

I have connected my codes (using visual studio C#) to my Microsoft Access database.. My application is able to add and remove user from the database. My database only allows two users (Administrator and user).

Lets say that the administrator has remove the user from the database... I would the application to redirect the user to a registration page after it has detected that there is only one user in the database. How can check for that using my code?

I have already added an SQL statement to my codes, can i add another? how can i check for null column?

Answer 1

private void Login_Load(object sender, EventArgs e)
{      
    // you can here add validation 
    //by using this sql: select count(*) from [User]


      LoginUsernameTextBox.Focus();
    }

i dont recommend using linq because it is not very flexible and working rather slow, you should learn how to write with ado in case you can face complex needs later. But you already done querying part and can use the method you wrote before so it will look like this:

User[] somethin = GetAllUsers();
if(somethin.Count==1){
//now you have one user record in your database
}