"IF" used within program.cs (open SQL database, read, if null, show Form2, else, show Form1)

Ivan

I am having a difficult time creating an if statement in my program.cs file.
What I want to do is, before the main form (say Form1) loads, I want the program to check to make sure there is, or is not any information within my SQL database Tabel1. If there is information load Form2. If not, load Form1. (Form2 collects information and saves it into SQL database). Form1 is the default form to load. The main form. However, form1 needs information from SQL database in order to load.
I have tried this several different ways.
1. Created a hidden form upon start up where the form upon load, searches out the SQL database and sees if there is information in there or now.
2. Made a method within Form1 to check to see if information is within SQL database. If not, Form2 would load.
3. Program.cs file that opens sql database and searches out to see if there is data within the database table. if null, do this, else, do that.

I havent gotten anything to work. Here is what I have in my program.cs file.

 

 
public void OpenDatabase()
{
try
{
sqlcon.Open();
}
catch (SqlException ex)
{
throw new Exception("Problem opening database");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
static SqlConnection sqlcon;
 
public void Main1()
{
sqlcon = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Program Files\\Microsoft SQL Server\\MSSQL10.SQLEXPRESS\\MSSQL\\DATA\\NewFPDB.mdf;Integrated Security=SSPI;User ID=FPDB_Admin;Password=123456;Persist Security Info=True;Connect Timeout=30;User Instance=False;");
SqlCommand command = new SqlCommand
("SELECT AirportID from Airports", sqlcon);
OpenDatabase();
// Get the data reader
SqlDataReader reader = command.ExecuteReader();
// Process each result
reader.Read();
 
if (reader != null)
{
MessageBox.Show("1");
Application.Run(new Form1());
sqlcon.Close();
}
else
{
Application.Run(new Form2());
sqlcon.Close();
}
 
reader.Close();
sqlcon.Close();
}
 
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
sqlcon = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Program Files\\Microsoft SQL Server\\MSSQL10.SQLEXPRESS\\MSSQL\\DATA\\NewFPDB.mdf;Integrated Security=SSPI;User ID=FPDB_Admin;Password=123456;Persist Security Info=True;Connect Timeout=30;User Instance=False;");

sqlcon.Open();

SqlCommand command = new SqlCommand
("SELECT UserID from Users", sqlcon);

// Get the data reader
SqlDataReader reader = command.ExecuteReader();
// Process each result
reader.Read();
 
if (reader != null)
{
//MessageBox.Show("1");
Application.Run(new Form1());
sqlcon.Close();
}
else
{
Application.Run(new Form2());
sqlcon.Close();
}
 
// Close the reader and the connection
reader.Close();
sqlcon.Close();
 
}

Can anyone please help me out and let me know where ive gone wrong. I am just tring to open up the database table, read it and if null, return form2. If data is present, load form1.

Thanks.
Ivan

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Ivan16y ago
Well, you must forgive my ignorance. :) Im two months into this (learning C#). Ive learned quite a bit, but definately realize that I need to learn much much more.
On that note, I appreciate your response and will take a look at it and your recommendations on research.
In the other programs I have, I do open the database in a seperate method and check to make sure that it is open or if there is a problem with it. Ive learned to do this much. :)
Thanks,
Ivan
0
Tim Claason16y ago
I personally have a lot of problems with this code, because it ignores fundamental rules of object oriented design, and multi-tiered design in general (your UI should talk to your business logic layer, and your business logic layer should talk to the data access layer).

Any direct interaction belongs in a separate class...something like

class DAL
{
SqlCommand command
SqlConnection sqlcon;
   public class OpenDatabaseConnection()
   {
      if(sqlcon == null)         sqlcon = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Program Files\\Microsoft SQL Server\\MSSQL10.SQLEXPRESS\\MSSQL\\DATA\\NewFPDB.mdf;Integrated Security=SSPI;User ID=FPDB_Admin;Password=123456;Persist Security Info=True;Connect Timeout=30;User Instance=False;");   }

   public string GetQueryResultsAsString(string query)
   {
      this.OpenDatabaseConnection();
      ///load command, get from the SQLDataReader, and put results into a string to return
   }
}

Then in your UI, you can simply instantiate the DAL

DAL _databaseAccessLayer = new DAL();

I'm sorry if this isn't helpful, but this code is a little bit offensive. For the new Form1() and new Form2(), check out how to use interfaces and the Factory design pattern. Also, check out building apps that separate the DAL (data access) from the BLL (business logic) from the UI (user interface).

Also, try to debug through it. In the C# IDE, you can put in break points, to see what the contents of the variables/objects are.

Have you ensured your connection string is correct, and that your SQLConnection state is open?
0