C# Discussion Boards - CodeProject

17-Sep-12 22:26

First of all, welcome to the world of programming. I hope that the negative votes won't put you off.

Unfortunately, you have a lot of work ahead of you getting to understand the basics of programming in .NET. This is far too big an area for you to skip, and no one is likely to offer to enter into correspondence with you to teach you how to do this. The brutal truth is that we are all busy people, and offering this level of tuition is a full time affair - saying that, there's no reason for you not to ask about specific things and people will try to help you here if they can.

I would suggest that you start off by reading something like Jon Skeet's C# in Depth[^] to get a good understanding of C#.

Finally - the API itself. Writing an API is hard. It's not simply a matter of slinging some methods together. A good API requires a deep understanding of how people are going to access your code, and how they are going to use it. This really is advanced stuff and I would steer clear of it if possible. If you must produce an API, make sure that you check every input to ensure that it is valid - the golden rule of API design is "trust nothing".

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Re: The API

Richard MacCutchan17-Sep-12 22:41

Richard MacCutchan

17-Sep-12 22:41

mauricemcse wrote:
create an API for a project.

My first question would be: why do you believe you need to create an API? Have you actually analysed the problem you are trying to solve and determined that this is the optimum answer, or do you just think it 'sounds right'?

As to learning, you don't mention what language(s) you plan to use, but since you posted this in the C# forum I would suggest .NET Book Zero[^] as an excellent primer.

One of these days I'm going to think of a really clever signature.

C# access a file

classy_dog17-Sep-12 8:37

classy_dog

17-Sep-12 8:37

In a C# 2008 desktiop application, I have a line of code that fails a try catch block.

The line of code is:

System.IO.FileStream fileStream = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);

The wholse section of code looks like:

  public Attachment AttIputDoc(String custId, String fileName)
        {

           Attachment att = new Attachment();
            byte[] buffer = null;
            try
System.IO.FileStream fileStream = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
catch (Exception e)
    {
    }

The line of code is trying to access a file that does not exist in a specific location.

Can you tell me how the code listed above knows where the directory path is for the file that needs to get uploaded at? The place it thinks the file needs to be loaded from is where the source code of where the application is acutally running from.

How would I override the default location so I can obtain the value from the app.config file?

Pete O'Hanlon17-Sep-12 9:01

17-Sep-12 9:01

This supposes that you have stored the value in your appSettings in a key called Path.

string path = ConfigurationManager.AppSettings["path"];
string fullPath = System.IO.Path.Combine(path, fileName);

Then, use fullPath in place of fileName when you create the FileStream.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

classy_dog17-Sep-12 17:02

classy_dog

17-Sep-12 17:02

I obtained the code from a contract shop. You code has been setup in the app.config file yet.

Pete O'Hanlon17-Sep-12 22:05

17-Sep-12 22:05

If this method is sealed to you, then you must pass in the fully qualified file name. The code I gave you will still do.

This is the problem with contract shops; they don't always give you good code. They'll give you exactly, and only, what you ask for.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Internal connection fatal error!! why?!!

PIEBALDconsult17-Sep-12 17:00

PIEBALDconsult

17-Sep-12 17:00

But even when it works the reference will immediately go out of scope.

Jassim Rahma17-Sep-12 5:12

17-Sep-12 5:12

Hi,

I am getting the above error on the last line:

MSSQLconnection.Close();

could you please help..

here is the code:

try
{
    MSSQLconnection = new SqlConnection(ConfigurationManager.ConnectionStrings["MSSQL"].ConnectionString);
    MSSQLconnection.Open();

    // where is_migrated = false;
    MSSQLcommand = new SqlCommand("select * from persons where is_migrated = 0 order by file_no", MSSQLconnection);
    MSSQLreader = MSSQLcommand.ExecuteReader();

    while (MSSQLreader.Read())
    {
        // display the file no;
        lblFileNo.Text = "File# " + MSSQLreader["file_no"].ToString();

        // update MySQL 
        MySQL_connection = new MySqlConnection(ConfigurationManager.ConnectionStrings["mySQL"].ConnectionString);
        MySQL_connection.Open();
        // MySQL_command = new MySqlCommand("insert into patients (current_file_no, id_type, id_number, date_of_birth, full_name, nationality, gender, old_file_no, marital_status, blood_group, patient_is_vip, is_outside_country, address_outside_address, address_country, address_flat, address_building, address_road, address_avenue, address_block, address_po_box, contact_mobile, contact_home_tel, personal_email, created_date) values (?current_file_no, ?id_type, ?id_number, ?date_of_birth, ?full_name, ?nationality, ?gender, ?old_file_no, ?marital_status, ?blood_group, ?patient_is_vip, ?is_outside_country, ?address_outside_address, ?address_country, ?address_flat, ?address_building, ?address_road, ?address_avenue, ?address_block, ?address_po_box, ?contact_mobile, ?contact_home_tel, ?personal_email, ?created_date)", MySQL_connection);
        MySQL_command = new MySqlCommand("insert into patients (current_file_no, id_type, id_number, date_of_birth, full_name, nationality, gender, old_file_no, marital_status, blood_group, patient_is_vip, is_outside_country, address_outside_address, address_country, address_flat, address_building, address_road, address_avenue, address_block, address_po_box, contact_mobile, contact_home_tel, personal_email, created_date) values (param_current_file_no, param_id_type, param_id_number, param_date_of_birth, param_full_name, param_nationality, param_gender, param_old_file_no, param_marital_status, param_blood_group, param_patient_is_vip, param_is_outside_country, param_address_outside_address, param_address_country, param_address_flat, param_address_building, param_address_road, param_address_avenue, param_address_block, param_address_po_box, param_contact_mobile, param_contact_home_tel, param_personal_email, param_created_date)", MySQL_connection);

        MySQL_command.Parameters.Add("param_current_file_no", MySqlDbType.Int32).Value = Convert.ToInt32(MSSQLreader["file_no"]);
        MySQL_command.Parameters.Add("param_id_type", MySqlDbType.VarChar, 255).Value = MSSQLreader["id_type"].ToString();
        MySQL_command.Parameters.Add("param_id_number", MySqlDbType.VarChar, 255).Value = MSSQLreader["id_number"].ToString();
        MySQL_command.Parameters.Add("param_date_of_birth", MySqlDbType.VarChar, 255).Value = MSSQLreader["date_of_birth"];
        MySQL_command.Parameters.Add("param_full_name", MySqlDbType.VarChar, 255).Value = MSSQLreader["person_name"].ToString();
        MySQL_command.Parameters.Add("param_nationality", MySqlDbType.VarChar, 255).Value = MSSQLreader["nationality"].ToString();
        MySQL_command.Parameters.Add("param_gender", MySqlDbType.VarChar, 255).Value = MSSQLreader["gender"].ToString();
        MySQL_command.Parameters.Add("param_old_file_no", MySqlDbType.VarChar, 255).Value = MSSQLreader["old_file_no"].ToString();
        MySQL_command.Parameters.Add("param_marital_status", MySqlDbType.VarChar, 255).Value = MSSQLreader["marital_status"].ToString();
        MySQL_command.Parameters.Add("param_blood_group", MySqlDbType.VarChar, 255).Value = MSSQLreader["blood_group"].ToString();
        MySQL_command.Parameters.Add("param_patient_is_vip", MySqlDbType.VarChar, 255).Value = MSSQLreader["person_is_vip"].ToString();
        MySQL_command.Parameters.Add("param_is_outside_country", MySqlDbType.VarChar, 255).Value = MSSQLreader["is_outside_country"].ToString();
        MySQL_command.Parameters.Add("param_address_outside_address", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_outside_address"];
        MySQL_command.Parameters.Add("param_address_country", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_country"].ToString();
        MySQL_command.Parameters.Add("param_address_flat", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_flat"];
        MySQL_command.Parameters.Add("param_address_building", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_building"];
        MySQL_command.Parameters.Add("param_address_road", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_road"];
        MySQL_command.Parameters.Add("param_address_avenue", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_avenue"];
        MySQL_command.Parameters.Add("param_address_block", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_block"];
        MySQL_command.Parameters.Add("param_address_po_box", MySqlDbType.VarChar, 255).Value = MSSQLreader["address_po_box"];
        MySQL_command.Parameters.Add("param_contact_mobile", MySqlDbType.VarChar, 255).Value = MSSQLreader["contact_moblle"];
        MySQL_command.Parameters.Add("param_contact_home_tel", MySqlDbType.VarChar, 255).Value = MSSQLreader["contact_home_tel"];
        MySQL_command.Parameters.Add("param_personal_email", MySqlDbType.VarChar, 255).Value = MSSQLreader["email_address"];
        MySQL_command.Parameters.Add("param_created_date", MySqlDbType.Timestamp).Value = Convert.ToDateTime(MSSQLreader["created_date"]);

        int MySQL_reader = MySQL_command.ExecuteNonQuery();

        MySQL_command.Dispose();
        MySQL_connection.Close();

        // Mark it Updated in MSSQL
        mark_migrated(Convert.ToInt32(MSSQLreader["file_no"]));
    }
}
catch (Exception exp)
{
    return;
}
finally
{
    MSSQLcommand.Dispose();
    MSSQLreader.Close();
    MSSQLconnection.Close();
}

Pete O'Hanlon17-Sep-12 6:09

17-Sep-12 6:09

You have closed your connection in the body of the try block, and then you attempt to close it again in the finally block. You only need to do this once - the simple fix is to remove the Dispose/Close pair from inside the try part.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Andrei Straut17-Sep-12 6:14

Andrei Straut

17-Sep-12 6:14

The way I see it, he actually has 2 different connections in there OMG | :OMG:

an MS-SQL and a MySQL one, and in the try he closes the MySQL one, not the MS-SQL one. I had posted the same answer immediately after you, but deleted it. Then I took another look, and spotted it

EDIT: I did upvote your solution before that though, and I'll leave it as is

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Emmanuel Medina17-Sep-12 7:43

Emmanuel Medina

17-Sep-12 7:43

What Andrei says is true, I had thought what Pete said (closing the connection twice) but then I saw they're different connections.

I think I've seen this problem when the command's connection is not closed right away after use; since you already have the data in the reader, maybe you could close the SQLConnection before the while loop and see if it helps?.

And just my point of view: the catch block should either give an informative message of the problem (or at least just log the message somewhere) or it should be done away with.

Jassim Rahma17-Sep-12 7:56

17-Sep-12 7:56

Hi guys,

no he's right Smile | :)

sorry..

i missed it..

the connection was already closed here:

mark_migrated(Convert.ToInt32(MSSQLreader["file_no"]));

this is the code which closes the connection:

private void mark_migrated(int file_no)
{
    MSSQLconnection_Migrated = new SqlConnection(ConfigurationManager.ConnectionStrings["MSSQL"].ConnectionString);
    MSSQLconnection_Migrated.Open();

    // where is_migrated = false;
    MSSQLcommand_Migrated = new SqlCommand("update persons set is_migrated = 1 where file_no = " + file_no, MSSQLconnection_Migrated);
    int MSSQLreader_Migrated = MSSQLcommand_Migrated.ExecuteNonQuery();

    MSSQLcommand_Migrated.Dispose();
    MSSQLconnection_Migrated.Close();
}

I will try checking connection state before closing and revert back if not zsolved.

thanks guys

Emmanuel Medina17-Sep-12 8:12

Emmanuel Medina

17-Sep-12 8:12

jrahma wrote:
MSSQLconnection_Migrated = new SqlConnection(ConfigurationManager.ConnectionStrings["MSSQL"].ConnectionString);

Isn't that a whole different connection though?

Jassim Rahma17-Sep-12 8:18

17-Sep-12 8:18

oh sorry!

you are right..

then where is the problem?!!

Andrei Straut17-Sep-12 8:25

Andrei Straut

17-Sep-12 8:25

Scoping issues. Try moving your MSSQL connection before the try - catch block. Also, I've only now noticed it. Just out of curiosity: does your code even compile?

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PIEBALDconsult17-Sep-12 8:42

PIEBALDconsult

17-Sep-12 8:42

I don't think that's it either.

PIEBALDconsult17-Sep-12 8:39

PIEBALDconsult

17-Sep-12 8:39

I dunno.

Does your mark_migrated try to use the same Connection reference that the above code uses? Or does it replace it?

Unrelated to the error:

Please don't keep instantiating and disposing the Connection, Command, and Parameters within the while loop.

0) Instantiate the Connection
1) Instantiate the Command
2) Instantiate and Add the Parmeters
3) while (MSSQLreader.Read())
3.1) Assign the Parameter values
3.2) ExecuteNonQuery
4) Close and Dispose

jschell17-Sep-12 8:43

jschell

17-Sep-12 8:43

In general a bad idea all around.

If an exception occurs you do NOT know why it occurred.
It is possible that almost anything afer that point will cause another exception.

Thus your code should be structured like this.

try
{
  ...
  command.Dispose();
  connect.Close();
  // At this point ALL resources should be cleaned up for
  // a normal exit.
}
catch(Exception e)
{
   // Clean up resources for abnormal exit.

   // REPORT THE EXCEPTION!!!!!
   try
   {
     command.Dispose();
   }
   catch(Exception)
   {
     // Ignore it because we already have an exception
   }

   try
   {
     connection.Close();
   }
   catch(Exception)
   {
     // Ignore it because we already have an exception
   }

   // Repeat try/catch for all other resources.
 }  // End of first try

 // There is NO finally block.  All connection
 // resources were cleaned up by regular process flow or exception block.
 // finally could be used for resources that were NOT connection related.

Pete O'Hanlon17-Sep-12 9:33

17-Sep-12 9:33

Now that it's been pointed out that they are different connections (I completely missed that), I would refactor this. Rather than the pattern you are using here, I would look to use the using command. Also, if you pass in CommandBehavior.CloseConnection on your call to ExecuteDataReader, you will automatically close the ocnnection when you finish iterating over the data reader.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

Jassim Rahma17-Sep-12 9:59

17-Sep-12 9:59

but how can I use the CommandBehavior.CloseConnection with ExecuteNonQuery()?