C# Discussion Boards - CodeProject

30-Nov-09 7:09

Hello. Until now I always used conversion through Convert class. Example:

Int32 nInt = Convert.ToInt32("12345");

With that above I always used Try Catch to handle incorrect conversion. Lately I saw there can be achieved by using Int32.TryParse().

So which approach should be better, and what are good and cons of each method?

Thanks in Advance

PIEBALDconsult30-Nov-09 7:37

30-Nov-09 7:37

Don't use Convert when other options exist. Convert's methods generally just call the other methods anyway -- like Parse.

TryParse is generally better than Parse when available.

Saksida Bojan30-Nov-09 7:45

30-Nov-09 7:45

Isn't that other way around? I think that Int32.TryParse uses Convert class and handles exception within

PIEBALDconsult30-Nov-09 8:00

30-Nov-09 8:00

No, and I mispoke somewhat, both Convert.Toint32 ( string ) and Int32.Parse ( string ) call System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)

System.FormatException: Input string was not in a correct format.
   at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at System.Convert.ToInt32(String value)
   at Template.Template.Main(String[] args)
System.FormatException: Input string was not in a correct format.
   at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at System.Int32.Parse(String s)
   at Template.Template.Main(String[] args)

I would expect Int32.TryParse to also call ParseInt32.

Saksida Bojan30-Nov-09 8:06

30-Nov-09 8:06

Thanks for the info

Saksida Bojan30-Nov-09 8:14

30-Nov-09 8:14

It seems I Prefer using Convert.ToInt32 instead Int32.TryParse

With try parse I need to convert initial value to String, while convert accept other types

PIEBALDconsult30-Nov-09 8:17

30-Nov-09 8:17

Your original post specifically showed a string, what else are you trying to "convert"?

Saksida Bojan30-Nov-09 8:44

30-Nov-09 8:44

That was nearly an example. I meant overall usage

This time it was Decimal to Double

PIEBALDconsult30-Nov-09 9:12

30-Nov-09 9:12

Saksida Bojan wrote:
Decimal to Double

Why not just cast?

Saksida Bojan30-Nov-09 10:05

30-Nov-09 10:05

Haven't try to cast it

MCV Pattern in 2 threads for GUI and Worker ?

ThatsAlok30-Nov-09 22:49

ThatsAlok

30-Nov-09 22:49

Saksida Bojan wrote:
Haven't try to cast it

cast will remove decimal part if casting from double to int.

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User 260419330-Nov-09 6:33

User 2604193

30-Nov-09 6:33

Hi!

I am trying to set up a generic framework for applications following the Model Controller View pattern with a (main) GUI thread and a worker thread actually handling the data. I want this to reliable prevent the GUI from freezing and to enforce strict GUI/data/algorithm separation.

My idea is to have one single Worker thread in order to rid me off the problem of having to make all data accesses thread safe(?!), since there is just this one thread accessing the data.

So I would have the main thread containing the GUI and a Worker Thread for Model/Controller. The worker thread would start up when the application starts and close down when the application closes.
For the general setup I could think of a Producer/Consumer pattern with a worker thread that has a ThreadedQueue, that is the GUI thread can dispatch jobs to the Controller in the worker thread wich are then processed in the order they have been enqueued.
For simplicity the Controller can have a state machine (simplest busy/idle) that could actually prevent jobs being enqueued while it's too busy.

Now the practical problem I have is how to set up communication across the threads as needed in the MCV pattern? The main issue I see is that the View might request data from the model while the controller is actually changing this data.

Thus my idea was to have the View issue a job to the controller that requests the data and supplying a callback/delegate to be called from the Controller/Model. Since the callback is called from the Model/Controller thread it is positively thread safe if the callback is blocking and does not return before the data has actually been read by the View (using Invoke() within the GUI Form/Control functions).

Could this work, or did I oversee something obvious here ?
Does anyone know about some good ideas on this or a hint to some article where something similar is described?

modified 2-Aug-18 21:02pm.

Re: MCV Pattern in 2 threads for GUI and Worker ?

Luc Pattyn30-Nov-09 6:38

Luc Pattyn

30-Nov-09 6:38

Hi,

I'm still struggling with a good MVC approach myself, so I don't have the complete answer to your question, however this[^] might be useful to you.

Smile | :)

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I need help - problem with query builder in c#

TGiril30-Nov-09 6:26

TGiril

30-Nov-09 6:26

I have a small project in c# and ms-access. I use query builder to manage my tables in ms-access.

The problem is, select query works great, update query works great, but delete doesn't work and there is no error message!

Please help.
================================

using (cn)
{
OleDbDataAdapter adapter = new OleDbDataAdapter();
string queryString = "SELECT [A],[B] FROM [C]";
cn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + _conStrName + ";User Id=admin;Password=;";
OleDbConnection connection = new OleDbConnection(cn.ConnectionString);
adapter.SelectCommand = new OleDbCommand(queryString, connection);
OleDbCommandBuilder builder = new OleDbCommandBuilder(adapter);

adapter.SelectCommand.CommandText = queryString;
adapter.DeleteCommand = builder.GetDeleteCommand();
adapter.Update(ds.Tables["resourcesToTasks"]);

return ds;
}

Please help. Printing datagridview issue...

JollyMansArt30-Nov-09 5:11

JollyMansArt

30-Nov-09 5:11

I have learned a lot doing this project with datagrid views. But I have one issue though minor to me is a major issue to the client. I have been working on this for over 2 weeks and can not find any examples to give me the output I am looking for.

Please Help any Ideas please:

What I need to be able to do is essentially print my database grid column header names vertically at a 90.0F angle. Not horizontally as the default.
I have learned how to do this to the grid itself so it prints correctly on the screen. Which is:

private void dgvReport_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            
            if (e.RowIndex == -1 && e.ColumnIndex >= 4)
            {
                e.PaintBackground(e.ClipBounds, true);
                Rectangle rect = 
                    this.dgvReport.GetColumnDisplayRectangle(e.ColumnIndex, true);
                Size titleSize =
                    TextRenderer.MeasureText(e.Value.ToString(), e.CellStyle.Font);
                if (this.dgvReport.ColumnHeadersHeight < titleSize.Width)
                    this.dgvReport.ColumnHeadersHeight = titleSize.Width;

                e.Graphics.TranslateTransform(0, titleSize.Width);
                e.Graphics.RotateTransform(-90.0F);

                e.Graphics.DrawString(e.Value.ToString(), e.CellStyle.Font, //this.Font,
                    Brushes.Black, new PointF(rect.Y, rect.X));

                e.Graphics.RotateTransform(90.0F);
                e.Graphics.TranslateTransform(0, -titleSize.Width);
                e.Handled = true;
            } 
            
        }

But When I send the grid to the printer the columns are all horizontal not vertical. What can I do to print the columns vertical. Any examples anywhere?

Re: Please help. Printing datagridview issue...

JollyMansArt30-Nov-09 11:23

JollyMansArt

30-Nov-09 11:23

Found the solution

StringFormat CellFormat = new StringFormat();
            //CellFormat.Trimming = StringTrimming.Word;
            CellFormat.FormatFlags = StringFormatFlags.LineLimit | StringFormatFlags.NoClip | StringFormatFlags.NoWrap | StringFormatFlags.DirectionVertical;
            CellFormat.Alignment = StringAlignment.Center;

g.DrawString(column.HeaderText,
                        cell.Font(scale),
                        new SolidBrush(cell.ForeColor()),
                        CellBounds,
                        CellFormat);

The StringFormatFlags.DirectionVertical transforms the text vertically. Their is no need to picture draw the text vertically.

Regex question

kanchoette30-Nov-09 4:28

kanchoette

30-Nov-09 4:28

I hace some code which starts:

<br />
if (textBox1.Text.Length > 0)<br />
            {<br />
                String pat = "*.csv";<br />
                Regex r = new Regex (pat, RegexOptions.IgnoreCase);<br />
                Match m = r.Match(textBox1.Text);<br />
                if (m.Success)<br />
                {<br />
                    GetCSV(textBox1.Text);<br />
                }<br />

which is giving me the error: "parsing "*.csv" - Quantifier {x,y} following nothing."

What am I doing wrong please?

Re: Regex question

OriginalGriff30-Nov-09 4:47

OriginalGriff

30-Nov-09 4:47

Everything?

Regex pattern patching is not as simple as "*.xxx" for file name: '*' means "repeated zero or more times" and '.' means any character.

If you are trying to match the entire text box with a wild card filename, then why not just do:

if (textBox1.Text == "*.csv")
   {
   ...
   }

since that will work.

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Re: Regex question

PIEBALDconsult30-Nov-09 4:58