Re: Null reference problem - C# Discussion Boards

DataGrid & Large Integers

16-Aug-03 16:52

yes, one need to scarfice a lot to earn the know-how. sweet and sour

norm

Member 7681714-Aug-03 4:11

Re: DataGrid & Large Integers

14-Aug-03 4:11

Hey everyone,

Here's the prob: I am importing a set of data from a CSV file using the Microsoft Text Reader into a dataset, and later into a datagrid for previewing the data, the problem is that there is a column that contains very large numbers, 16 digits long. When I view the data in the datagrid, or when I export it back into CSV, the numbers get mangled into, say 6.00034+E. Since I don't perform any mathematical calculations on these numbers, I could just change the data type to text in the dataset but apparently that is not possible? So I found the BoundColumn.DataFormatString in the System.Web.UI.WebControls namespace but my program is a windows app. Any pointers would be extremely appreciated.

Thanks!

-Abraham

Ista14-Aug-03 6:47

Ista

14-Aug-03 6:47

why not do the transformation in the stored procedures. That would be simple

SELECT MyNumber = STR(Column1)

I'm not an expert yet, but I play one at work. Yeah and here too.

Re: DataGrid & Large Integers

Member 7681714-Aug-03 7:59

Re: DataGrid & Large Integers

14-Aug-03 7:59

Thanks for your reply, Ista.

I tried that, but let's say I bring in the number 6000645657564980, and it gets garbled as 600064+E in the datagrid if I then convert it back to string,
whether in SQL or C#, it gives me back 6000640000000000. Any suggestions?

Ista14-Aug-03 8:36

Ista

14-Aug-03 8:36

specify the column as a DataGridTextBoxColumn()

I'm not an expert yet, but I play one at work. Yeah and here too.

Null reference problem

vaslui14-Aug-03 3:56

vaslui

14-Aug-03 3:56

Did you have the same problem as I do now ? I call a member function of an object that must return an object, the member function works well it creates the object to be returned and even it returns the object but the caller does not receive anything. The strange part is that at debug time the caller actually receive the object, but when build and run the project everinthing goes wrong and I have the upper problem Cry | :((

pls help me

I'll show you some piece of code and I can show you more if necessary:

private void btnOk_Click(object sender, System.EventArgs e)<br />
{<br />
   if(txtUserName.Text.Equals(String.Empty))<br />
   {<br />
     MessageBox.Show("pls insert the username !!!");<br />
     return;<br />
   }<br />
   if(txtPassword.Text.Equals(String.Empty))<br />
   {<br />
     MessageBox.Show("pls insert a password !!!");<br />
     return;<br />
   }<br />
<br />
   if (componenta != null)<br />
   {<br />
     medic = componenta.MedicLogin(txtUserName.Text,txtPassword.Text);<br />
     if(medic != null)<br />
     {<br />
       lblData.Text = medic.FirstName;		<br />
     }<br />
     else<br />
     {<br />
       MessageBox.Show("medic null");<br />
       return;<br />
     }<br />
   }<br />
   else<br />
   {<br />
     MessageBox.Show("componeta nula");<br />
   }<br />
}

I must say also that in a console application the previous problem does not apear.

Re: Null reference problem

Frank Olorin Rizzi14-Aug-03 6:15

Frank Olorin Rizzi

14-Aug-03 6:15

I'm not sure if this is the routine that calls (and receives -in some cases- the null reference back) or if it is the one that is called (and sends back the null reference in some cases).

In either case, which line is the one where you find the null reference?

Since you mention that this problem doesn't appear in a console application...
...what is different in the trouble case vs the non-trouble one?
[I see a btnOK_Click name there, which seems to hint that this is part of a Win App project, with GUI and buttons and all that... maybe the case of a console application is much more simple, and the difference might be in some included library...]

F.O.R.

write XML CDATA

devvvy13-Aug-03 22:34

adding color to a form's title

13-Aug-03 22:34

Guys, can you do something like this?

CCustomObj obj = new CCustomObj();

XmlTextWriter wr = new XmlTextWriter("outputXml.xml", null);
wr.Formatting = Formatting.Indented;

wr.WriteStartDocument();

wr.WriteStartElement("GraphicCollection");
wr.WriteAttributeString("objID", "12345");
wr.WriteCData(obj); //Can you write the binary memory map/layout of the object with C#? And restore it later on? I know WriteCData(String) does not accept "byte". Any alternative?

wr.WriteEndElement();
wr.WriteEndDocument();

wr.Flush();

wr.Close();

Thanks

norm

Member 50926213-Aug-03 22:03

Member 509262

13-Aug-03 22:03

if i have a form and it has a title of 'Test Application' and i want to change it to 'Test Application - UNREGISTERED' and have the UNREGISTERED in red, is this possible?

thanks,
Rob Tomson

--
There are 10 kinds of people. Those who understand binary and those who don't.

interesting find but why?

Member 50926213-Aug-03 21:01

Member 509262

13-Aug-03 21:01

i have a background image on my form and i wanted to put a transparent label on it. however, i noticed that a label cannot have it's backcolor changed to 'transparent'. so i created a groupbox and placed a label in it. i then changed to backcolor of the groupbox to 'transparent' and the label's backcolor is now transparent! what the heck? is this a 'feature' of the groupbox or is there some other way of making a label transparent that i don't know about?

Rob

--
There are 10 kinds of people. Those who understand binary and those who don't.

Re: interesting find but why?

Member 50926213-Aug-03 21:21

Member 509262

13-Aug-03 21:21

*UPDATE*

i believe i've come across a bug. try these steps:
create a groupbox on a form and set the backcolor to 'transparent'.....works great

now change the backcolor back to 'control', change the flatstyle to 'system', then try to set the backcolor to 'transparent'.....error 'Invalid property value.' okay, so it won't let you have a transparent background while the flatstyle is set to system.

so change the flatstyle back to 'normal' and change the backcolor to 'transparent'. then change the flatstyle to 'system'.....works!? but it's really buggy, the display in the groupbox fails to update and when the program is run the background of the groupbox is weirded out.

i'm NOT using csharp 2003 so i don't know if they've fixed this in the new version or not. did they? why can the backcolor not be transparent if the flatstyle is set to 'system'?

Rob Tomson

--
There are 10 kinds of people. Those who understand binary and those who don't.

Re: interesting find but why?

James T. Johnson14-Aug-03 7:48

James T. Johnson

14-Aug-03 7:48

Rob Tomson wrote:
why can the backcolor not be transparent if the flatstyle is set to 'system'?

When you set the FlatStyle property to System you are telling the Framework to always let the OS do the drawing for that control. To my knowledge either none or not all of the .NET enabled OSes support the Transparent style which would require the Framework to emulate your choice but that goes against telling the framework to let the OS draw the control.

James

"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

Re: interesting find but why?

Ista16-Aug-03 16:27

Ista

16-Aug-03 16:27

even if you do a SetStyle method in the constructor. It works for most controls so since a label is a derivative of the control class you would thinks so.

SetStyle must be done in the constructor only by the way

I'm not an expert yet, but I play one at work. Yeah and here too.

Event syntax

devvvy13-Aug-03 20:10

13-Aug-03 20:10

Hi, having a little problem with Event syntax:

class SomeClass
{
public delegate int MyEventDelegate(int param);
public event MyEventDelegate MyEvent;

public int MyHandler(int param) {...};

public SomeClass()
{
MyEventDelegate d = new MyEventDelegate(this.MyHandler);
MyEvent += d; //Question: type (left side)= event, type (right side)=delegate (which is an "object" after code injected. But, it seems to me the type does match.
}

... the rest ...

};

Thanks!

norm

Member 7681714-Aug-03 4:16

14-Aug-03 4:16

Hi Norm,

Try this:

class SomeClass
{
public delegate int MyEventDelegate(int param);
public event MyEventDelegate MyEvent;

public int MyHandler(int param)
{
MessageBox.Show("A number has been added!");
}

public SomeClass()
{

MyEvent += new MyEventDelegate(MyHandler);
SomeAddFunction(1, 2);

}

// To Call the Event
private void SomeAddFunction(int a, int b)
{
int c = a + b;
MyEvent(c); // This will fire the event
}

This is my first attempt at showing something on a message board, I hope it helps!

-Abraham

devvvy14-Aug-03 4:59

14-Aug-03 4:59

Thanks for feedback. However, I think perhaps there's a bit of misunderstanding here. I understand how to hook up event handlers with event and fire it and all that. I understand how the compiler injects code into the source and our "delegate" become a "class". What I do not understand is, however, the syntax:

int = int + int (the type matches, no problem)

But:

MyDelegate d = new MyDelegate(this.MyHandler);
this.MyEvent += d;

It seems to me type doesn't match up, here's why:

On LEFT SIDE of "+=", type is MyEvent --> It's an "event".
On RIGHT SIDE of "+=", type is MyDelegate --> It's a "delegate" (Of course it expands to a class).

How does it work? Or perhaps I'm asking too much. Sometimes, developers should just take it and code it. Thanks.

norm

Member 7681714-Aug-03 5:29

14-Aug-03 5:29

I really hope someone with more experience than me can follow up on this:
I think what goes on in the back is that there is an overloaded operator that adds the delegate (or function pointer) to a collection or list (the event model?), what goes on is not really saying MyEvent(event) EQUALS MyDelegate(delegate type), but saying "add this delegate to my list of function pointers to call when I'm triggered".

Or maybe your last sentence really summed it up!

Nick Parker14-Aug-03 7:47

Nick Parker

14-Aug-03 7:47

norm wrote:
MyDelegate d = new MyDelegate(this.MyHandler);
this.MyEvent += d;

The event hold a *linked-list* of delegates, d becomes an instance of that delegate and is added to the chain. This way, we check to make sure there are items in the *linked-list* and then fire the event:

void OnMyEvent(string str)
{
   if(MyEvent != null) // check to see if a delegate is registered
      MyEvent(str);
}

HTH

-Nick Parker

Member 7681714-Aug-03 8:00

14-Aug-03 8:00

Woa! I wasn't that far off.. I shall celebrate with a cold one after work!

devvvy15-Aug-03 20:05