C# Discussion Boards - CodeProject

Re: sharing an event handler, not getting what I expect

1-Oct-07 5:49

Hi,

if you assign the same array/ArrayList/List as the DataSource of several ComboBoxes,
how would they exchange current selection info Confused | :confused:

They don't!

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

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TJoe1-Oct-07 5:56

Re: sharing an event handler, not getting what I expect

1-Oct-07 5:56

I think the BindingContext[^] on the form maintains it for each DataSource. Since each ComboBox has the same data source (e.g. ReferenceEquals would return true), then they all share the same "current record" (which is maintained by the BindingContext. Apparently, you can "group" data bound controls using Panels (or GroupBox, etc) but you have to set the BindingContext property on the Panel to override the Form's BindingContext.

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

JoeRip1-Oct-07 5:57

JoeRip

1-Oct-07 5:57

Well, Luc, try it out Smile | :)

.

The whole point of binding DataSources is to share the Binding Context, so that all of the controls point at the same "record" in the DataSource. That way you can have several controls on the form (like, say, Back/Forward/Edit/Delete, etc) that all deal with the same "row" or data in the source.

I had completely forgotten about this when I used "combo.DataSource = myArray". I was just looking for a cheap way to make all of the items in my array show up in the combo box.

TJoe is right, if I want each combo to have its own context to the data in my array, I need to either Clone each array and bind to it, or just copy the items from the array to the combo.Items collection manually.

Since there is no real advantage to making the array a DataSource here (I'm not really using the BindingContext for what its intended), I'm just doing the latter now.

Re: sharing an event handler, not getting what I expect [modified]

Luc Pattyn1-Oct-07 6:03

Re: sharing an event handler, not getting what I expect

1-Oct-07 6:03

JoeRip wrote:
try it out

OK, I'll add it on the todo list (not at the top though).

[added] checked. You're right, ComboBoxes sharing a DataSource, even a simple array,
become fully synchronized. I didn't know that. Thanks.[/added]

Smile | :)

-- modified at 12:24 Monday 1st October, 2007

Luc Pattyn [Forum Guidelines] [My Articles]

TJoe1-Oct-07 4:50

1-Oct-07 4:50

The collection object themselves do not maintain the current record. I believe the ComboBox and other controls maintain it. Specifically, the BindingContext[^]. It looks like if you add the ComboBoxes to a Panel, then that would create a new BindingContext.

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

Problem with macros

yadlaprasad1-Oct-07 3:29

yadlaprasad

1-Oct-07 3:29

Hi all,

I am working with Visual studio Macros.
I created one macro.and i assigned one keyboard shortcut to run that macro in VS 2005 Applications.its wrkng fine.

But my problem is when i taken new application when i wrk wth this shortcut macro is not firing.

So,to make macros global to all applications what to do?

krishna Prasad

fttyhtrhyfytrytrysetyetytesystryrty

Re: Problem with macros

TJoe1-Oct-07 3:48

help with code to implement a calculator....

1-Oct-07 3:48

I believe you need to restart VS after assigning the shortcut. Basically, VS saves changes when it exits. So if you open VS, assign the shortcut, then open another instance of VS then the second instance will not have the assigned shortcut. This is typical of most settings in VS.

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

MinhajuddinK1-Oct-07 3:25

MinhajuddinK

1-Oct-07 3:25

Hi all,

I am new to C#....

I thought that implementing a simple calculator would help me understand the language... I have come up with a code....

It would be great if the gurus here give me feedback on this...

<br />
using System;<br />
using System.Collections.Generic;<br />
using System.Text;<br />
<br />
namespace Calculator<br />
{<br />
    class compute<br />
    {<br />
        private string[] inputNumbers;<br />
        public string computeResult(string inputExpression)<br />
        {<br />
            string result = "There was an error while processing!";<br />
            inputExpression = inputExpression.Replace("+", "+A");<br />
            inputExpression = inputExpression.Replace("-", "-S");<br />
            inputExpression = inputExpression.Replace("*", "-M");<br />
            inputExpression = inputExpression.Replace("/", "/D");<br />
<br />
            if (inputExpression.Substring(0, 1) != "-" && inputExpression.Substring(0, 1) != "+")<br />
                inputExpression = "A" + inputExpression;<br />
            else<br />
                inputExpression = inputExpression.Substring(1);<br />
            inputNumbers = inputExpression.Split('+', '-', '*', '/');<br />
<br />
            decimal output=0;<br />
            int i;<br />
            int count = inputNumbers.Length;<br />
            for (i = 0; i < count; i++)<br />
            {<br />
                string calc = "";<br />
                inputNumbers[i] = inputNumbers[i].Trim();<br />
                decimal temp;<br />
                if (!decimal.TryParse(inputNumbers[i].Substring(1),out temp))<br />
                    break;<br />
                calc = inputNumbers[i].Substring(0,1);<br />
<br />
                switch(calc)<br />
                {<br />
                    case "A":<br />
                        output = output + temp;<br />
                        break;<br />
                    case "S":<br />
                        output = output - temp;<br />
                        break;<br />
                    case "M":<br />
                        output = output * temp;<br />
                        break;<br />
                    case "D":<br />
                        output = output / temp;<br />
                        break;<br />
                }<br />
<br />
                <br />
            }<br />
            <br />
            if(i==count)<br />
                result = output.ToString();<br />
            return result;<br />
        }<br />
    }<br />
}<br />
<br />

You don't have to be ~~AFRAID!~~

Re: help with code to implement a calculator....

led mike1-Oct-07 4:43

led mike

1-Oct-07 4:43

Minhaj.Net wrote:
I have come up with a code....

It would be great if the gurus here give me feedback on this...

Yes that does appear to be code

Did you read the first message in the forum titled, "How to get an answer to your question"?

Re: help with code to implement a calculator....

Luc Pattyn1-Oct-07 4:55

Re: help with code to implement a calculator....

1-Oct-07 4:55

Hi,

I think this will work most of the time; I have several comments though:

1.
please post multi-line code in PRE tags instead of CODE tags; that would preserve
indentation.

2.
your error handling is insufficient; at the bare minimum you should put all code inside
a try-catch construct.

3.
your handling of operators is quite creative; replacing them to keep a trace when
they tend to disappear by the Split()...
the line Replace("*", "-M"); is probably not what you intended, but it does
nof affect the outcome.
You don't really need the letters ASMD, you could have duplkcated the operators instead.

4.
there are some functional shortcomings:
- you only handle diadic operators (that's having two operands); what if you need
a monadic minus, as in "-4 * -3" ?
- you fail to obey the operator priorities: "2+3*4" should give 14, not 20.
the right way to fix this is by using a stack machine, i.e. postpone the operator (+)
and push the operands, until another operator of same or lower priority is seen (or end
of expression), then pop operands, perform operation and push result.

5.
programming details:
- you could replace for (i = 0; i < count; i++) by foreach(string inputNumber in inputNumbers)
- to get some character from a string, you don't need Substring(x,1); you can index as
in inputNumbers[i][0] which gives the leading char (unless length is 0)

Keep up the good work! May I suggest you read several CodeProject articles...

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

MinhajuddinK1-Oct-07 7:32

MinhajuddinK

1-Oct-07 7:32

Thank you very much Luc Pattyn!

that will really help me....
I would like to go through the articles here.... But with so many of them, I find it a bit difficult to chose....

Thanks for the advice Smile | :)

You don't have to be ~~AFRAID!~~

Ambiguous Date Format in Excel

meeram3951-Oct-07 3:21

meeram395

1-Oct-07 3:21

Hi,

In my C# application, I'm getting a dataset from the database for transport to excel. In the data set there is a date column. While writing to excel it is giving an entire different format, whereas in dataset it is coming correctly. For eg:
if in the dataset suppose the date is 03/12/2006, while writing to excel it is writing as 2006-12-03T00:00:00.0000000+05:30. I don't know how this is happening. I'm using RKLib dll for exporting the data to excel. Anybody who knows will you please help? This is urgent.

Thanks,

Meeram395

Re: Ambiguous Date Format in Excel

raja mohamed21-Jul-09 2:15

raja mohamed

21-Jul-09 2:15

hi friend use this format

Rose | [Rose]

CONVERT(VARCHAR(15),AC.CGO_RVD_DAT ,103)

System.IO.Compression

Vodstok1-Oct-07 3:12

1-Oct-07 3:12

I have been searching google for an answer for this, and maybe i just dont know how to proeprly word my search, but I have come back with nothing useful. My issue:

I have been playing around with the System.IO.Compression namespace, and have noticed an interesting little behavior:
Compressing files that are already in a compressed format (example: jpg, mpg, zip) or have been encrypted with System.Security.Cryptography, come out of the compression BIGGER than when they went in.

I was wondering if anyone A. knows why this happens, and B. knows a way around it

If there is no way around it, then my code has to be modified to exclude formats that might have this issue, but it would be swell to be able to just compress the buggers.

______________________
Mr Griffin, eleventy billion is not a number... WTF | :WTF:

TJoe1-Oct-07 3:16

1-Oct-07 3:16

Since you are compressing something that is already compressed, then you won't be able to make it smaller. But while compressing the second time, the code still needs to add a header to decompress it. So if the original data has X bytes, then the compressed version would (approximately) have X + Y, where Y is the header.

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

Vodstok1-Oct-07 3:22

1-Oct-07 3:22

Great! I know it seems weird that I would be excited, but as long as I understand what is going on under the hood, I can work around it.

That is a huge help. So I have to specify which files will be compressed and which wont, Oh Well.

if i didnt like to code, i wouldnt do this for a living Smile | :)

______________________
Mr Griffin, eleventy billion is not a number... WTF | :WTF:

TJoe1-Oct-07 3:25

1-Oct-07 3:25

Assuming the compression is not expensive (e.g. you are only working with small streams), then you could simply code the method such that it tries to compress the data. Then it would compare the original size to the compressed size and if the compressed size is larger, then it saves the original data and trashes the compressed data. You would probably need to maintain a flag with the file that specifies whether you compressed it though.

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

Vodstok1-Oct-07 3:33

1-Oct-07 3:33

I have a pretty good idea of which filetypes are compressed or not, so i will probably integrate what you suggested with an enum or something that will look at the extension. The code i am writing will possible handle hundreds of files at a time, and any memory overhead i can save will be good.

Thanks again for your help, you have saved me a headache.

______________________
Mr Griffin, eleventy billion is not a number... WTF | :WTF:

Scott Dorman1-Oct-07 3:25

Scott Dorman

1-Oct-07 3:25

This is fairly typical. Once a file has been compressed, compressing it again very rarely makes it smaller still. As Tom pointed out, the second compression adds additional header information to the file, which ends up making it bigger. There really isn't a way around this.

Scott.

—In just two days, tomorrow will be yesterday.

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Luc Pattyn1-Oct-07 5:03

1-Oct-07 5:03

Hi,

the best way to compress a collection of files is to turn them over all at once to one of the
popular compression utilities such as WinZip. You will then again notice that some files
don't get extra compression (such as ZIP files!), but the overhead will be minimal and mostly
shared.

The command line interface to WinZip requires a separate install, once installed you can
call it using Process.Start().

There also are Zip libraries available (such as ZLIB), search the CodeProject articles.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Vodstok1-Oct-07 5:08

1-Oct-07 5:08

Great suggestion, however, the issue i have is that each file is to be saved to a database, and each file has to be its own seperate entity. The other thing is that i cant have the user installing a seperate utility, it needs to be all in one package.

I already have an interface in the works for saving the files, so modifying the code for "non-compressable" formats should be a cinch.

______________________
Mr Griffin, eleventy billion is not a number... WTF | :WTF:

Luc Pattyn1-Oct-07 5:59

1-Oct-07 5:59

OK.

One way for predicting compressability is by performing a simple statistical analysis:
take part of the file (say the first 1KB) and make a histogram on the byte values.
If the histogram is very flat, chances are compression wont buy you anything;
if a lot of byte values occur very (in)frequently, compression should work well.

One measure could be:

int infrequent=number of values occuring less than samplesize/512;
int frequent=number of values occuring more than samplesize/128;
bool compression_will_work=infrequent+frequent>64; // experiment with the constant here!

Luc Pattyn [Forum Guidelines] [My Articles]

Vodstok1-Oct-07 6:21