RowCount of a DataTable - C# Discussion Boards

S. Senthil Kumar10-Sep-05 4:40

10-Sep-05 4:40

If your socket object is a class level member variable, then yes, there's no need to pass it as in the state parameter.

Having it as a local variable gives a very minor advantage, the GC will be able to collect the socket object quicker, as there will be no outstanding references once the callback completes. Having it as a member variable means that the reference will be valid till the parent class is alive.

Not worth making it as a local variable just for that though.

Regards
Senthil
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Math troubles

KaptinKrunch9-Sep-05 15:02

KaptinKrunch

9-Sep-05 15:02

I'm looking for assistance with writing the following calculation in C#

n!
n_P_k = --------
(n - k)!

and/or

n!
n_C_k = ----------
k!(n - k)!

any ideas would be helpful!

-- modified at 21:03 Friday 9th September, 2005

Re: Math troubles

S. Senthil Kumar9-Sep-05 22:19

S. Senthil Kumar

9-Sep-05 22:19

You only need a function to calculate the factorial of a number. You can then pass it n and n-k and then divide to get n_P_K. A simple implementation of factorial will look like this

long factorial(int n)
{
  int x = 1;
  for (int i = 2; i<=n; ++i) x*= i;
  return x;
}

Regards
Senthil
_____________________________
My Blog | My Articles | WinMacro

Re: Math troubles

Member 19610719-Sep-05 23:04

Member 1961071

9-Sep-05 23:04

using System;

namespace fact
{
///

/// Summary description for Class1.
///

class Class1
{
///

/// The main entry point for the application.
///

[STAThread]
static void Main(string[] args)
{
//calculate n!
Console.WriteLine("Enter the value of N");
int nFact = 1;
int nComputeTo =int.Parse(Console.ReadLine());

int nCurDig = 1;
for (nCurDig=1;nCurDig <= nComputeTo; nCurDig++)
nFact *= nCurDig;
int Nfactorial=nFact;
Console.WriteLine("n! = "+nFact+"\n");

//calculate (n-k) !
Console.WriteLine("Enter the value of K");
int nFact1 = 1;
int k=int.Parse(Console.ReadLine());

int nComputeTo1=nComputeTo-k;//n-k

int nCurDig1 = 1;
for (nCurDig1=1;nCurDig1 <= nComputeTo1; nCurDig1++)
nFact1 *= nCurDig1;
int NminusKfactorial=nFact1;

try
{
int npk=Nfactorial/NminusKfactorial;//n_p_k=n!/(n-k)!
Console.WriteLine("(n-k)! = "+nFact1+"\n");
Console.WriteLine(" n_p_k="+npk);
Console.ReadLine();
}
catch(DivideByZeroException ex)
{
Console.WriteLine(ex.Message);
}
catch(OverflowException ex)
{
Console.WriteLine(ex.Message);
}
catch(Exception e)
{
Console.WriteLine(e.Message);
}

}
}
}

Re: Math troubles

Andy Brummer10-Sep-05 6:33

Andy Brummer

10-Sep-05 6:33

You can simplify your code for P(n, k):

int P(n, k)
{
   int value = 1;
   for(i = n; i>k; --i)
      value *= i;
   return value;
}

int C(n, k)
{
   return P(n, k)/P(k,1);
}

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

Re: Math troubles

KaptinKrunch10-Sep-05 8:39

KaptinKrunch

10-Sep-05 8:39

Thanks for all the suggestions. Now another question.
What data type should be used for numbers > long?

The above examples work great for 10_P_4 but I'm getting divide by zero's for 100_P_10.

I belive it's because 100! > long.

using this routine -----

long x = 1;
for(long i = 2; i <=n; ++i)
x *= i;

Debug info ----
n=100
i=2;x=2
i=3;x=6
i=4;x=24
i=5;x=120
i=6;x=720
i=7;x=5040
i=8;x=40320
i=9;x=362880
i=10;x=3628800
i=11;x=39916800
i=12;x=479001600
i=13;x=6227020800
i=14;x=87178291200
i=15;x=1307674368000
i=16;x=20922789888000
i=17;x=355687428096000
i=18;x=6402373705728000
i=19;x=121645100408832000
i=20;x=2432902008176640000
i=21;x=-4249290049419214848
i=22;x=-1250660718674968576
i=23;x=8128291617894825984
i=24;x=-7835185981329244160
i=25;x=7034535277573963776
i=26;x=-1569523520172457984
i=27;x=-5483646897237262336
i=28;x=-5968160532966932480
i=29;x=-7055958792655077376
i=30;x=-8764578968847253504
i=31;x=4999213071378415616
i=32;x=-6045878379276664832
i=33;x=3400198294675128320
i=34;x=4926277576697053184
i=35;x=6399018521010896896
i=36;x=9003737871877668864
i=37;x=1096907932701818880
i=38;x=4789013295250014208
i=39;x=2304077777655037952
i=40;x=-70609262346240000
i=41;x=-2894979756195840000
i=42;x=7538058755741581312
i=43;x=-7904866829883932672
i=44;x=2673996885588443136
i=45;x=-8797348664486920192
i=46;x=1150331055211806720
i=47;x=-1274672626173739008
i=48;x=-5844053835210817536
i=49;x=8789267254022766592
i=50;x=-3258495067890909184
i=51;x=-162551799050403840
i=52;x=-8452693550620999680
i=53;x=-5270900413883744256
i=54;x=-7927461244078915584
i=55;x=6711489344688881664
i=56;x=6908521828386340864
i=57;x=6404118670120845312
i=58;x=2504001392817995776
i=59;x=162129586585337856
i=60;x=-8718968878589280256
i=61;x=3098476543630901248
i=62;x=7638104968020361216
i=63;x=1585267068834414592
i=64;x=-9223372036854775808
i=65;x=-9223372036854775808
i=66;x=0
i=67;x=0
i=68;x=0
i=69;x=0
i=70;x=0
i=71;x=0
i=72;x=0
i=73;x=0
i=74;x=0
i=75;x=0
i=76;x=0
i=77;x=0
i=78;x=0
i=79;x=0
i=80;x=0
i=81;x=0
i=82;x=0
i=83;x=0
i=84;x=0
i=85;x=0
i=86;x=0
i=87;x=0
i=88;x=0
i=89;x=0
i=90;x=0
i=91;x=0
i=92;x=0
i=93;x=0
i=94;x=0
i=95;x=0
i=96;x=0
i=97;x=0
i=98;x=0
i=99;x=0
i=100;x=0

-- modified at 14:41 Saturday 10th September, 2005

Re: Math troubles

leppie10-Sep-05 10:04

leppie

10-Sep-05 10:04

use decimal or double then :p

^{xacc-ide 0.0.15 now with C#, MSIL, C, XML, ASP.NET, Nemerle, MyXaml and HLSL coloring - Screenshots}

RowCount of a DataTable

surfman199-Sep-05 14:14

surfman19

9-Sep-05 14:14

<br />
private void open_Database(string XML_DB_Name)<br />
{<br />
	dataSet.ReadXml(XML_DB_Name);<br />
	DataTable dt = dataSet.Tables[0];<br />
	string tblName = dt.TableName;<br />
	currentTable = dataSet.Tables[tblName];<br />
	dataGrid1.SetDataBinding(dataSet, tblName);<br />
	dataGrid1.CaptionText = tblName;<br />
<br />
	DataRow MyRow = currentTable.Rows[0];          <---- Problem when currentTable is empty, i get an exception...probably i can get the RowCount in another way?<br />
	int RowCount = MyRow.Table.Rows.Count;<br />
<br />
	// By default there is no DataGridTableStyle object.<br />
	// Add all DataSet table's style to the DataGrid<br />
	foreach(DataTable dTable in dataSet.Tables)<br />
	{<br />
		DataGridTableStyle dgStyle = new DataGridTableStyle();<br />
		dgStyle.MappingName = dTable.TableName;<br />
		if(RowCount < 8)<br />
		{<br />
			dgStyle.PreferredColumnWidth = 120;<br />
		}<br />
		else<br />
		{<br />
			dgStyle.PreferredColumnWidth = 110;<br />
		}<br />
		dataGrid1.TableStyles.Add(dgStyle);<br />
	}<br />
}<br />

i get this exception:
An unhandled exception of type 'System.IndexOutOfRangeException' occurred in system.data.dll
Additional information: There is no row at position 0.
But i want to have the rowcount also when its 0!!

cu

Re: RowCount of a DataTable

Expert Coming9-Sep-05 14:18

Expert Coming

9-Sep-05 14:18

surfman19 wrote:
DataTable dt = dataSet.Tables[0];

surfman19 wrote:
DataRow MyRow = currentTable.Rows[0]; <---- Problem when currentTable is empty, i get an

An array has to have at least 1 variable placeholder. Make the [0] to [1].

Re: RowCount of a DataTable

Andy Brummer9-Sep-05 14:49

Andy Brummer

9-Sep-05 14:49

In most C style languages like C#, array indexes usually start with 0 rather then 1. For loops usually follow this form.

for(int i=0; i<list.count; ++i)
="" do="" something="" with="" list[i]="" here=""

<hr="">

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

Re: RowCount of a DataTable

Gary Thom9-Sep-05 14:19

Gary Thom

9-Sep-05 14:19

if (currentTable.Rows.Count > 0)
{
}

Should help

Gary

Marc Clifton: "In other words, VB is like a bad parent. It can really screw up your childhood."

Re: RowCount of a DataTable

surfman199-Sep-05 14:20

surfman19

9-Sep-05 14:20

solved:

<br />
int RowCount = dt.Rows.Count;<br />

Deserialize Error

dicas9-Sep-05 13:50

dicas

9-Sep-05 13:50

I have a file that has a serialized object in it.
I wrote ANOTHER program that I wanted to read that object.
When I attempt to Deserialize I get the following execption:

Unable to find assemble 'Address, Version 1.0.0.0, Culture=neutral, PublicKeyToken=null

To make sure the second program new about the class object that was stored in the file, I copied the class to the new program. I also copied the Serialize and Deserialize code that works on the first program to the second program. The first program can read and write with no problems to this file. Both programs were created in MS's Visual C# 2005 Express Edition Beta.

Anybody have an idea why one program can not read a serialized file created by another program?

Thanks for any help,
Dave

Re: Deserialize Error

Guffa9-Sep-05 13:56

Guffa

9-Sep-05 13:56

You can't copy a class by coping the source code for it. That will only create a class that looks exactly the same, but it is not the same class.

Compile the class by itself, so that you can reference the dll from both programs.

---
b { font-weight: normal; }

Re: Deserialize Error

Daniel132410-Sep-05 2:21

Daniel1324

10-Sep-05 2:21

That still wont work. According to MSDN, a serialized stream will NOT deserialize in any program except the one that serialized it. Maybe of your new program has the same assembly name and such it may work.

I searched for days for this answer until I came scross that on MSDN.

How to make DebugView see my program

Susan Hernandez9-Sep-05 12:37

Susan Hernandez

9-Sep-05 12:37

Does anyone know how to make DebugView from SysInternals "work"? I am trying to write a C# program in .NET 2003 and to print 2 lines:

System.Diagnostics.Debug.WriteLine("I am debugging");
System.Diagnostics.Trace.WriteLine("I am Tracing");

I start dbgview.exe, run my program, and I do not see those comments (I checked that I am in debug mode). I have seen references to some kind of TraceListener, but I don't know what that is or where to set it up.

If anyone knows what I'm talking about, could you please link me to some pertinent info? My quick search on google didn't give me anything.

Thanks
Sue

Re: How to make DebugView see my program

Andy Brummer9-Sep-05 15:01

Andy Brummer

9-Sep-05 15:01

You can add a trace listener using your app.config file look here:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/gngrflistenerselement.asp[^]

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

Re: How to make DebugView see my program

Susan Hernandez12-Sep-05 6:00

Susan Hernandez

12-Sep-05 6:00

Thanks very much for the link. I can't seem to get it working yet, but I will keep looking around here.

I put in a TextWriterTraceListener, and that does nothing;
I put in an EventLogTraceListener, and that properly writes to the Event Log;
I put in a DefaultTraceListener, and that throws an error.

Thanks for the help.
Sue

Re: How to make DebugView see my program

S. Senthil Kumar9-Sep-05 22:27

S. Senthil Kumar

9-Sep-05 22:27

That's surprising. AFAIK, TraceListeners are useful if you want to monitor trace output within your application, they notify you when someone does a Trace.WriteLine or something similar.

You should be seeing the messages in DebugView without doing anything special. Are you able to see the messages in VS .NET's Output window?

Regards
Senthil
_____________________________
My Blog | My Articles | WinMacro

Re: How to make DebugView see my program

Susan Hernandez12-Sep-05 6:06

Susan Hernandez

12-Sep-05 6:06

I did not realize I could see the output there Blush | :O

. I fired it up, and yes, I can see the output in the output window.

I still cannot see it in DebugView though! I tried the suggestion from the other poster to add a trace listener app.config section but that didn't seem to work.

I can get a lot of information, though, just by using the output window. Man, I feel like an amateur!

Data Table Error

Expert Coming9-Sep-05 11:48

Expert Coming

9-Sep-05 11:48

//Create the variables and arrays need only for Creating the table<br />
string[] skills = new string[1];<br />
skills[0] = "attack";<br />
//skills[1] = "strength";<br />
//skills[2] = "defence";<br />
<br />
//The creation of the table that shows the user their stats from the database<br />
//Dynamic Creation of the datatable<br />
<br />
///Also sets up the new datatable<br />
DataTable dtshowskills = new DataTable("USkills");<br />
<br />
DataColumn userSkill = new DataColumn("Skill");<br />
dtshowskills.Columns.Add("userSkill");<br />
DataColumn userLevel = new DataColumn("Level");<br />
dtshowskills.Columns.Add("userLevel");<br />
<br />
foreach (string skill in skills)<br />
{<br />
DataRow drskill = dtshowskills.NewRow();<br />
drskill["userSkill"] = skill;<br />
drskill["userLevel"] = 0;<br />
dtshowskills.Rows.Add(drskill);<br />
}<br />
<br />
dgSkills.DataSource = dtshowskills;<br />
dgSkills.DataBind();

//This is on my actual web page<br />
<asp:DataGrid ID="dgSkills" Runat="server" />

I don't understand DataTables, and I am going to do some reading up on them, but for now, someone please help me. I had help on most of it a while ago, any help is appricated.

Re: Data Table Error

Andy Brummer9-Sep-05 12:26

Andy Brummer

9-Sep-05 12:26

I'm not sure what error you are getting since you didn't list it, but I'm guessing it is because you havne't set the data types of the DataColumns. Post the problem and we can help you out.

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

Re: Data Table Error

Expert Coming9-Sep-05 12:41

Expert Coming

9-Sep-05 12:41

Oops, sorry I thought that I did post the error. My bad. Here is the error:

System.NullReferenceException: Object reference not set to an instance of an object.

Re: Data Table Error

Alomgir Miah9-Sep-05 13:37

Alomgir Miah

9-Sep-05 13:37

DataColumn userSkill = new DataColumn("Skill");
dtshowskills.Columns.Add("userSkill");
DataColumn userLevel = new DataColumn("Level");
dtshowskills.Columns.Add("userLevel");

foreach (string skill in skills)
{
DataRow drskill = dtshowskills.NewRow();
drskill["userSkill"] = skill;
drskill["userLevel"] = 0;
dtshowskills.Rows.Add(drskill);
}

should instead read

DataColumn userSkill = new DataColumn("Skill");
dtshowskills.Columns.Add(userSkill);
DataColumn userLevel = new DataColumn("Level");
dtshowskills.Columns.Add(userLevel);

foreach (string skill in skills)
{
DataRow drskill = dtshowskills.NewRow();
drskill["Skill"] = skill;
drskill["Level"] = 0;
dtshowskills.Rows.Add(drskill);
}

Live Life King Size
Alomgir Miah

Re: Data Table Error

Guffa9-Sep-05 13:38

Guffa

9-Sep-05 13:38

You are creating DataColumn objects, but you don't use them. Instead you create columns that have the same name as the variables. To use the DataColumn objects that you create, do like this:

DataColumn userSkill = new DataColumn("Skill");<br />
dtshowskills.Columns.Add(userSkill);<br />
DataColumn userLevel = new DataColumn("Level");<br />
dtshowskills.Columns.Add(userLevel);

The columns will now be named "Skill" and "Level".

---
b { font-weight: normal; }

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