Re: Exception....PLSSSS HELPPPP - C# Discussion Boards

Re: Exception....PLSSSS HELPPPP :((

2-Oct-09 23:13

im not workin.......im a student....searchin for doubts!!

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Christian Graus2-Oct-09 23:14

Re: Exception....PLSSSS HELPPPP :((

2-Oct-09 23:14

If you want to be a student, start by buying books, not by guessing what code you think will work. Then you will be fine. Buy a book.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

nagendrathecoder2-Oct-09 23:15

2-Oct-09 23:15

Then its really advisable for you to read a book first. Smile | :)

I still didn't understand the logic of posting same question. D'Oh! | :doh:

linto_112-Oct-09 23:22

2-Oct-09 23:22

Tks a lot for ur advice....i'll look that i buy a book nd study first..tks!!

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linto_112-Oct-09 23:25

2-Oct-09 23:25

Can u help me with which books to study????.....i wld b very much thankful!!

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nagendrathecoder2-Oct-09 23:28

2-Oct-09 23:28

Buy any book for Beginners in C#.Net.

Richard MacCutchan2-Oct-09 23:29

Richard MacCutchan

2-Oct-09 23:29

linto_11 wrote:
Can u help me with which books to study

Well, since you posted this question in the C# forum, I think the first one you need is on C#. If you want to start immediately then .NET Book Zero[^] will get you going.

Christian Graus2-Oct-09 23:57

2-Oct-09 23:57

At this point, I can't imagine there is a book that WOULDN'T help. Just learning to use google and read the MSDN would be a huge help. Just buy a cheap book on C#, that is for beginners. The 24 hour or the dummies books are a good place to start.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Richard MacCutchan2-Oct-09 23:27

Richard MacCutchan

2-Oct-09 23:27

Don't forget one on how to write clearly, without using txtspk!

Christian Graus2-Oct-09 23:43

2-Oct-09 23:43

I love it when I'm the one who gives the answer, and they won't respond to anything I say.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Exception in C#

linto_112-Oct-09 22:11

2-Oct-09 22:11

HI,
Im gettin an exception saying "InvalidOperationException" nd it says "No data exists for the row/coloumn", for the following code, nd d exception results on the d line that has been underlined....please check d code nd help....plssss!!!!

int rnd;
int totalcount = 0;
Random SelectRandom = new Random();
OleDbConnection access = new OleDbConnection();
OleDbCommand accesscmd = new OleDbCommand();
OleDbDataReader reader;
if (combo_Category.Text == "Book")
{
string connectionstring = "Provider = Microsoft.Jet.OLEDB.4.0;
Data Source = |DataDirectory|\\HangmanDatabase.mdb";
access.ConnectionString = connectionstring;
access.Open();
accesscmd.CommandText = "Select * From Book";
accesscmd.Connection = access;
reader = accesscmd.ExecuteReader();
while (reader.Read())
{
totalcount = totalcount + 1;
}
if (reader.HasRows)
{
rnd = SelectRandom.Next(0,totalcount - 1);
book = reader[0].ToString();
datastring = book.ToCharArray();
}
access.Close();
convert();
}

Pleassssssss help!!!

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nagendrathecoder2-Oct-09 22:30

2-Oct-09 22:30

You have to put following code:

linto_11 wrote:
if (reader.HasRows)
{
rnd = SelectRandom.Next(0,totalcount - 1);
book = reader[0].ToString();
datastring = book.ToCharArray();
}

inside While(reader.Read()) loop.
If u put that code inside while then u don't need if(reader.HasRows) loop.
Also, call reader.Close() before access.Close().

Hope it'll solve ur problem.

linto_112-Oct-09 22:43

2-Oct-09 22:43

nagendrathecoder wrote:
inside While(reader.Read()) loop.
If u put that code inside while then u don't need if(reader.HasRows) loop.
Also, call reader.Close() before access.Close().

Again it is creating the same issue.....sumthing serious.........please help!!!

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Christian Graus2-Oct-09 22:54

2-Oct-09 22:54

Do you know anything about programming at all ? How did you write this code, if you don't understand what it does ? If you get an exception saying you're trying to read something that's empty, then you need to check first to make sure it has data. That's what the message is telling you. You've changed your code, but not posted the code, or the exact error message. Have you tried to debug this code at all ? It doesn't seem to me like you're trying too hard to get help, or that you're doing anything to try to fix this beyond posting here and hoping we'll fill the gaps of your shortcomings.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

nagendrathecoder2-Oct-09 22:55

2-Oct-09 22:55

Try to do it like this:

int rnd;
int totalcount = 0;
Random SelectRandom = new Random();
OleDbConnection access = new OleDbConnection();
OleDbCommand accesscmd = new OleDbCommand();
OleDbDataReader reader;
if (combo_Category.Text == "Book")
{
string connectionstring = "Provider = Microsoft.Jet.OLEDB.4.0;
Data Source = |DataDirectory|\\HangmanDatabase.mdb";
access.ConnectionString = connectionstring;
access.Open();
accesscmd.CommandText = "Select * From Book";
accesscmd.Connection = access;
reader = accesscmd.ExecuteReader();
while (reader.Read())
{
totalcount = totalcount + 1;
rnd = SelectRandom.Next(0,totalcount - 1);
book = reader.GetValue(0).ToString();
datastring = book.ToCharArray();
}
reader.Close();
access.Close();
convert();
}

I have doubts on following line:
datastring = book.ToCharArray();
R u sure, this line work?

Also, what are you doing if reader is empty?

Christian Graus2-Oct-09 23:00

2-Oct-09 23:00

nagendrathecoder wrote:
totalcount = totalcount + 1;
rnd = SelectRandom.Next(0,totalcount - 1);
book = reader.GetValue(0).ToString();
datastring = book.ToCharArray();

How does that work ? He wants to read a random value from the DB. This will give him a useless random number, and he will alway end up with the last string in the data base as his selected string.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

nagendrathecoder2-Oct-09 23:08

2-Oct-09 23:08

Oh yes, i didn't thought abt it. Confused | :confused:

You are rite CG, thanks for telling me.

linto_112-Oct-09 23:10

2-Oct-09 23:10

nagendrathecoder wrote:

I have doubts on following line:
datastring = book.ToCharArray();
R u sure, this line work?

ANS: Actually "datastring = book.ToCharArray();" this line of code works.....the thing is that i have to randomly select a name from the database and display it on a txtbox....that is wt i was doin....but that code snippet of mine was of no use....the snippet which u hav given me does not take d name randomly.....suggest me how to take names randomly from d database???

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Christian Graus2-Oct-09 23:12