C# Discussion Boards - CodeProject

21-Jul-05 9:02

I'm putting together my first C# database application. It compiles fine and seems to be connecting to my database fine, but when I create the command I get the following error:

An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in system.data.dll

This is the line VS claims is causing the error:
this.cmdGetNewClients = new System.Data.OleDb.OleDbCommand();

The code around it is:

this.cn.Open();
this.cmdGetNewClients = new System.Data.OleDb.OleDbCommand();
cmdGetNewClients.CommandText = @"SELECT ClientName FROM Clients";
cmdGetNewClients.Connection = this.cn;
OleDbDataReader rdr = cmdGetNewClients.ExecuteReader();
while(rdr.Read())
newClients.Add(rdr["[Client Name]"]);
rdr.Close();
cn.Close();

Can anyone tellme why I'm getting this error and how to fix it?\

Thanks!

The ends can never justify the means. It is the means that determine the ends.

squawk21-Jul-05 9:12

21-Jul-05 9:12

The error is too general. Wrap the code in a try catch block and see what the true error is.
If you catch and exception of type SqlException you can try this:
foreach(SqlError err in sqlEx.Errors)
Console.Writeline(e.Message);
Otherwise just check the InnerException. It could be something simple like a login issue.

theStorminMormon21-Jul-05 9:23

21-Jul-05 9:23

Thanks for the advice, can you give me a hand writing the try/catch though? I'm afraid I'm a bit new to C# and rusty in the other stuff I knew in college.

it would go something like this:

try
{
this.cmdGetNewClients = new System.Data.OleDb.OleDbCommand();
}
catch()
{
foreach(SqlError err in sqlEx.Errors)
console.WriteLine(e.Message);
}

What goes in the catch()?

Thanks so much for helping.

The ends can never justify the means. It is the means that determine the ends.

squawk21-Jul-05 9:31

21-Jul-05 9:31

Try something like this:
try
{
//insert your code here
}
catch(OleDbException ex)
{
Console.WriteLine("Message: " + ex.Message + "\n");
if(ex.InnerException != null)
Console.WriteLine("Message: " + ex.InnerException.Message + "\n");
foreach(OleDbError e in ex.Errors)
Console.WriteLine(e.Message + "\n");
}

theStorminMormon21-Jul-05 9:41

21-Jul-05 9:41

OK, I got that coded in, but it doesn't seem to be actually catching the error. It's highlighting the lind of code inside the try, but it's still saying it's an "unhandled exception" and I'm not getting any console output.

What gives now?

The ends can never justify the means. It is the means that determine the ends.

Rob Graham21-Jul-05 9:42

Rob Graham

21-Jul-05 9:42

Possibly a typo in your post, but...
you select a field named [ClientName] (no space)
then try to get the field value from [Client Name] (space btwn Client & Name)
no such field exists in the readr, so an exception is thrown.

Absolute faith corrupts as absolutely as absolute power
Eric Hoffer
The opposite of the religious fanatic is not the fanatical atheist but the gentle cynic who cares not whether there is a god or not.
Eric Hoffer

theStorminMormon21-Jul-05 9:46

21-Jul-05 9:46

Thanks for spotting that. It was actually an error in the code (I'd renamed the field and forgotten to update all references to it), but it's not causing the error. The code doesn't even get that far.

The ends can never justify the means. It is the means that determine the ends.

squawk21-Jul-05 10:01

21-Jul-05 10:01

I took your code and for the most part is worked ok. I filled in some of the blanks and got this code to complie and run:

OleDbConnection cn = new OleDbConnection("User ID=xxx;Password=xxx;Initial Catalog=Northwind;Data Source=192.168.0.1;Provider=SQLOLEDB");
cn.Open();
System.Data.OleDb.OleDbCommand cmdGetNewClients = new System.Data.OleDb.OleDbCommand();
cmdGetNewClients.CommandText = @"SELECT LastName FROM Employees";
cmdGetNewClients.Connection = cn;
OleDbDataReader rdr = cmdGetNewClients.ExecuteReader();
ArrayList newClients = new ArrayList();
while(rdr.Read())
newClients.Add(rdr["LastName"]); <-- change made here
rdr.Close();
cn.Close();

Good luck.

refresh form from another form

Luis Alonso Ramos21-Jul-05 10:40

Luis Alonso Ramos

21-Jul-05 10:40

Maybe you are forgetting to set the connection string in the OleDbConnection object.

-- LuisR

Luis Alonso Ramos
Intelectix - Chihuahua, Mexico

Not much here: My CP Blog!

webhay21-Jul-05 8:35

webhay

21-Jul-05 8:35

Hello All,

I Lunch a form from another form how can i refresh the Firest form after I click button on the second form.

Regards
Hay

Re: refresh form from another form

Piovra_21-Jul-05 21:32

Piovra_

21-Jul-05 21:32

if you launch the second form from the first one you can add the first form in de constructor of the second. Something like

private Form m_form1<br />
<br />
public Form2(Form form1)<br />
{<br />
  m_form1 = form1<br />
}<br />
<br />
your button click would be someting like:<br />
<br />
<code>private void HandleClick()<br />
{<br />
  m_form1.Refresh();<br />
}<br />
<br />
basically you can call any public method in form1.<br />
<br />
Other more advanced option is to use the observer pattern. You can google for observer and c# to get more info on that subject.<br />
<br />
<br />

DataGrid question

zaboboa21-Jul-05 7:48

zaboboa

21-Jul-05 7:48

Hello,

I have a datagrid:

this.dataGridRevenues.DataMember = "LotYields";
this.dataGridRevenues.DataSource = this.dataset;

is there a way to display only certain rows in the grid, when loading the
dataset?

Thank you.

Re: DataGrid question

Alomgir Miah21-Jul-05 8:02

Alomgir Miah

21-Jul-05 8:02

Try this

this.dataset.Tables("Products").Columns("Name").ColumnMapping = MappingType.Hidden

Alomgir Miah
Live Life King Size

Re: DataGrid question

squawk21-Jul-05 9:05