Re: Dataset retunring Null ..a guru's opinion required!

When I invoke the service i now get this error:

System.InvalidOperationException: Fill: SelectCommand.Connection property
has not been initialized.
at System.Data.Common.DbDataAdapter.GetConnection3(DbDataAdapter adapter,
IDbCommand command, String method)
at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset,
DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable,
IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32
startRecord, Int32 maxRecords, String srcTable, IDbCommand command,
CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable)

I initialised the adapter by doing this:

Dim str As String = "SELECT EstateAgents.*.* FROM EstateAgents"

Dim estateOleAdapter As New OleDbDataAdapter(str, estateOleConnection)

But that didn't help.

I initialised the adapter:

at WebServiceLiverpoolUKEstateAgents.Service1.GetEstateAgents() in
C:\Hope\modules i teach\web services\handout
exercises\chapter5\WebServiceLiverpoolUKEstateAgents
-
UK


"Patrice" wrote:

How is estateOleAdapter initialized ?

My guess is that this is Nothing so you have a null reference exception when
you call this web method...

--
Patrice

"Nab" <Nab@xxxxxxxxxxxxxxxxxxxxxxxxx> a crit dans le message de groupe de
discussion : 449A6931-B77A-474D-B7F2-5659D0641B2F@xxxxxxxxxxxxxxxx
I hope someone could shed some light on this issue. Is this relating to
some
"bug" in Visual Basic 2008 or am I doing something wrong here? I have
established a connection to a Microsoft Access database using the GUI
e.g. dragging the OleDbConnection icon on the
toolbox to the design area to establish the connection (i.e. not in code).
This process creates a connection object and an OleDbAdapter object (which
I
named estateOleAdapter as you can see in my web service's code):

<WebMethod()> _
Public Function GetEstateAgents() As DataSet
Dim estateDataset As DataSet = New DataSet
estateOleAdapter.Fill(estateDataset, "EstateAgents")
Return estateDataset
estateOleConnection.Close()
End Function

I also tried
to establish the connection and adapter in code but continue to have the
same
problem.

Whenever I try to consume this service (using a web or even a windows
application this exception comes up):

System.ServiceModel.FaultException was unhandled by user code
Message="System.Web.Services.Protocols.SoapException: Server was unable
to
process request. ---> System.NullReferenceException: Object reference not
set
to an instance of an object. at
WebServiceLiverpoolUKEstateAgents.Service1.GetEstateAgents() in
C:\Hope\modules i teach\web services\handout
exercises\chapter5\WebServiceLiverpoolUKEstateAgents\WebServiceLiverpoolUKEstateAgents\LiverpoolUKEstateAgents.asmx.vb:line
29 --- End of inner exception stack trace ---"
Source="mscorlib"
StackTrace:
Server stack trace: at
System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime
operation, ProxyRpc& rpc) at
System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean
oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs,
TimeSpan timeout) at
System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean
oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
at
System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage
methodCall, ProxyOperationRuntime operation) at
System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]: at
System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage
reqMsg, IMessage retMsg) at
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&
msgData,
Int32 type) at
ClientLiverpoolUKEstateAgents.WebServiceLiverpoolUKEstateAgents.Service1Soap.GetEstateAgents()
at
ClientLiverpoolUKEstateAgents.WebServiceLiverpoolUKEstateAgents.Service1SoapClient.GetEstateAgents()
in C:\Hope\modules i teach\web services\handout
exercises\chapter5\ClientLiverpoolUKEstateAgents\ClientLiverpoolUKEstateAgents\Service
References\WebServiceLiverpoolUKEstateAgents\Reference.vb:line 59 at
ClientLiverpoolUKEstateAgents._Default.form1_Load(Object sender, EventArgs
e)
in C:\Hope\modules i teach\web services\handout
exercises\chapter5\ClientLiverpoolUKEstateAgents\ClientLiverpoolUKEstateAgents\Default.aspx.vb:line
19 at System.Web.UI.Control.OnLoad(EventArgs e) at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint,
Boolean includeStagesAfterAsyncPoint)
InnerException:

This is the code (inserted in a command's click procedure) that I used to
consume the service:

Dim eaService As New WebServiceLiverpoolUKEstateAgents.Service1SoapClient

'Supply the dataset to become the DataGrid's datasource
'dgEstateAgents.DataSource = eaService.GetEstateAgents

dgEstateAgents.DataSource = eaService.GetEstateAgents

'Bind the data to the datagrid by transferring
'it from the dataset to the datagrid

dgEstateAgents.DataBind()

The dgEstateAgents is the name of the datagrid which I created using the
GUI. When adding a reference, I tried "Add Service Reference" and I also
tried "Add Web Reference", neither worked.

To ensure that my web service is well connected to my Access database, I
would sometimes click on the Data icon on the menu bar and select Preview
Data and then click to populate the dataset. Sometimes this results in
the
display of the database's table. However, when I try to do same thing
other
times I get a window that says: "Value cannot be null. Parameter name:
serviceProvider" which leads me to conclude that the dataset is empty. If
I
close that web service and relaunch it I don't get this "Value cannot be
null. Parameter name: serviceProvider" error!!


In either case, my client application halts on this line
dgEstateAgents.DataSource = eaService.GetEstateAgents
every time I try to consume the service and throws the exception listed
above.

The operation system I use is Vista (business edition).

When I used VS 2005 in the past I had no such errors and the web service
was
consumed without any problems. So, I am really clueless here!





--
UK


.

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