Simple database class error

  • Thread starter Thread starter Lasse Edsvik
  • Start date Start date
L

Lasse Edsvik

Hello

Im trying to create a simple testclass that connects to a db on localhost
and a method that returns a dataset. I get these errors:

Unhandled Exception: System.InvalidOperationException: Fill:
SelectCommand.Conne
ction property has not been initialized.
at System.Data.Common.DbDataAdapter.GetConnection3(DbDataAdapter adapter,
IDb
Command command, String method)
at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset,
DataTable[]
datatables, Int32 startRecord, Int32 maxRecords, String srcTable,
IDbCommand co
mmand, 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)
at Procent.DataJox.Northwind.GetAllCustomers() in C:\Documents and
Settings\A
dministrator\My Documents\Visual Studio\Projects\DataJox\DataJox\Class1.cs:
line 21
at rock.Program.Main(String[] args) in C:\Documents and
Settings\Administrato
r\My Documents\Visual Studio\Projects\DataJox\rock\Program.cs:line 14



using System;

using System.Collections.Generic;

using System.Text;

using System.Data;

using System.Data.SqlClient;

namespace Procent.DataJox

{

public class Northwind

{

private SqlConnection dbconn;


public DataSet GetAllCustomers()

{

Open();

DataSet ds = new DataSet();


SqlDataAdapter da = new SqlDataAdapter();

da.SelectCommand = new SqlCommand("CustListAll", dbconn);

da.Fill(ds);

return ds;

}



private void Open()

{

string connstr = "server=localhost;database=northwind;UID=sa;PWD=kk";

try

{

SqlConnection dbconn = new SqlConnection(connstr);

dbconn.Open();

}

catch

{

throw;

}

}


}


}
 
Lasse said:
Im trying to create a simple testclass that connects to a db on localhost
and a method that returns a dataset. I get these errors:

Unhandled Exception: System.InvalidOperationException: Fill:
SelectCommand.Conne
ction property has not been initialized.
Click to expand...

That's because you never open the connection.
Open();
Click to expand...

The connection you open in the Open() method is a /different/
connection that is declared inside the Open method and is only visible
there. It is not the same as the one you declared at class level.
SqlConnection dbconn = new SqlConnection(connstr);
Click to expand...

Change this line to:

dbconn = New SqlConnection(connstr)
 
The line
SqlConnection dbconn = new SqlConnection(connstr);
in the Open method is the problem.
Replace this line with
dbconn = new SqlConnection(connstr);


What's happenning here is that a connection object is being created,
assigned to and opened properly in the Open method. However, this is
being assigned to the local variable dbconn (because of the
SqlConnection dbconn declaration inside the Open method). This local
dbconn variable is valid only within the Open method. The dbconn
variable referred to in the GetAllCustomers method is the private
variable dbconn which has never been assigned to.

Regards,
Sarin.
 
Spidey,

thx, one step further til next error :)

I still get NullReferenceException, but on this line:

da.SelectCommand.Connection = dbconn;

not sure what's wrong here



using System;

using System.Collections.Generic;

using System.Text;

using System.Data;

using System.Data.SqlClient;

namespace Procent.DataJox

{

public class Northwind

{

private SqlConnection dbconn;


public DataSet GetAllCustomers()

{

Open();

DataSet ds = new DataSet();


SqlDataAdapter da = new SqlDataAdapter();

da.SelectCommand.Connection = dbconn;

da.SelectCommand = new SqlCommand("CustListAll");

da.Fill(ds);

return ds;

}



private void Open()

{

string connstr = "server=localhost;database=northwind;UID=sa;PWD=kk";


try

{

dbconn = new SqlConnection(connstr);

dbconn.Open();

}

catch

{

throw;

}

}


}


}




Spidey said:
The line
SqlConnection dbconn = new SqlConnection(connstr);
in the Open method is the problem.
Replace this line with
dbconn = new SqlConnection(connstr);


What's happenning here is that a connection object is being created,
assigned to and opened properly in the Open method. However, this is
being assigned to the local variable dbconn (because of the
SqlConnection dbconn declaration inside the Open method). This local
dbconn variable is valid only within the Open method. The dbconn
variable referred to in the GetAllCustomers method is the private
variable dbconn which has never been assigned to.

Regards,
Sarin.

Lasse said:
Hello

Im trying to create a simple testclass that connects to a db on localhost
and a method that returns a dataset. I get these errors:

Unhandled Exception: System.InvalidOperationException: Fill:
SelectCommand.Conne
ction property has not been initialized.
at System.Data.Common.DbDataAdapter.GetConnection3(DbDataAdapter adapter,
IDb
Command command, String method)
at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset,
DataTable[]
datatables, Int32 startRecord, Int32 maxRecords, String srcTable,
IDbCommand co
mmand, 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)
at Procent.DataJox.Northwind.GetAllCustomers() in C:\Documents and
Settings\A
dministrator\My Documents\Visual Studio\Projects\DataJox\DataJox\Class1.cs:
line 21
at rock.Program.Main(String[] args) in C:\Documents and
Settings\Administrato
r\My Documents\Visual Studio\Projects\DataJox\rock\Program.cs:line 14



using System;

using System.Collections.Generic;

using System.Text;

using System.Data;

using System.Data.SqlClient;

namespace Procent.DataJox

{

public class Northwind

{

private SqlConnection dbconn;


public DataSet GetAllCustomers()

{

Open();

DataSet ds = new DataSet();


SqlDataAdapter da = new SqlDataAdapter();

da.SelectCommand = new SqlCommand("CustListAll", dbconn);

da.Fill(ds);

return ds;

}



private void Open()

{

string connstr = "server=localhost;database=northwind;UID=sa;PWD=kk";

try

{

SqlConnection dbconn = new SqlConnection(connstr);

dbconn.Open();

}

catch

{

throw;

}

}


}


}
Click to expand...
Click to expand...
 
...
thx, one step further til next error :)

I still get NullReferenceException, but on this line:

da.SelectCommand.Connection = dbconn;

not sure what's wrong here
Click to expand...
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand.Connection = dbconn;
da.SelectCommand = new SqlCommand("CustListAll");
Click to expand...

Maybe you should shift the order of statements...

SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = new SqlCommand("CustListAll");
da.SelectCommand.Connection = dbconn;

// Bjorn A
 
Bjorn,

thx very much....... :)

class seem fine now though........ Just cant get it to display in a listbox
or whatever :)

cant get that DataBind to show up for the object im trying to populate.


what's more needed to do besides:

public Form1()

{

InitializeComponent();

Northwind n = new Northwind();

listBox1.DataSource = n.GetAllCustomers();


}
 
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