same return types ? DataSet & SqlDataReader

[Adie]

Hi, is this not possible?

public DataSet getDimensions()
{
}

public SqlDataReader getDimensions()
{
}

I get this error on compile: "Class 'ProductFamily' already defines a
member called 'getDimensions' with the same parameter types"

-- Doesnt seem right to me --

 

[Jon Skeet [C# MVP]]

Hi, is this not possible?
No.

public DataSet getDimensions()
{
}

public SqlDataReader getDimensions()
{
}

I get this error on compile: "Class 'ProductFamily' already defines a
member called 'getDimensions' with the same parameter types"

-- Doesnt seem right to me --

Why not? Which would you expect to be called in this case:

object o = getDimensions();

or even just

getDimensions();

?

 

[Adie]

Why not? Which would you expect to be called in this case:

object o = getDimensions();

or even just

getDimensions();

I was under the impression that I could overload on return type

DataSet ds = getDimensions()
SqlDataReader dr = getDimensions()

 

[Jon Skeet [C# MVP]]

I was under the impression that I could overload on return type

DataSet ds = getDimensions()
SqlDataReader dr = getDimensions()

No, you can't.

 

[Adie]

No, you can't.

Heh, yes now I know.

Jon, have you ever seen this error with respect to gatagrid and a dataset?

"Cannot create a child list for field dimensions."

Zero mention on google.

 

[Adie]

Heh, yes now I know.

Jon, have you ever seen this error with respect to gatagrid and a dataset?

"Cannot create a child list for field dimensions."

Zero mention on google.

Ok forget that, I seem to have got it working.

 

[Jon Skeet [C# MVP]]

Jon, have you ever seen this error with respect to gatagrid and a dataset?

"Cannot create a child list for field dimensions."

Zero mention on google.

Can't say I've ever seen it. What were you trying to do at the time?

 

[Adie]

Can't say I've ever seen it. What were you trying to do at the time?

Ok, this is the error "Cannot create a child list for field [DataSetName]"
which I called "dimensions". I was trying to bind that dataset to the grid,
like this:

DataSet ds = product.getDataSetDimensions();
_DataGrid = new DataGrid();
_Form.Controls.Add(_DataGrid);

// this commented out code works
//// DataTable dt = ds.Tables[0];
//// _DataGrid.DataSource = dt;

// this causes the error
_DataGrid.SetDataBinding(ds,"dimensions");

I think I need to spend more time reading up on the controls and ADO.

 

[Jon Skeet [C# MVP]]

Ok, this is the error "Cannot create a child list for field [DataSetName]"
which I called "dimensions". I was trying to bind that dataset to the grid,
like this:

DataSet ds = product.getDataSetDimensions();
_DataGrid = new DataGrid();
_Form.Controls.Add(_DataGrid);

// this commented out code works
//// DataTable dt = ds.Tables[0];
//// _DataGrid.DataSource = dt;

// this causes the error
_DataGrid.SetDataBinding(ds,"dimensions");

I think I need to spend more time reading up on the controls and ADO.

Hmm... not sure then, I'm afraid. The table in the dataset is
definitely called dimensions?

 

[Adie]

Ok, this is the error "Cannot create a child list for field [DataSetName]"
which I called "dimensions". I was trying to bind that dataset to the grid,
like this:

DataSet ds = product.getDataSetDimensions();
_DataGrid = new DataGrid();
_Form.Controls.Add(_DataGrid);

// this commented out code works
//// DataTable dt = ds.Tables[0];
//// _DataGrid.DataSource = dt;

// this causes the error
_DataGrid.SetDataBinding(ds,"dimensions");

I think I need to spend more time reading up on the controls and ADO.

Hmm... not sure then, I'm afraid. The table in the dataset is
definitely called dimensions?

Right, well this's where I may be confused. When I created the DataSet I
just called it "dimensions" instead of the actual table name. Maybe this is
why referring to the table via the index works. I thought I could use the
name as a sort of tag or alias being a query can span more than one table.

Here's the jist of what I did:

class GenericData
{
// helper class that allows me to query and add
// any name
public DataSet getDataSetByString(string sql, string dataSetName)
{
SqlConnection mySQLCon = new SqlConnection(@"####");
SqlDataAdapter myAdapter = new SqlDataAdapter();
mySQLCon.Open();
SqlCommand myCommand = new SqlCommand(sql, mySQLCon);
myCommand.CommandType = CommandType.Text;
myAdapter.SelectCommand = myCommand;
DataSet ds = new DataSet(dataSetName); // name the dataset here
myAdapter.Fill(ds);
return ds;
}
}

class ProductFamily
{
public DataSet getDataSetDimensions()
{
GenericData sqlGD = new GenericData();
if (_productType != "")
{
return sqlGD.getDataSetByString(@"SELECT "
+ dimensionArrayToString() + // holds an array of fields for the product
" FROM products WHERE [Product Line] = '"
+ _productType + "' ORDER BY [Product Id];",
"dimensions"); // <-- DataSetName named here on the function call
}
else
{
return sqlGD.returnDataSetNull(); // jiggery pokery, returns a null
// to test against
}
}
}

class DataFormatter
{
public DataFormatter (Form form)
{
_Form = form;
}
public formatProductData(ProductFamily product)
{
DataSet ds = product.getDataSetDimensions();
_DataGrid = new DataGrid();
_Form.Controls.Add(_DataGrid);
DataTable dt = ds.Tables[0];
_DataGrid.DataSource = dt;
}
}

It's basically the fallout from a conversation I had with you a while back
on how to treat products in a database which have a variety of different
attributes, such as width, height, lenght, etc x 100.

I opted for the "wide table" you said you had seperate tables for each
product type/family -- now I spend my time working out how to dynamically
update and display the product data.

 

[Jon Skeet [C# MVP]]

Right, well this's where I may be confused. When I created the DataSet I
just called it "dimensions" instead of the actual table name.

Hang on a sec - there's a big difference between a DataSet and a
DataTable. A DataSet is a *collection* of tables - and in your binding,
you're saying to find the table called "dimensions" within the DataSet.

Maybe this is

why referring to the table via the index works. I thought I could use the
name as a sort of tag or alias being a query can span more than one table.

Here's the jist of what I did:

class GenericData
{
// helper class that allows me to query and add
// any name
public DataSet getDataSetByString(string sql, string dataSetName)
{
SqlConnection mySQLCon = new SqlConnection(@"####");
SqlDataAdapter myAdapter = new SqlDataAdapter();
mySQLCon.Open();
SqlCommand myCommand = new SqlCommand(sql, mySQLCon);
myCommand.CommandType = CommandType.Text;
myAdapter.SelectCommand = myCommand;
DataSet ds = new DataSet(dataSetName); // name the dataset here
myAdapter.Fill(ds);
return ds;
}
}

Ah - that will have created a table called "Table", I believe.

I personally use data adapters to fill tables, and add those tables to
DataSets separately. So, I'd use:

DataTable table = new DataTable("dimensions");
myAdapter.Fill(table);
ds.Tables.Add(table);

I find this a bit easier to manage.

It's basically the fallout from a conversation I had with you a while back
on how to treat products in a database which have a variety of different
attributes, such as width, height, lenght, etc x 100.

Ah, right. Don't remember that off-hand, I'm afraid, but hopefully the
above will help you.

 

[Chris Baldwin]

Hi, is this not possible?

public DataSet getDimensions()
{
}

public SqlDataReader getDimensions()
{
}

The compiler is correct. It is not possible. You need to provide
different parameters in order to overload the methods.

-Chris

 

[Adie]

I personally use data adapters to fill tables, and add those tables to
DataSets separately. So, I'd use:

DataTable table = new DataTable("dimensions");
myAdapter.Fill(table);
ds.Tables.Add(table);

I find this a bit easier to manage.

Yeah, I can see that's a little more transparent.

Ah, right. Don't remember that off-hand, I'm afraid, but hopefully the
above will help you.

Well I found another way of tackling the problem, but yes, as *always*,
helpful, thanks.

 

[Adie]

The compiler is correct. It is not possible. You need to provide
different parameters in order to overload the methods.

I don't know why I thought it different than C++, moment of madness I
guess.