DataGridView Behaviour

[JoaquimC]

Helo,

I got this problem with a c# DataGridView in VS2005:

The DataGridView has 2 columns: colArtigoGenerico, colArtigoFinal; and this columns are populated with data from 2 columns from a DataTable: "Detalhes".

1st i populate the DataGrid with a Datatable using this code:

string select = "SELECT a.CArtigoGenerico, a.CArtigoFinal " +
"FROM ArtigosGenericos a ORDER BY a.CArtigoGenerico ";
SqlDataAdapter adaptador = new SqlDataAdapter(select, ligacao);
adaptador.Fill(Detalhe, "Detalhes");

// Populate the Grid:
DGV.AutoGenerateColumns = false;
DGV.DataSource = Detalhe.Tables["Detalhes"];

DGV.Columns["colArtigoGenerico"].DataPropertyName = "CArtigoGenerico";
DGV.Columns["colArtigoFinal"].DataPropertyName = "CArtigoFinal";

ColArtigoGenerico.ValueMember = DGV.Columns[0].DataPropertyName;
ColArtigoFinal.ValueMember = DGV.Columns[1].DataPropertyName;

The above code is in a button_click event. And at the 1st time i run it, the grid is populated correctly. Then i set the DataSource to null and the DataGridView, as expected, collapses and shows no record.

Then i click again in the 1st button, and the DataGridView, this time, shows no record.

In a debug session i see that the DataTable has some records, and after the code line:
DGV.DataSource = Detalhe.Tables["Detalhes"];
The DGV.RowCount property returns 0, that's why it shows no record in the Grid.

But the DataTable that is the DataSource for the Grid has 3 records.
Why this behaviour in the 2nd and following times?

TIA,
Joaquim

[Plater]

What is all this buisness?

DGV.Columns["colArtigoGenerico"].DataPropertyName = "CArtigoGenerico";
DGV.Columns["colArtigoFinal"].DataPropertyName = "CArtigoFinal";
 
ColArtigoGenerico.ValueMember = DGV.Columns[0].DataPropertyName;
ColArtigoFinal.ValueMember = DGV.Columns[1].DataPropertyName;
 

If you set auto-generate columns to on, then it will doo of this for you?

I am thinking your troubles are that you are not removing the columns you made when you set the datasource to null?

[JoaquimC]

Thank You Plater:

I didn't mention it, for readability reasons, but the two columns are comboboxes, so i need to set the datasource for each one of the comboboxes and the auto-generate behaviour does not do what i want, because it generates TextBox columns.

About removing columns: is that necessary? Maybe that's the reason for the behaviour, but thinking again: no, because in the 2nd time i run the code i see that the DataGridView has no records and the 1st time it had 3.

Why?

Joaquim

What is all this buisness?

DGV.Columns["colArtigoGenerico"].DataPropertyName = "CArtigoGenerico";
DGV.Columns["colArtigoFinal"].DataPropertyName = "CArtigoFinal";
 
ColArtigoGenerico.ValueMember = DGV.Columns[0].DataPropertyName;
ColArtigoFinal.ValueMember = DGV.Columns[1].DataPropertyName;
 

If you set auto-generate columns to on, then it will doo of this for you?

I am thinking your troubles are that you are not removing the columns you made when you set the datasource to null?

[Plater]

But are you are adding the columns each time? They get all kinds of confused when you have multiple columns with the same name

[JoaquimC]

No i'm not adding the columns each time, they're added automaticaly by VS2005 in the Class.Designer.cs file, and i do not touch them anymore.

And there is no columns with the same name, where did you get that idea?

Joaquim

[Plater]

If you added those columns more then once (some people do that) it confuses it

[JoaquimC]

Thank you Plater.

Meanwile i solved my problem: it was related with a DataTable.Reset() i do between the 1st and 2nd call to the event.

I replaced the reset() with a clear() and now the DataGridView behaves as it should.
I don't understand, though, why the DataGrid was so closely bind to the DataTable that, with no DataBind in code, it reacted to its reset, but, when i populated the Table again, it did not react and show none of its records; instead, if i clear the Table data with the Clear() method, now it shows all the records.
From my point of view there's only one explanation: the Reset() method resets the DataBind also and the Clear() method don't.

Thank you again.
Joaquim