Datagridview comboboxcolumn Oracle datasource problem

DataGridViewComboBoxColumn comboboxColumn = new DataGridViewComboBoxColumn();
comboboxColumn.DataPropertyName = "RFT_CODE_ID";
comboboxColumn.HeaderText = "RFT";
comboboxColumn.Name = "RFT_CODE_ID";
comboboxColumn.DropDownWidth = 90;
comboboxColumn.Width = 110;
comboboxColumn.MaxDropDownItems = 10;
comboboxColumn.FlatStyle = FlatStyle.Flat;
comboboxColumn.SortMode = DataGridViewColumnSortMode.Automatic;

CodesTable codes = new CodesTableAdapter(Connection).GetCodesByTypeID(525, false);
comboboxColumn.DataSource = codes;

comboboxColumn.ValueMember = codes.CodeIDColumn.ColumnName;
comboboxColumn.DisplayMember = codes.CodeDescriptionColumn.ColumnName;
//comboboxColumn.ReadOnly = true;
dgvRFT.Columns.Add(comboboxColumn);


Codes are as follows
CODE_ID      CODE_DESCRIPTION
1009103      Unsuitable
1009104      Factfind
1009105      Clarify
1009106      Suitability letter/report
1009107      Accept
1009108      Corporate stance not followed
1009300      Return to FC

code_id is number(10), as is the FIRST_TIME_ACCEPTANCE_CODE_ID.

Where do you set Value and Text fields of combobox?

dgvRFT.DataValueFiled="RFT_CODE_ID"
dgvRFT.DataTextField="RFT_CODE_ID" or something different for txt field.

Previous post answers that (posts must  have crossed)

And how are you getting that description from you query? when you use nvl for the ID that's only going to work in that particular column, is not goint to automatically fetch the description associated with that ID.

That's what the combobox does. Or am I being stupid here ?

Your combobox is using a differente query than the one you posted?

It's populated here
CodesTable codes = new CodesTableAdapter(Connection).GetCodesByTypeID(525, false);
comboboxColumn.DataSource = codes;
comboboxColumn.ValueMember = codes.CodeIDColumn.ColumnName;
comboboxColumn.DisplayMember = codes.CodeDescriptionColumn.ColumnName;

The way I understand it is that the combobox dataproperty is used to match against the list of keys that have been defined (as above ). The dataproperty is the value of the underlying cell.
comboboxColumn.DataPropertyName = "RFT_CODE_ID";

When the cell value and key match the associated description is displayed.
As I said before, this works fine for the first case, but not for the other 2.

What DataType is the column tr.FIRST_TIME_ACCEPTANCE_CODE_ID from the query? and what DataType is the column CODE_ID from the ComboBox?

both number(10

Ok, try using this as the value to your query:

", nvl(tr.FIRST_TIME_ACCEPTANCE_CODE_ID, CAST(1009107 AS tr.FIRST_TIME_ACCEPTANCE_CODE_ID%TYPE)) RFT_CODE_ID "

                                              

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Ah ! It appears I haven't made myself clear.
There is a valid value in the underlying data, which displays the correct description in the combobox when I run with the first piece of code.
Using the NVL version stops it displaying correctly, even though the underlying value hasn't changed.

I'll be happy if someone can point me to an alternative solution other than using NVL().
I have also tried this code (attached), but even though the value matches an entry in the combobox datasource, I just get the underlying value displayed in the combobox instead of the description (as it does using the NVL version).

private void dgvRFT_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
	if (e.ColumnIndex == 5) // combobox 
	{
		if (e.Value.ToString().Length == 0)
		{
			e.Value = 1009107;
			dgvRFT.Rows[e.RowIndex].ReadOnly = false;
		}
		else
		{
			dgvRFT.Rows[e.RowIndex].ReadOnly = true;
		}
	}
}
                                              

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Another way to do it is like this, setting the NullValue property when you define the column:

comboboxColumn.DefaultCellStyle.NullValue = "Accept";

                                              

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That displays the combobox correctly when there is a null value, but it doesn't update the underlying cell value.
So when I go to update the database, there is still a null value there.
If I change the combobox selection, a value gets put into the underlying cell, but not for the default.

There's an additional property to control the value of the datasource, try adding this where you define your combobox column:

comboboxColumn.DefaultCellStyle.DataSourceNullValue = 1009107;

                                              

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