I have adapted the C# code from
http://msdn.microsoft.com/msdnmag/issues/03/08/DataGrids/default.aspx for a
data grid combo box column and added it to my data grid. I don't get an
error but the column is simply not displayed (but if I query
VisibleColumnCount I get 7, which means it *should* be there, the row height
is also visibly larger). Can anybody spot what I might be missing/doing
wrong? TIA.
// init
ts := DataGridTableStyle.Create;
dc1 := DataGridTextBoxColumn.Create;
dc2 := DataGridBoolColumn.Create;
dc3 := DataGridTextBoxColumn.Create;
dc4 := DataGridTextBoxColumn.Create;
dc5 := DataGridTextBoxColumn.Create;
dc6 := DataGridTextBoxColumn.Create;
dc7 := DataGridComboBoxColumn.Create;
ts.MappingName := 'ODM';
ts.AlternatingBackColor := color.WhiteSmoke;
// column 1 - ordinary text box:
dc1.MappingName := 'fld_odmID';
dc1.HeaderText := 'ID';
dc1.Alignment := HorizontalAlignment.left;
dc1.NullText := '';
dc1.Width := 45;
<snip - columns 2 - 6 are all text boxes>
// column 7 - the combo box:
SetLookupBinding(dc7.Combobx, 'fld_LastName', 'fld_ContactID',
ds.Tables['contact']); //see procedure below
dc7.HeaderText := 'Ansprechpartner';
dc7.Alignment := horizontalalignment.Left;
dc7.NullText := '';
dc7.Width := 150;
ts.PreferredRowHeight := dc7.Combobx.Height + 1;
ts.GridColumnStyles.Add(dc1);
ts.GridColumnStyles.Add(dc3);
ts.GridColumnStyles.Add(dc4);
ts.GridColumnStyles.Add(dc5);
ts.GridColumnStyles.Add(dc2);
ts.GridColumnStyles.Add(dc6);
ts.GridColumnStyles.add(dc7);
datagrid1.TableStyles.Add(ts);
procedure SetLookupBinding(combobx: System.Windows.Forms.Combobox;
DisplayColumn, BoundColumn: string; dt: DataTable);
begin
with combobx do
begin
DisplayMember := DisplayColumn;
ValueMember := BoundColumn;
DataSource := dt;
end;
end;
and the new class in a separate unit:
unit DataGridComboBoxColumnU;
interface
uses
System.Windows.Forms, System.Drawing, System.Data;
type
DataGridComboBoxColumn = class(System.Windows.Forms.DataGridTextBoxColumn)
private
{ Private-Deklarationen }
cm: CurrencyManager;
intCurrentRow: Integer;
cbb: Combobox; // Hosted combobox control
procedure comboBox_Leave(sender: System.Object; e: EventArgs );
procedure DataGrid_Scroll(sender: System.Object; e: EventArgs);
protected
procedure Edit(source: System.Windows.Forms.CurrencyManager;
rowNum: Integer; bounds: System.Drawing.Rectangle; readOnly: Boolean;
instantText: string; cellIsVisible: Boolean); override;
function GetColumnValueAtRow(source:
System.Windows.Forms.CurrencyManager;
rowNum: Integer): System.Object; override;
procedure SetColumnValueAtRow(source:
System.Windows.Forms.CurrencyManager;
rowNum: Integer; value: System.Object); override;
public
constructor Create;
function Combobx: Combobox;
end;
implementation
constructor DataGridComboBoxColumn.Create;
{Constructor - create combobox, register selection change event handler,
register lose focus event handler}
begin
inherited Create;
// Create combobox and force DropDownList style:
cbb := Combobox.Create;
cbb.DropDownStyle := ComboBoxStyle.DropDownList;
// Add event handler for notification when combobox loses focus:
Include(Self.cbb.Leave, Self.comboBox_Leave);
end;
function DataGridComboBoxColumn.Combobx: Combobox;
begin
Result := cbb;
end;
procedure DataGridComboBoxColumn.comboBox_Leave(sender: System.Object; e:
EventArgs );
{On combobox losing focus, set the column value, hide the combobox,
and unregister scroll event handler}
var
str: string;
rowView: DataRowView;
begin
rowView := DataRowView(cbb.SelectedItem);
str := string(rowView.Row[cbb.DisplayMember]);
SetColumnValueAtRow(cm, intCurrentRow, str);
Invalidate;
cbb.Hide;
Exclude(DataGridTableStyle.DataGrid.Scroll, DataGrid_Scroll);
end;
procedure DataGridComboBoxColumn.Edit(source:
System.Windows.Forms.CurrencyManager;
rowNum: Integer; bounds: System.Drawing.Rectangle; readOnly: Boolean;
instantText: string; cellIsVisible: Boolean);
// On edit, add scroll event handler, and display combobox
var rect: Rectangle;
begin
inherited Edit(source, rowNum, bounds, readOnly, instantText,
cellIsVisible);
if (not readOnly and cellIsVisible) then
begin
// Save current row in the DataGrid and currency manager
// associated with the data source for the DataGrid
intCurrentRow := rowNum;
cm := source;
// Add event handler for DataGrid scroll notification
include(DataGridTableStyle.DataGrid.Scroll, DataGrid_Scroll);
// Site the combobox control within the current cell
cbb.Parent := TextBox.Parent;
rect := DataGridTableStyle.DataGrid.GetCurrentCellBounds;
cbb.Location := rect.Location;
cbb.Size := Size.Create(TextBox.Size.Width, cbb.Size.Height);
// Set combobox selection to given text
cbb.SelectedIndex := cbb.FindStringExact(TextBox.Text);
// Make the combobox visible and place on top textbox control
cbb.Show;
cbb.BringToFront;
cbb.Focus;
end;
end;
function DataGridComboBoxColumn.GetColumnValueAtRow(
source: System.Windows.Forms.CurrencyManager; rowNum: Integer):
System.Object;
{Given a row, get the value member associated with a row. Use the
value member to find the associated display member by iterating
over bound data source}
var
obj: System.&Object;
dv: DataView;
i: Integer;
begin
// Given a row number in the DataGrid, get the display member
obj := inherited GetColumnValueAtRow(source, rowNum);
// Iterate through the data source bound to the ColumnComboBox
cm :=
CurrencyManager(DataGridTableStyle.DataGrid.BindingContext[cbb.DataSource]);
// Assumes the associated DataGrid is bound to a DataView or
// DataTable
dv := DataView(cm.List);
for i := 0 to dv.Count - 1 do
if (obj.Equals(dv[i][cbb.ValueMember])) then
break;
// If set item was found return corresponding value,
// otherwise return DbNull.Value
if (i < dv.Count) then
Result := dv[i][cbb.DisplayMember];
Result := DBNull.Value;
end;
procedure DataGridComboBoxColumn.SetColumnValueAtRow(
source: System.Windows.Forms.CurrencyManager; rowNum: Integer;
value: System.Object);
{Given a row and a display member, iterate over bound data source to
find the associated value member. Set this value member.}
var
s: System.&Object;
dv: DataView;
i: Integer;
begin
s := value;
// Iterate through the data source bound to the ColumnComboBox:
cm := CurrencyManager(
DataGridTableStyle.DataGrid.BindingContext[cbb.DataSource]);
// Assumes the associated DataGrid is bound to a DataView or
// DataTable
dv := DataView(cm.List);
for i := 0 to dv.Count - 1do
if (s.Equals(dv[i][cbb.DisplayMember])) then
break;
if i < dv.Count then
s := dv[i][cbb.ValueMember]
else
s := DBNull.Value;
inherited SetColumnValueAtRow(source, rowNum, s);
end;
procedure DataGridComboBoxColumn.DataGrid_Scroll(sender: System.Object; e:
EventArgs);
// On DataGrid scroll, hide the combobox
begin
cbb.Hide;
end;
end.
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