Implementing Master/Detail for Custom Objects with DataGridViewComboBoxColumns
Imagine you have the following two classes:
public class Parent {
private int id;
private string name;
public Parent( int id, string name ) {
this.id = id;
this.name = name;
}
public int Id {
get { return this.id; }
}
public string Name {
get { return this.name; }
}
}
public class Child : Parent {
private int parentId;
public Child( int id, int parentId, string name )
: base( id, name ) {
this.parentId = parentId;
}
public int ParentId {
get { return this.parentId; }
}
}
private int id;
private string name;
public Parent( int id, string name ) {
this.id = id;
this.name = name;
}
public int Id {
get { return this.id; }
}
public string Name {
get { return this.name; }
}
}
public class Child : Parent {
private int parentId;
public Child( int id, int parentId, string name )
: base( id, name ) {
this.parentId = parentId;
}
public int ParentId {
get { return this.parentId; }
}
}
In the first ComboBoxColumn you display a list of possible Parents. In the second ComboBoxColumn you display Children, but only those that belong to the Chosen Parent. Here is how it goes:
public partial class Form1 : Form {
private Object selectedValue;
public Form1() {
InitializeComponent();
// Add a couple of Parents
for ( int i = 0; i < 3; ++i ) {
Parent parent = new Parent( i, String.Format( "Parent{0:00}", i ) );
this.Column1.Items.Add( parent );
// Add a couple of Children to each parent
for ( int j = 0; j < 5; ++j ) {
Child child = new Child( j, i, String.Format( "Child{0:00}", i * 10 + j ) );
this.Column2.Items.Add( child );
}
}
this.Column1.DisplayMember = "Name";
this.Column2.DisplayMember = "Name";
}
private void dataGridView1_CellParsing( object sender, DataGridViewCellParsingEventArgs e ) {
e.Value = this.selectedValue;
e.ParsingApplied = true;
}
private void dataGridView1_EditingControlShowing( object sender, DataGridViewEditingControlShowingEventArgs e ) {
ComboBox cb = e.Control as ComboBox;
if ( cb != null ) {
// remove all the children that do not belong to the choosen parent
int currentColumnIndex = this.dataGridView1.CurrentCell.ColumnIndex;
if ( currentColumnIndex == 1 ) {
cb.Items.Clear();
int currentRowIndex = this.dataGridView1.CurrentCell.RowIndex;
Object currentCellValue = this.dataGridView1.Rows[currentRowIndex].Cells[0].Value;
if ( currentCellValue != null ) {
int parentId = ( (Parent)currentCellValue ).Id;
foreach ( Child child in this.Column2.Items ) {
if ( child.ParentId == parentId ) {
cb.Items.Add( child );
}
}
}
}
cb.SelectedIndexChanged -= cb_SelectedIndexChanged;
cb.SelectedIndexChanged += cb_SelectedIndexChanged;
}
void cb_SelectedIndexChanged(object sender, EventArgs e) {
ComboBox comboBox = sender as ComboBox;
this.selectedValue = comboBox.SelectedItem;
}
}
private Object selectedValue;
public Form1() {
InitializeComponent();
// Add a couple of Parents
for ( int i = 0; i < 3; ++i ) {
Parent parent = new Parent( i, String.Format( "Parent{0:00}", i ) );
this.Column1.Items.Add( parent );
// Add a couple of Children to each parent
for ( int j = 0; j < 5; ++j ) {
Child child = new Child( j, i, String.Format( "Child{0:00}", i * 10 + j ) );
this.Column2.Items.Add( child );
}
}
this.Column1.DisplayMember = "Name";
this.Column2.DisplayMember = "Name";
}
private void dataGridView1_CellParsing( object sender, DataGridViewCellParsingEventArgs e ) {
e.Value = this.selectedValue;
e.ParsingApplied = true;
}
private void dataGridView1_EditingControlShowing( object sender, DataGridViewEditingControlShowingEventArgs e ) {
ComboBox cb = e.Control as ComboBox;
if ( cb != null ) {
// remove all the children that do not belong to the choosen parent
int currentColumnIndex = this.dataGridView1.CurrentCell.ColumnIndex;
if ( currentColumnIndex == 1 ) {
cb.Items.Clear();
int currentRowIndex = this.dataGridView1.CurrentCell.RowIndex;
Object currentCellValue = this.dataGridView1.Rows[currentRowIndex].Cells[0].Value;
if ( currentCellValue != null ) {
int parentId = ( (Parent)currentCellValue ).Id;
foreach ( Child child in this.Column2.Items ) {
if ( child.ParentId == parentId ) {
cb.Items.Add( child );
}
}
}
}
cb.SelectedIndexChanged -= cb_SelectedIndexChanged;
cb.SelectedIndexChanged += cb_SelectedIndexChanged;
}
void cb_SelectedIndexChanged(object sender, EventArgs e) {
ComboBox comboBox = sender as ComboBox;
this.selectedValue = comboBox.SelectedItem;
}
}
works good, very unique approach! never realized you could have items in the cell that were different from the combobox.
in the Form constructor add
this.Column1.ValueMember = “Id”;
and in
private void dataGridView1_EditingControlShowing
replace
int parentId = ( (Parent)currentCellValue ).Id;
with
int parentId = (int)currentCellValue;
November 8th, 2006 at 03:49
Hi Tim,
It is very good code, but it is not working when tried it with my classes. It shows error like Formatting/Displaying. Why?
Could you please help me.
September 23rd, 2007 at 11:33
hi
how use this code in vb.net with dataset
please help me
October 13th, 2008 at 22:36