Cannot use ComboBox SelectedItem as BindingSource for cascaded ComboBox - binding

Question

I have 2 ComboBoxes on my form. I create the bindings as follows:
TestClass myclass = new TestClass("Instruments");
myclass.Add(instr1 = new TestClass("INSTR1"));
myclass.Add(instr2 = new TestClass("INSTR2"));
myclass.Add(instr3 = new TestClass("INSTR3"));
myclass.Add(instr4 = new TestClass("INSTR4"));
instr1.Add(app1 = new TestClass("app1"));
instr1.Add(app2 = new TestClass("app2"));
instr1.Add(app3 = new TestClass("app3"));
instr1.Add(app4 = new TestClass("app4"));
instr2.Add(app5 = new TestClass("app5"));
instr2.Add(app6 = new TestClass("app6"));
instr2.Add(app7 = new TestClass("app7"));
instr2.Add(app8 = new TestClass("app8"));
mysource = new BindingSource(myclass, null);
selectedComboBox1.DataSource = mysource;
selectedComboBox1.DisplayMember = "NAME";
mysource2 = new BindingSource(selectedComboBox1, "SelectedItem");
selectedComboBox2.DataSource = mysource2;
selectedComboBox2.DisplayMember = "NAME";
The class used for the binding looks as follows
class TestClass : BindingList<TestClass>, INotifyPropertyChanged
{
public event RunTestChanged RunTestChangedEventHandler;
public TestClass()
{
this.test = "";
this.name = "";
this.runTest = true;
}
public TestClass(string name)
{
this.test = "";
this.name = name;
this.runTest = true;
}
public TestClass LIST
{
get
{
return this;
}
}
public string NAME
{
get
{
return this.name;
}
set
{
this.name = value;
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs("NAME"));
}
}
}
public string TEST
{
get
{
return this.test;
}
set
{
this.test = value;
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs("TEST"));
}
}
}
public bool RUNTEST
{
get
{
return runTest;
}
set
{
runTest = value;
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs("RUNTEST"));
}
RunTestArgs myargs = new RunTestArgs(value);
if (RunTestChangedEventHandler != null)
{
RunTestChangedEventHandler(this, myargs);
}
}
}
private bool runTest;
private string name;
private string test;
public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
}
when the form first loads the 2 comboboxes are filled as they should be with the expected items. However, if i change an item in selectedComboBox1, the items in selectedComboBox2 aren't updated. I know that I can subscribe to the selectedComboBox1 SelectedIndexChanged event and then rebind the DataSource on selectedComboBox2 and everything will work as expected.
For example:
void selectedComboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
mysource2.DataSource = selectedComboBox1.SelectedItem;
mysource2.DataMember = null;
}
Another alternative that works is to perform the databinding as follows:
mysource = new BindingSource(myclass, null);
mysource2 = new BindingSource(mysource, "LIST");
mysource3 = new BindingSource(mysource2, "LIST");
selectedComboBox1.DataSource = mysource;
selectedComboBox1.DisplayMember = "NAME";
selectedComboBox2.DataSource = mysource2;
selectedComboBox2.DisplayMember = "NAME";
However I wanted to know if there was a way to avoid having to subscribe to the event or performing the databinding in a different manner and just have the 2nd ComboBox be updated via the BindingSource using the SelectedItem property. In the end I'm curious to know how to get the BindingSource to be updated via the SelectedItem databinding and if it's not possible what is preventing it from working.
Thank you for your help.

Answer 1

i have the same issue and got resolved by binding Name to SelectedValue of combobox and set ValueMember to be "NAME" property
selectedComboBox1.DisplayMember = "NAME";
selectedComboBox1.ValueMember = "NAME";