CODEWITHSUNDEEP
c#.netdata-bindingcombobox
bmt22033
bmt22033

Reputation: 7240

Changing datasource dynamically?

I have a WinForms combobox that is bound to a list of objects list this:

BindingList<myObject> myListOfObjects = new BindingList<myObject>();

// 100 objects are added to myListOfObjects

bindingSource1.DataSource = myListOfObjects;
comboBox1.DataSource = bindingSource1;
comboBox1.DisplayMember = "Name";

Each instance of my object contains the following:

public string Name
public int Index
public List<int> Codes = new List<int>();

The object also implements INotifyPropertyChanged.

When an objects "Name" is selected in the combobox, I want to databind a listbox to the "Codes" list for the selected object. I'm trying to do this as such:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    listBox1.DataSource = myListOfObjects[((myObject)comboBox1.SelectedValue).Index].Codes;
}

This doesn't work and I get an InvalidCastException (specifically that Int32 can't be cast as myObject). Am I going about this all wrong?

Upvotes: 1

Views: 186

Answers (1)

competent_tech
competent_tech

Reputation: 44931

The problem is that combobox1.SelectedValue will be set to the myObject property that is specified in the ValueMember of the combobox.

In order to get the underlying myObject, you need to use comboBox1.SelectedItem:

listBox1.DataSource = myListOfObjects[((myObject)comboBox1.SelectedItem).Index].Codes;

If this were my code, I would also double-check to ensure that SelectedItem is not null before using it directly:

if (comboBox1.SelectedItem != null) {
    listBox1.DataSource = myListOfObjects[((myObject)comboBox1.SelectedItem).Index].Codes;
} else {
    listBox1.DataSource = null;
}

Upvotes: 2

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