ComboBox.ValueMember and DisplayMember

Question

How do i set this values? I have a DataTable with all the data i want to set in the combobox, but i cant find how to set it.

I tried

ComboBox1.DataSource = dataTable;
ComboBox1.ValueMember = "id"; // --> once hes here, he just jumps out the method
ComboBox1.DisplayMember = "name";

No compilation error, warning, nothing.. just jumps out!

This is the query to fill the DataTable

"Select * from \"Table\""

I checked with the debugger and the datatable was filled. The columns names are "id" and "name". ComboBox is blank. I'm filling it for the first time!

Answer 1

Using keyvalue pairs to populate a combobox

A neat way to populate combo boxes is to set the datasource to a list of keyvalue pairs. It may also inspire using data stored in a list of some kind:

//Some values to show in combobox
string[] ports= new string[3] {"COM1", "COM2", "COM3"};

//Set datasource to string array converted to list of keyvaluepairs
combobox.Datasource = ports.Select(p => new KeyValuePair<string, string>(p, p)).ToList();

//Configure the combo control
combobox.DisplayMember = "Key";
combobox.ValueMember = "Value";
combobox.SelectedValue = ports[0];

The datasource can be populated using this syntax as well:

ports.Select(p => new { Key = p, Value = p }).ToList();

The technicue may be expanded with more property names for multiple column lists.

Answer 2

You should not set datasource of your listbox and/or combobox in this order

ComboBox1.DataSource = dataTable;

ComboBox1.ValueMember = "id"; 

ComboBox1.DisplayMember = "name";

Instead, this is correct order:

ComboBox1.ValueMember = "id"; 

ComboBox1.DisplayMember = "name";

ComboBox1.DataSource = dataTable;

NOTE: setting datasource should be last line.

If you set datasource first, SelectedIndexChanged event will fire and you may get the cast error or other exception.