Thanks Kevin, but my combobox is still empty. Here's my latest code I tested, but without success:

SqlConnection conn = new SqlConnection (ConfigurationSettings.AppSettings["ConnectionString"]);
DataSet dsTable = new DataSet ();
SqlDataAdapter adptTable = new SqlDataAdapter ("select * from client", conn);
adptTable.Fill (dsTable, "Client");
cboClient.DisplayMember = "Client";
cboClient.ValueMember = "PK_Client";
cboClient.DataSource = dsTable.Tables["Client"];
cboClient.DataBindings.Add ("SelectedValue", dsTable.Tables["Client"], "PK_Client");

>I think you're close...I believe you need one more line at the end, to actually bind/map a property of the combobox to the datatable.

>cboClient.DataBindings.Add("SelectedValue",dtClient, ,"PK_Client");

>This way, what's in the combo's SelectedValue (associated with ValueMember) will be mapped to PK_Client.