无法以编程方式设置 ComboBox 选择

Question

我无法在 ComboBox 中以编程方式设置选择。我尝试设置各种属性（SelectedItem、SelectedText、SelectedIndex），但 ComboBox 不显示名称。ComboBox 的第一行是空白的，被选中。属性设置的返回值是正确的。我究竟做错了什么？...this.bsConstructionContractors.DataSource = typeof(Contractor);...public partial class EditContractorDialog : Form{    public EditContractorDialog(Contractor contractor)    {        InitializeComponent();        this.cmbEditContractorName.DataBindings.Add(new System.Windows.Forms.Binding("SelectedValue", projectView.bsProject, "ContractorId", true));        // new BindingSource is important here, so as to use a separate CurrencyManager        // because bsConstructionContractors is shared with another ComboBox on another form        this.cmbEditContractorName.DataSource = new BindingSource(projectView.bsConstructionContractors, null);        this.cmbEditContractorName.ValueMember = "ContractorId";        this.cmbEditContractorName.DisplayMember = "Name";         cmbEditContractorName.Enabled = true;         cmbEditContractorName.Focus();        // None of the following cause the ComboBox to display Contractor.Name        // The first entry in the ComboBox, which is a blank, is displayed        object myObject = cmbEditContractorName.SelectedItem = contractor;         System.Diagnostics.Trace.WriteLine("EditContractorDialog(): myObject: " + myObject.GetType()); // type is Contractor        System.Diagnostics.Trace.WriteLine("EditContractorDialog(): myObject: " + myObject); // myObject is the contractor        object myObject2 = cmbEditContractorName.SelectedText = contractor.Name;        System.Diagnostics.Trace.WriteLine("EditContractorDialog(): myObject2: " + myObject2.GetType()); // type is String        System.Diagnostics.Trace.WriteLine("EditContractorDialog(): myObject2: " + myObject2); // myObject2 is the contractor.Name     }}    

Answer 1

那是因为您需要从组合框本身的 DataSource 中获取要分配的对象引用。同样对于组合框，我建议您使用ObservableCollection<T>.

cmbEditContractorName.DataSource = new ObservableCollection<Type>(your List<Type>);

cmbEditContractorName.SelectedItem = ((ObservableCollection<Type>)cmbEditContractorName.DataSource).FirstOrDefault(c=> c.yourProperty = "something"); // this will select the first item meeting your condition

您的代码不起作用，因为您正在SelectedItem使用组合框中不存在的对象的引用分配属性DataSource。