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。