如何修改组合框的选定文本？

Question

我是 UI WPF 的 C# 新手，我想设置 Combobox 的值？

cbx1.SelectedItem = "test 1";

这一行每次都显示为空（不例外）但 selectedItem 为空。

<telerik:RadComboBox Background="White" Foreground="{DynamicResource TitleBrush}"  x:Name="cbx1" AllowMultipleSelection="True" VerticalAlignment="Center" HorizontalAlignment="Right" Width="200" Grid.Row="1" Grid.Column="0" Margin="0,14,11,14" Height="22"/>

更新：

我觉得我的问题不够明确，我举个例子:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Collections.ObjectModel;
namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            ObservableCollection<Person> myPersonList = new ObservableCollection<Person>();

            Person personJobs = new Person("Steve", "Jobs");
            Person personGates = new Person("Bill", "Gates");

            myPersonList.Add(personJobs);

            myPersonList.Add(personGates);

            MyComboBox.ItemsSource = myPersonList;

            MyComboBox.SelectedItem = personGates;
        }
    }

    public class Person
    {

        public string FirstName { get; set; }

        public string LastName { get; set; }

        public Person(string firstName, string lastName)
        {
            FirstName = firstName;
            LastName = lastName;
        }
    }
}

在此代码中，如果 myCombobox.displayMemberPath = FirstName ，如何设置选定的 FirstName???

Answer 1

我没有 Teleriks Combobox，所以我在这里使用标准的 Combobox。您还应该知道 XAML 非常安静，它不会抛出异常，但您可能会在输出 window.

中发现一条错误消息

此示例遵循 MVVM 模式。这意味着您将在 PersonViewModel class（“视图模型”）中找到大部分代码，其中属性绑定到视图。（我在这里没有使用模型，但这可能是一个数据源 class）。 PersonViewModel 继承了 VMBase，它通知视图有关属性的更改。

因此，对于您的问题：我添加了属性“SelectedPerson”。此属性绑定到控件中的 SelectedItem。因此，每次您更改组合框中的项目时，SelectedPerson 将包含所选的 Person 对象。

我还添加了一个按钮“Select Steve”，它将在 PersonViewModel 中找到名字为“Steve”的 Person 对象，并将 SelectedPerson 设置为该对象。组合框将更改为“史蒂夫”。

Window1.xaml

  <Window x:Class="SO65149368.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:SO65149368"
        mc:Ignorable="d"
        Title="Window1" Height="450" Width="800">
    <StackPanel>
        <ComboBox Name="MyComboBox" Width="300" HorizontalAlignment="Left" Margin="5"
                  ItemsSource="{Binding myPersonList}"
                  DisplayMemberPath="FirstName"
                  SelectedItem="{Binding SelectedPerson, Mode=TwoWay}"/>
        <StackPanel Orientation="Horizontal">
            <Button x:Name="SelectSteve" Content="Select Steve" Click="SelectSteve_Click" 
   Margin="5"/>
        </StackPanel>
    </StackPanel>
  </Window>

Window1.xaml.cs

using System.Windows;

namespace SO65149368
{
    public partial class Window1 : Window
    {
        public PersonViewModel PersonViewModel = new PersonViewModel();
        public Window1()
        {
            DataContext = PersonViewModel;
            InitializeComponent();
        }

        private void SelectSteve_Click(object sender, RoutedEventArgs e)
        {
            PersonViewModel.SelectSteve();
        }
    }
}

PersonViewModel.cs

using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;

namespace SO65149368
{
    public class PersonViewModel : VMBase
    {
        public ObservableCollection<Person> myPersonList { get; } = new ObservableCollection<Person>();
        public PersonViewModel()
        {
            Person personJobs = new Person("Steve", "Jobs");
            Person personGates = new Person("Bill", "Gates");

            myPersonList.Add(personJobs);
            myPersonList.Add(personGates);

            SelectedPerson = personGates;
            //MyComboBox.ItemsSource = myPersonList;
            //MyComboBox.SelectedItem = personGates;
        }

        public Person SelectedPerson
        {
            get { return _selectedPerson; }
            set 
            {
                Set(ref _selectedPerson, value);
                Debug.WriteLine("Selected person: " + SelectedPerson.FirstName + " " + SelectedPerson.LastName);
            }
        }
        private Person _selectedPerson;

        public void SelectSteve()
        {
            SelectedPerson = myPersonList.FirstOrDefault(p => p.FirstName == "Steve");
        }
    }
}

VMBase.cs

using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace SO65149368
{
    public abstract class VMBase : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected bool Set<T>(ref T field, T newValue, [CallerMemberName] string propertyName = null)
        {
            if (!EqualityComparer<T>.Default.Equals(field, newValue))
            {
                field = newValue;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
                return true;
            }

            return false;
        }
    }
}

如何修改组合框的选定文本？

How I can modify the Selected text of Combobox?

c#

wpf

telerik