Question

我使用ViewModel中的属性为组合框设置了绑定。但是当我在设备上调试应用程序时，组合框的内容只是每个索引的模型名称，如LC_Points.Model.Grade。

要调试此问题，我已经完成了以下检查：

检查属性是否公开
检查列表不为空
检查VM中的正确绑定名称

有谁知道如何修复此绑定问题？

包含列表的ViewModel设置如下：

namespace LC_Points.ViewModel
{

    public class MainViewModel : ViewModelBase
    {

        /// <summary>
        /// Initializes a new instance of the MainViewModel class.
        /// </summary>
        public MainViewModel()
        {
            //call methods to initilise list data
            GetGradeTypes();
            GetSubjectTypes();

        }


        public List<Grade> grades { get; set; }
        public List<Grade> subjects { get; set; }

        public void GetGradeTypes()
        {
            List<Grade> gradeList = new List<Grade>();

            // Adding Grades to List
            gradeList.Add(new Grade { grade = "A1" });
            gradeList.Add(new Grade { grade = "A2" });
            gradeList.Add(new Grade { grade = "B1" });
            gradeList.Add(new Grade { grade = "B2" });
            gradeList.Add(new Grade { grade = "B3" });
            gradeList.Add(new Grade { grade = "C1" });
            gradeList.Add(new Grade { grade = "C2" });
            gradeList.Add(new Grade { grade = "C3" });
            gradeList.Add(new Grade { grade = "D1" });
            gradeList.Add(new Grade { grade = "D2" });
            gradeList.Add(new Grade { grade = "D3" });
            gradeList.Add(new Grade { grade = "E,F,NG" });
            gradeList.Add(new Grade { grade = "Pass" });
            gradeList.Add(new Grade { grade = "Merit" });
            gradeList.Add(new Grade { grade = "Distinction" });


            grades = gradeList;

        }


        public void GetSubjectTypes()
        {
            List<Grade> subjectList = new List<Grade>();

            // Adding Subjects to List
            subjectList.Add(new Grade { subject = "Accounting" });
            subjectList.Add(new Grade { subject = "Agricultural Economics" });
            subjectList.Add(new Grade { subject = "Agricultural Science" });
            subjectList.Add(new Grade { subject = "Ancient Greek" });
            subjectList.Add(new Grade { subject = "Applied Math" });
            subjectList.Add(new Grade { subject = "Arabic" });
            subjectList.Add(new Grade { subject = "Art" });
            subjectList.Add(new Grade { subject = "Artistic & Creative Group" });
            subjectList.Add(new Grade { subject = "Biology" });
            subjectList.Add(new Grade { subject = "Business" });
            subjectList.Add(new Grade { subject = "Business Group" });
            subjectList.Add(new Grade { subject = "Chemistry" });
            subjectList.Add(new Grade { subject = "Classical Studies" });
            subjectList.Add(new Grade { subject = "Construction Studies" });
            subjectList.Add(new Grade { subject = "Design & Comm Graphics" });
            subjectList.Add(new Grade { subject = "Economics" });
            subjectList.Add(new Grade { subject = "Engineering" });
            subjectList.Add(new Grade { subject = "English" });
            subjectList.Add(new Grade { subject = "French" });
            subjectList.Add(new Grade { subject = "Geography" });
            subjectList.Add(new Grade { subject = "German" });
            subjectList.Add(new Grade { subject = "Hebrew Studies" });
            subjectList.Add(new Grade { subject = "History" });
            subjectList.Add(new Grade { subject = "Home Economics" });
            subjectList.Add(new Grade { subject = "Irish" });
            subjectList.Add(new Grade { subject = "Italian" });
            subjectList.Add(new Grade { subject = "Japanese" });
            subjectList.Add(new Grade { subject = "Languages & Humanities" });
            subjectList.Add(new Grade { subject = "Latin" });
            subjectList.Add(new Grade { subject = "Link Modules" });
            subjectList.Add(new Grade { subject = "Mathematics" });
            subjectList.Add(new Grade { subject = "Music" });
            subjectList.Add(new Grade { subject = "Other Language" });
            subjectList.Add(new Grade { subject = "Physics" });
            subjectList.Add(new Grade { subject = "Physics & Chemistry" });
            subjectList.Add(new Grade { subject = "Practical Group" });
            subjectList.Add(new Grade { subject = "Religious Education" });
            subjectList.Add(new Grade { subject = "Russian" });
            subjectList.Add(new Grade { subject = "Science Group" });
            subjectList.Add(new Grade { subject = "Social Group" });
            subjectList.Add(new Grade { subject = "Spanish" });
            subjectList.Add(new Grade { subject = "Technology" });

            subjects = subjectList;

        }

    }
}

我在MainPage View中设置了这样的绑定：

<Page x:Class="LC_Points.MainPage"
      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:local="using:LC_Points"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
      DataContext="{Binding Source={StaticResource Locator}}"
      mc:Ignorable="d">



    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="40*" />
            <RowDefinition Height="20*" />
            <RowDefinition Height="30*" />
            <RowDefinition Height="30*" />
            <RowDefinition Height="20*" />
            <RowDefinition Height="20*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="4.5*" />
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>


        <ComboBox x:Name="subjectCmbBx"
                  Grid.Row="1"
                  Grid.ColumnSpan="2"
                  Width="174"
                  HorizontalAlignment="Left"
                  VerticalAlignment="Top"
                  ItemsSource="{Binding subjects}" />
        <ComboBox x:Name="gradeCmbBx"
                  Grid.Row="1"
                  Grid.Column="0"
                  Grid.ColumnSpan="2"
                  Width="70"
                  HorizontalAlignment="Right"
                  ItemsSource="{Binding grades}" />
    </Grid>

</Page>

调试期间的输出如下所示：

Debug combo box

Answer 1

除非您提供DisplayMemberPath（https://msdn.microsoft.com/en-us/library/system.windows.controls.itemscontrol.displaymemberpath%28v=vs.110%29.aspx），这是我建议您做的，否则它将使用提供的Grade::ToString()实现。所以，您也可以覆盖它。

Answer 2

您需要告诉ComboBox如何显示其项目。否则它只会在绑定项上调用ToString（）并显示一些不可思议的东西。

有三种方法可以获得合理的输出：

在DataObject上定义合理的ToString（）。这是一个好主意，即使你做其中一个，因为如果你没有另外设置辅助功能信息，讲述者会读这个。
在ComboBox上定义DisplayMemberPath以指向要显示的属性。

<ComboBox x:Name="subjectCmbBx"
          Grid.Row="1"
          Grid.ColumnSpan="2"
          Width="174"
          HorizontalAlignment="Left"
          VerticalAlignment="Top"
          DisplayMemberPath="Name"
          ItemsSource="{Binding subjects}" />

为ComboBox定义一个ItemTemplate，以完全控制每个项目的显示方式。这将允许显示绑定对象的多个属性，格式化以及比纯文本更好的UI。您可以通过右键单击设计器中的ComboBox并选择Edit Additional Templates.Edit Generated Items（ItemTemplate）...然后根据需要填写它来生成一个空模板：

<ComboBox x:Name="subjectCmbBx"
          Grid.Row="1"
          Grid.ColumnSpan="2"
          Width="174"
          HorizontalAlignment="Left"
          VerticalAlignment="Top"
          ItemsSource="{Binding subjects}" >
    <ComboBox.Resources>
        <DataTemplate x:Key="DataTemplate1">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Image Source="{Binding Picture}" Grid.Column="0" />
                <TextBlock Text="{Binding Name}" Grid.Column="1" />
            </Grid>
        </DataTemplate>
    </ComboBox.Resources>
    <ComboBox.ItemTemplate>
        <StaticResource ResourceKey="DataTemplate1"/>
    </ComboBox.ItemTemplate>
</ComboBox>

我建议＃1（作为辅助功能的最低要求）和大多数情况下的＃3。

绑定到ComboBox显示模型名称而不是属性内容

2 个答案: