从列表到对象的绑定 [英] Binding from List with Objects

问题描述

在此处输入代码

我希望该项目的XAML中定义的列类别中有一个字符串. "Id"和"Description"已成功显示在DataGrid上，但"Category"却没有.请参见下面的屏幕截图.

I expect a string in column category, which is defined in the XAML of this project. The "Id" and the "Description" are successfully displayed on the DataGrid but the "Category" is not. See Screenshot below.

<Grid>
    <DataGrid Name="view" AutoGenerateColumns="False" Margin="-4,0,4,0" >
        <DataGrid.Columns>

            <DataGridTextColumn Header="#" Binding="{Binding Id}" />

            <DataGridTemplateColumn Header="Category">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <Label Content="{Binding Category.Name}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>

            <DataGridTemplateColumn Header="Description">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <Label Content="{Binding Beschreibung}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
        </DataGrid.Columns>
    </DataGrid>
</Grid>

    public MainWindow()
    {
        DataContext = this;
        InitializeComponent();
        Start();
    }


    public void Start()
    {
        var payments = new List<Payment>();

        using (var dc = new DataContext())
        {
            payments = (from c in dc.Categories
                        join p in dc.Payments
                        on c.Id equals p.CategoryId
                        select p).ToList();
        }
        view.ItemsSource = payments;
    }
}

这是我的付款类别

    public partial class Payment
{
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }

    [Required]
    [StringLength(500)]
    public string Beschreibung { get; set; }

    public DateTime Datum { get; set; }

    public int Amount { get; set; }

    public int IsIncome { get; set; }

    public int CategoryId { get; set; }

    public virtual Category Category { get; set; }
}

这是我的类别课程

    public partial class Category
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public Category()
    {
        Payments = new HashSet<Payment>();
    }
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }

    [Required]
    [StringLength(500)]
    public string Name { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Payment> Payments { get; set; }
}

推荐答案

尝试更改此代码

payments = (from c in dc.Categories
    join p in dc.Payments
    on c.Id equals p.CategoryId
    select p)
    .ToList();

到

payments = (from c in dc.Categories
    join p in dc.Payments
    on c.Id equals p.CategoryId
    select p)
    .Include("Category")
    .ToList();

它将急切地从数据库中加载Category，它应该可以解决您的问题.

It will eagerly load Category from database and it should fix your problem.

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