具有复杂项目的列表的数据绑定

Question

I'm trying to bind a list of type User into a data grid with 2 columns.

class User:

public class User
    {

        private string username;
        private string password;
        private Object person;

        public User(string _username, string _password, Object _person=null)
        {
            username = _username;
            password = _password;
                person = _person;
        }

        public string UserName
        {
            get { return username; }
            set { username = value; }
        }
        public string Password
        {
            get { return password; }
            set { password = value; }
        }
        public Object Person
        {
            get { return person; }
            set { person = value; }
        }

main.xaml:

<DataGrid Name="UserGrid" ItemsSource="{Binding}">
        <DataGrid.Columns>
            <DataGridTextColumn Header="User name" Binding="{Binding UserName}"/>
            <DataGridTextColumn Header="Person" Binding="{Binding Person}"/>
       </DataGrid.Columns>
</DataGrid>

main.xaml.cs

UserGrid.DataContext = listOfUsers;

This code works fine! it binds a list of Users into the DataGrid. Now it's displaying the value of username and the value of person.

But i want to display an internal property of the Object person . Let's say that the object that called person is of type Food and has a property called taste .

How do i make the DataGrid display the value of username and the value of Person.taste ?

Answer 1

Depending on how you want to display the data, here are a few different things you can do (this isn't an exhaustive list):

1. Bind to Person.Food.taste directly.
2. Add a ToString() override to the Person class and return the string the way you want it to be displayed. You won't be able to edit it this way without doing extra work, but not sure if editing is a requirement.

3. Use a DataGridTemplateColumn to present the data in any custom way that you want to (and handle your own editing if needed). For example:

    <DataGridTemplateColumn Header="Person"> <DataGridTemplateColumn.CellTemplate> <DataTemplate DataType="{x:Type local:User}"> <!-- Put any template you want here --> <TextBlock Text="{Binding Person.Food.taste}" /> </DataTemplate> </DataGridTemplateColumn.CellTemplate> </DataGridTemplateColumn> 

Edit: Based on your follow-up, if you want to have a column display different data for different types of objects, then you will need to use the DataGridTemplateColumn I mentioned, setup up a DataTemplate for each type of data, and create a template selector to select the correct one. So, your column will look something like this:

<DataGridTemplateColumn Header="Rank">
    <DataGridTemplateColumn.CellTemplateSelector>
        <local:RankTemplateSelector>
            <local:RankTemplateSelector.EmployeeTemplate>
                <DataTemplate DataType="{x:Type local:Employee}">
                    <TextBlock Text="{Binding Rank}" />
                </DataTemplate>
            </local:RankTemplateSelector.EmployeeTemplate>
            <local:RankTemplateSelector.CustomerTemplate>
                <DataTemplate DataType="{x:Type local:Customer}">
                    <TextBlock Text="N/A" />
                </DataTemplate>
            </local:RankTemplateSelector.CustomerTemplate>
            <local:RankTemplateSelector.ClubMemberTemplate>
                <DataTemplate DataType="{x:Type local:ClubMember}">
                    <TextBlock Text="N/A" />
                </DataTemplate>
            </local:RankTemplateSelector.ClubMemberTemplate>
        </local:RankTemplateSelector>
    </DataGridTemplateColumn.CellTemplateSelector>
</DataGridTemplateColumn>

And your template selector will look something like this:

class RankTemplateSelector : DataTemplateSelector
{
    public DataTemplate EmployeeTemplate { get; set; }
    public DataTemplate CustomerTemplate { get; set; }
    public DataTemplate ClubMemberTemplate { get; set; }

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        if (item == null) return null;
        if (item is Employee) return EmployeeTemplate;
        if (item is Customer) return CustomerTemplate;
        if (item is ClubMember) return ClubMemberTemplate;
        throw new ArgumentException("The type of the item is not recognized", "item");
    }
}