Question

我正在玩WPF和LINQ，并坚持下面的一点，不知道如何显示单个记录，我发现的所有示例都显示如何显示列表，但不是单个记录。<登记/> 我准备了一个用户控件，它应该一次显示一条记录，在我的例子中是一个Customer，显示它的'Id，Given Name和Surname，这里是：

<UserControl x:Class="SportsClubsManagement.CustomersManagement.CustomerData"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="500">
    <Grid DataContext="Binding Customer">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Label Grid.Row="0" Grid.Column="0" Content="Id" Height="30" Width="70" />
        <TextBox Grid.Row="0" Grid.Column="1" Height="20" Width="70" Name="Id" Text="{Binding Path=Id}" />
        <Label Grid.Row="1" Grid.Column="0" Content="Given Name" Height="30" Width="70" />
        <TextBox Grid.Row="1" Grid.Column="1" Height="20" Width="70" Name="GivenName" Text="{Binding Path=GivenName}" />
        <Label Grid.Row="1" Grid.Column="2" Content="Surname" Height="30" Width="70" />
        <TextBox Grid.Row="1" Grid.Column="3" Height="20" Width="70" Name="Surname" Text="{Binding Path=Surname}" />
        <Button Grid.Row="2" Grid.Column="0" Content="New record" />
        <Button Grid.Row="2" Grid.Column="3" Content="Next record" />
        <Button Grid.Row="2" Grid.Column="2" Content="Prev record" />
    </Grid>
</UserControl>

我还创建了一个包含多个记录的表和一个代表客户的类，该客户也实现了INotifyPropertyChanged。

[Table(Name = "Customers")]
    public class Customer : INotifyPropertyChanged
    {
        #region Fields

        private String id;

        private String givenName;
        private String surname;

        #endregion
        #region Properties

        [Column(IsPrimaryKey=true, Storage="id", Name="Id")]
        public String Id
        {
            get { return this.id; }
        }

        [Column(Storage="givenName", Name="GivenName")]
        public String GivenName
        {
            get { return this.givenName; }
            set {
                if (this.givenName != value)
                {
                    this.givenName = value;
                    this.OnPropertyChanged("GivenName");
                }
            }
        }

        [Column(Storage="surname", Name="Surname")]
        public String Surname
        {
            get { return this.surname; }
            set {
                if (this.surname != value)
                {
                    this.surname = value;
                    this.OnPropertyChanged("Surname");
                }
            }
        }

        #endregion

        #region INotifyPropertyChanged Members" 

        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(String name)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }

        #endregion
    }

现在在用户控件背后的代码中，我有一个非常简单的代码连接到db并获取记录：

public partial class CustomerData : UserControl
    {

        private int curCustSeqNum;

        private Data.Customer customer;

        public Data.Customer Customer
        {
            get
            {
                return customer;
            }
            set
            {
                this.customer = value;
            }
        }

        private IQueryable<Data.Customer> custQuery;

        public CustomerData()
        {
            InitializeComponent();

            DataContext db = new DataContext(@"server=WIN-EL78137MUMS\SQLEXPRESS;database=PlayGround;integrated security=SSPI");

            // Get a typed table to run queries.
            Table<Data.Customer> Customers = db.GetTable<Data.Customer>();
            //db.Log = Console.Out;

            custQuery =
                from cust in Customers
                orderby cust.Id
                select cust;

            curCustSeqNum = 0;

            Customer = custQuery.Skip(curCustSeqNum).Take(1).First();

        }
    }

但是如何将文本框绑定到当前选定的客户？在定义资源等之后，您可以看到我的最后一次猜测。但每次我都会错过一些东西。我想知道如何在XAML和后面的代码中实现这一点。基本上之后，我可以使用curCustSeqNum跳到以下记录。

Answer 1

CustomerData没有实现INotifyPropertyChanged所以当你在构造函数中设置Customer时，xaml没有想法它已经改变了。

示例：

public partial class CustomerData : UserControl, INotifyPropertyChanged
{
    private int curCustSeqNum;
    private Data.Customer customer;
    private IQueryable<Data.Customer> custQuery;

    public Data.Customer Customer
    {
        get { return customer; }
        set { this.customer = value; OnPropertyChanged("Customer"); }
    }

    public CustomerData()
    {
        InitializeComponent();

        // set the datacontext
        DataContext = this;

        ................

        Customer = custQuery.Skip(curCustSeqNum).Take(1).First();
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(String name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

其他人也提到过，你对Grid上的DataContext绑定无效

 <Grid DataContext="Binding Customer">

应该是

 <Grid DataContext="{Binding Customer}">

Answer 2

通常，您在ViewModel中创建一个“CurrentItem”对象，您可以在其中初始化SelectionCommand。在您的情况下，您将在SelectionCommand上绑定您的“客户”，在该命令中您运行Customer.Get（id）命令以获取当前客户。然后，您可以将控件绑定到每个控件的字段的“CurrentCustomer”对象。

Answer 3

尝试将Datacontext设置为

DataContext="{Binding Path=Customer}"

我意识到道路是暗示的，但是我自己遇到了这个问题，这为我解决了这个问题。

绑定单个记录

3 个答案: