在 WPF 中的 XAML 中设置 DataContext [英] Setting DataContext in XAML in WPF

问题描述

我有以下代码:

MainWindow.xaml

<Window x:Class="SampleApplication.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        DataContext="{Binding Employee}">
    <Grid>       
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition Width="200" />
        </Grid.ColumnDefinitions>

        <Label Grid.Row="0" Grid.Column="0" Content="ID:"/>
        <Label Grid.Row="1" Grid.Column="0" Content="Name:"/>
        <TextBox Grid.Column="1" Grid.Row="0" Margin="3" Text="{Binding EmpID}" />
        <TextBox Grid.Column="1" Grid.Row="1" Margin="3" Text="{Binding EmpName}" /> 
    </Grid>
</Window>

Employee.cs

namespace SampleApplication
{
    public class Employee
    {
        public Employee()
        {
            EmployeeDetails employeeDetails = new EmployeeDetails();
            employeeDetails.EmpID = 123;
            employeeDetails.EmpName = "ABC";
        }
    }

    public class EmployeeDetails
    {
        private int empID;
        public int EmpID
        {
            get
            {
                return empID;
            }
            set
            {
                empID = value;
            }
        }

        private string empName;
        public string EmpName
        {
            get
            {
                return empName;
            }
            set
            {
                empName = value;
            }
        }
    }
}

这是非常简单的代码，我只想将 Employee.cs 类中的 EmpID 和 EmpName 属性绑定到 MainWindow.xaml 中文本框的文本属性，但什么也没有当我运行代码时出现在我的这些文本框中.绑定对吗?

This is very simple code and I just want to bind the EmpID and EmpName properties in my Employee.cs class to Text properties of Textboxes in MainWindow.xaml but nothing is appearing in my these textboxes when I am running the code. Is the binding right?

推荐答案

此代码将始终失败.

正如所写，它说:在我的 DataContext 属性上查找名为Employee"的属性，并将其设置为 DataContext 属性".显然这是不对的.

As written, it says: "Look for a property named "Employee" on my DataContext property, and set it to the DataContext property". Clearly that isn't right.

为了让您的代码正常工作，请将您的窗口声明更改为:

To get your code to work, as is, change your window declaration to:

<Window x:Class="SampleApplication.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:SampleApplication"
    Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
   <local:Employee/>
</Window.DataContext>

这会声明一个新的 XAML 命名空间(本地)并将 DataContext 设置为 Employee 类的实例.这将导致您的绑定显示默认数据(来自您的构造函数).

This declares a new XAML namespace (local) and sets the DataContext to an instance of the Employee class. This will cause your bindings to display the default data (from your constructor).

然而，这极不可能是您真正想要的.相反，您应该有一个带有 Employee 属性的新类(称为 MainViewModel)，然后绑定到该属性，如下所示:

However, it is highly unlikely this is actually what you want. Instead, you should have a new class (call it MainViewModel) with an Employee property that you then bind to, like this:

public class MainViewModel
{
   public Employee MyEmployee { get; set; } //In reality this should utilize INotifyPropertyChanged!
}

现在您的 XAML 变为:

Now your XAML becomes:

<Window x:Class="SampleApplication.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:SampleApplication"
        Title="MainWindow" Height="350" Width="525">
    <Window.DataContext>
       <local:MainViewModel/>
    </Window.DataContext>
    ...
    <TextBox Grid.Column="1" Grid.Row="0" Margin="3" Text="{Binding MyEmployee.EmpID}" />
    <TextBox Grid.Column="1" Grid.Row="1" Margin="3" Text="{Binding MyEmployee.EmpName}" />

现在您可以添加其他属性(其他类型、名称)等.有关详细信息，请参阅 实现模型-视图-视图模型模式

Now you can add other properties (of other types, names), etc. For more information, see Implementing the Model-View-ViewModel Pattern

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