我正在构建一个 WPF 应用程序来管理存储在 SharePoint 列表中的学生数据库。我是使用 MVVM 的新手,并且已经阅读了一些教程。我已经成功地创建了一个 View 和模型,并设法将它绑定(bind)到一个数据网格控件。我想做的是根据组合框的输出更新 View 中的数据。
这是我的模型:
using System.ComponentModel;
namespace StudentManagement.Model
{
public class Student : INotifyPropertyChanged
{
private string _Title;
private string _FullName;
public string Title
{
get { return _Title; }
set
{
if (_Title != value)
{
_Title = value;
RaisePropertyChanged("Title");
}
}
}
public string FullName
{
get { return _FullName; }
set
{
if (_FullName != value)
{
_FullName = value;
RaisePropertyChanged("FullName");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
}
这是 View 模型:
using System.Collections.ObjectModel;
using StudentManagement.Model;
using SP = Microsoft.SharePoint.Client;
using StudentManagement.publicClasses;
namespace StudentManagement.ViewModel
{
public class StudentViewModel
{
public ObservableCollection<Student> Students { get; set; }
public void LoadStudents(string query)
{
ObservableCollection<Student> _students = new
ObservableCollection<Student>();
SP.ClientContext ctx = clientContext._clientContext;
SP.CamlQuery qry = new SP.CamlQuery();
qry.ViewXml = query;
SP.ListItemCollection splStudents =
ctx.Web.Lists.GetByTitle("Students").GetItems(qry);
ctx.Load(splStudents);
ctx.ExecuteQuery();
foreach (SP.ListItem s in splStudents)
{
_students.Add(new Student { Title = (string)s["Title"], FullName = (string)s["FullName"] });
}
Students = _students;
}
}
}
这是我的 XAML
<UserControl x:Class="StudentManagement.Views.StudentsView"
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"
xmlns:local="clr-namespace:StudentManagement.Views" >
<Grid>
<StackPanel HorizontalAlignment="Left" Width="200" >
<TextBox Name="txtSearch" AcceptsReturn="True" ></TextBox>
<ComboBox Name="cmbStatus" SelectionChanged="cmbStatus_SelectionChanged" SelectedIndex="0">
<ComboBoxItem>Active</ComboBoxItem>
<ComboBoxItem>Inquiring</ComboBoxItem>
<ComboBoxItem>Inactive</ComboBoxItem>
<ComboBoxItem>Monitoring</ComboBoxItem>
</ComboBox>
<DataGrid Name="dgStudentList" ItemsSource="{Binding Path=Students}" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Header="Name" Binding="{Binding Title, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="100"/>
<DataGridTextColumn Header="Parent" Binding="{Binding FullName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="100" />
</DataGrid.Columns>
</DataGrid>
</StackPanel>
</Grid>
</UserControl>
...以及 View 背后的代码:
using System.Windows.Controls;
using StudentManagement.ViewModel;
namespace StudentManagement.Views
{
/// <summary>
/// Interaction logic for StudentsView.xaml
/// </summary>
public partial class StudentsView : UserControl
{
private StudentViewModel _viewModel = new
StudentViewModel();
public StudentsView()
{
InitializeComponent();
DataContext = _viewModel;
}
private void cmbStatus_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
string combotext = ((sender as ComboBox).SelectedItem as ComboBoxItem).Content as string;
string qry = @"<View>
<Query>
<Where><Eq><FieldRef Name='Current_x0020_Status' /><Value Type='Choice'>" + combotext + @"</Value></Eq></Where>
</Query>
</View>";
_viewModel.LoadStudents(qry);
}
}
}
就目前而言,学生们在加载时就可以很好地加载到数据网格中。当事件 cmbStatus_SelectionChanged 触发时,我已经完成了测试,我可以看到 LoadStudents 函数触发并返回正确数量的条目,但数据网格上没有任何更新。
我确定这是一个菜鸟错误,我错过了一些基本的东西,但这个是我的头脑,我很感激任何指导。
最佳答案
由于StudentViewModel.LoadStudents()
更改 Students
的值属性, View 模型需要通知 View 这发生了变化。你可以通过 StudentViewModel
来做到这一点。实现INotifyPropertyChanged
(就像 Student
一样)。 DataGrid
将订阅 PropertyChanged
事件,并在该事件被触发时更新其内容。
关于c# - 当 ViewModel 改变时如何让 View 更新,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56060843/