MVVM数据网格组合框数据源未在选择时更新

Question

我在MVVM项目中有一个数据网格，它有两个ComboBox列。我有一个DataTable作为ItemsSource，还有一个ObservableObject Collection作为ComboBox项的源。有一个选定项的ObservableObject实例。

虽然我可以下拉并选择框中的项目，但我的问题是，当选择一个项目时，它不会用该选择更新DataTable记录。例如，如果在记录中我想将一列设置为"0"；"计算机"；在组合框中，稍后查看该记录中的值，它显示为一个空单元格，而不是Computer。

绑定SelectedItem，然后用新的选择和新记录更新基础DataTable，我做错了什么？

public class AddGroupObjectTypeModel : ObservableObject
{
#region Properties
private int iD;
public int ID
{
get
{
return iD;
}
set
{
if (iD != value)
{
iD = value;
OnPropertyChanged();
}
}
}
private string objType;
public string ObjType
{
get
{
return objType;
}
set
{
if (objType != value)
{
objType = value;
OnPropertyChanged();
}
}
}
#endregion
}

private readonly ObservableCollection<AddGroupObjectTypeModel> objectTypeTerms = new()
{
new AddGroupObjectTypeModel { ID = 1, ObjType = "User" },
new AddGroupObjectTypeModel { ID = 2, ObjType = "Group" },
new AddGroupObjectTypeModel { ID = 3, ObjType = "Computer" }
};
public IEnumerable<AddGroupObjectTypeModel> ObjectTypeTerms
{
get { return objectTypeTerms; }
}
private AddGroupObjectTypeModel selectedObjectTypeTerm = new();
public AddGroupObjectTypeModel SelectedObjectTypeTerm
{
get { return selectedObjectTypeTerm; }
set { selectedObjectTypeTerm = value; OnPropertyChanged(); }
}
private DataTable objectsDisplayTable;
public DataTable ObjectsDisplayTable
{
get { return objectsDisplayTable; }
set { objectsDisplayTable = value; OnPropertyChanged(); }
}
ObjectsDisplayTable = new("Temporary Table");
ObjectsDisplayTable.Columns.Add("ObjectName", typeof(String));
ObjectsDisplayTable.Columns.Add("OType", typeof(String));
ObjectsDisplayTable.Columns.Add("ODomain", typeof(String));

<DataGrid x:Name="ObjectsTable"
AutoGenerateColumns="False"
Grid.Row="1"
CanUserResizeColumns="True"
Margin="2,0,0,0" 
Style="{StaticResource ThemedDataGrid}"
BorderBrush="{x:Null}"
ItemsSource="{Binding ObjectsDisplayTable,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
HorizontalAlignment="Stretch" 
VerticalAlignment="Stretch"
CanUserAddRows="True"
SelectionMode="Single"
SelectionUnit="Cell" 
>
<DataGridTemplateColumn Header="Type"
x:Name="OType"
MinWidth="200"
>
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Path=DataContext.ObjectTypeTerms, RelativeSource={RelativeSource AncestorType=DataGrid}}"
DisplayMemberPath="ObjType"
SelectedItem="{Binding Path=DataContext.SelectedObjectTypeTerm.ObjType, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged,RelativeSource={RelativeSource AncestorType=DataGrid}}"
SelectedValue="{Binding Path=DataContext.SelectedObjectTypeTerm.ID, RelativeSource={RelativeSource AncestorType=DataGrid}}"
SelectedValuePath="ID"
SelectedIndex="0"
IsSynchronizedWithCurrentItem="false"
Style="{StaticResource ComboBoxTheme}"
/>
</DataTemplate>

Answer 1

您应该将ComboBox的SelectedValue属性绑定到要更新的DataTable的列：

<ComboBox ItemsSource="{Binding Path=DataContext.ObjectTypeTerms, RelativeSource={RelativeSource AncestorType=DataGrid}}"
DisplayMemberPath="ObjType"
SelectedValuePath="ObjType"
SelectedValue="{Binding OType, UpdateSourceTrigger=PropertyChanged}"
SelectedIndex="0"
Style="{StaticResource ComboBoxTheme}" />

同时绑定SelectedValue和SelectedItem是没有意义的。