与记录结构(动态列和行)的双向DataGrid绑定
本文关键字:绑定 DataGrid 结构 记录 动态 | 更新日期: 2023-09-27 18:09:08
我有一个记录结构,我试图绑定到DataGrid
。基本上,我的列是由视图模型动态指定的。应该在网格单元格中显示(和编辑)的值必须使用每个记录(网格每行后面的视图模型)上的函数来检索。
我看着这个问题,它让我完成了一半。不幸的是,我不能使用DynamicObject
,因为记录上的属性是有名称空间的名称,因此不能用字符串表示。我尝试了一种变化,我把这个命名空间的名字转换成一个可绑定的字符串(用下划线替换所有非法字符),但似乎DynamicObject
每次我导航DataGrid
时都会调用TryGetMember
(即每次我滚动时都会调用每个单元格的函数)。这样的表现是不够好的。
这是我迄今为止所拥有的用于显示数据(即GetValue
):
public interface IDataSet
{
IEnumerable<IRecord> Records { get; }
IEnumerable<IProperty> PropertiesToDisplay { get; }
}
public interface IProperty
{
XName Name { get; }
}
public interface IRecord
{
IEnumerable<KeyValuePair<IProperty, object>> Values { get; set; }
object GetValue(IProperty property);
void SetValue(IProperty property, object value);
}
internal class SomeClass
{
DataGrid myGrid; // this is defined in the XAML
IDataSet viewModel; // this is the DataContext
private void BindToViewModelUsingConverter()
{
foreach (IProperty property in viewModel.PropertiesToDisplay)
{
Binding binding = new Binding();
binding.Converter = new ConvertMyDataConverter();
binding.ConverterParameter = property;
var column = new DataGridTextColumn
{
Header = property.Name.LocalName,
Binding = binding
};
myGrid.Columns.Add(column);
}
myGrid.ItemsSource = viewModel.Records;
}
}
internal class ConvertMyDataConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var record = value as IRecord;
var property = parameter as IProperty;
if (record != null && property != null)
{
return record.GetValue(property);
}
return DependencyProperty.UnsetValue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
// not sure what to do here, yet
throw new NotImplementedException();
}
}
上面的代码用于显示值。然而,当我尝试编辑值时,我得到一个异常:
**Two-way binding requires Path or XPath**
这是有意义的,因为即使在上面的转换器中,我也不确定我会在ConvertBack
函数中写什么,因为我希望源保持不变(因为我绑定到IRecord
并且已经调用了IRecord.SetValue
函数来更新数据)。然而,即使我能够在没有路径的情况下进行双向绑定,ConvertBack
似乎也不会给我IRecord
的引用。
我是不是漏掉了什么琐碎的东西?我不反对开发一个自定义控件,但是我想要一些关于如何解决这个问题的技巧/想法。
我使用ICustomTypeDescriptor
和ITypedList
解决了这个问题。而不是Records
是IEnumerable<IRecord>
,我做了一个自定义集合,实现IList<IRecord>
和ITypedList
。对于ITypedList
实现,我返回了包装IProperty
实现的属性描述符:
public interface IDataSet
{
TypedRecordsCollection Records { get; }
IEnumerable<IProperty> PropertiesToDisplay { get; }
}
public class TypedRecordsCollection : ObservableCollection<RecordViewModel>, ITypedList
{
private PropertyDescriptorCollection _properties;
public TypedRecordsCollection(IEnumerable<IRecord> records)
{
_properties = new PropertyDescriptorCollection(
PropertiesToDisplay
.Select(prop => new CustomPropertyDescriptor(prop))
.ToArray());
records.ForEach(rec => Items.Add(new RecordViewModel(rec, _properties)));
}
public PropertyDescriptorCollection GetItemProperties(PropertyDescriptor[] listAccessors)
{
return _properties;
}
}
public interface IRecordViewModel : ICustomTypeDescriptor
{
object GetCellValue(IProperty property);
void SetCellValue(IProperty property, object value);
}
public class RecordViewModel : CustomTypeDescriptor, IRecord
{
private IRecord _record;
private PropertyDescriptorCollection _properties;
public RecordViewModel(IRecord record, PropertyDescriptorCollection properties)
{
_record = record;
_properties = properties;
}
public object GetCellValue(IProperty property)
{
return _record.GetValue(property);
}
public void SetCellValue(IProperty property, object value)
{
_record.SetValue(property, value);
}
public override PropertyDescriptorCollection GetProperties()
{
return _properties;
}
}
public class CustomPropertyDescriptor : PropertyDescriptor
{
private IProperty _property;
public CustomPropertyDescriptor(IProperty property)
: base(GetCleanName(property.Name), new Attribute[0])
{
_property = property;
}
public override object GetValue(object component)
{
var recordViewModel = component as IRecordViewModel;
if (recordViewModel != null)
{
return recordViewModel.GetCellValue(_property);
}
return null;
}
public override void SetValue(object component, object value)
{
var recordViewModel = component as IRecordViewModel;
if (recordViewModel != null)
{
recordViewModel.SetCellValue(_property, value);
}
}
private static string GetCleanName(XName name)
{
// need to return a XAML bindable string.. aka no "{}" or ".", etc.
}
}
现在在我的XAML中,我可以将AutogenerateColumns
设置为true,并直接绑定到Records
属性,而不需要转换器。