关于网格数据绑定的问题
本文关键字:数据绑定 问题 网格 于网格 | 更新日期: 2023-09-27 17:50:12
我们的应用程序在一个特定的结构中生成一个巨大的结果列表。问题是,如果我想在DataGrid中显示它,我必须创建一个DataTable并将其设置为将使用内存的网格的数据源。因此,我创建了一个我创建的类(称为myRow)的BindingList,并且在myRow的结构中,我拥有我需要的所有字段,作为指向实际结果列表中的值的属性。但问题是,用户可以添加自定义列列表的结果;我不能动态地更改myRow的属性,我不想使用数据表(因为它将是我的实际结果的副本),如果我直接在dataGrid中创建自定义列并逐个单元设置它们的值,则内存中的网格的大小会非常高(我认为这是因为逐个单元设置值导致每个单元保存单元的属性,而不是更大的标准)。所以有人知道我如何创建一个类的行与使用属性作为列不同的策略,这样我就可以动态地设置在运行时列的数量?
我认为这可以通过使用TypeDescriptionProvider
来完成。
坏消息是:我以前从来没有这样做过,所以不能提供太多帮助
好消息是:我在这里找到了一个例子:DataGridView没有显示实现ICustomTypeDescriptor的对象的属性
//编辑
我使用代码(见上面的链接)来构建一个如何避免每个对象使用字典的示例…
public class myRow
{
//your data storage class ...
public string txt { get; set; }
public int id { get; set; }
}
public class MyView:ICustomTypeDescriptor
{//your extendable view class ...
private static PropertyDescriptorCollection props = null;
static MyView()
{
TypeDescriptionProvider defaultProvider = TypeDescriptor.GetProvider(typeof(MyView));
props = new PropertyDescriptorCollection(defaultProvider.GetTypeDescriptor(typeof(MyView)).GetProperties().Cast<PropertyDescriptor>().ToArray(), true);
}
public static void addProperty(string name, DataTable dt, Func<DataRow, object> getter, Action<DataRow, object> setter, Func<DataTable, MyView, DataRow> rowSelector, Type PropType)
{
List<PropertyDescriptor> tmp;
if (props != null) tmp = props.Cast<PropertyDescriptor>().ToList();
else tmp = new List<PropertyDescriptor>();
PropertyDescriptor pd = TypeDescriptor.CreateProperty(typeof(MyView), name, PropType, null);
pd = new MyViewPropertyDescriptor(pd, dt, getter, setter, rowSelector, PropType);
tmp.Add(pd);
props = new PropertyDescriptorCollection(tmp.ToArray(), true);
}
//the data storage obj this view is referencing
public myRow obj;
public string TXT { // view-member known at compile time
get { return obj.txt; }
set { obj.txt = value; }
}
internal class MyViewPropertyDescriptor : PropertyDescriptor
{ // an example property descriptor that can link to data in a DataTable ...
DataTable dt;
Func<DataRow, object> getter;
Action<DataRow, object> setter;
Func<DataTable, MyView, DataRow> rowSelector;
Type type;
public MyViewPropertyDescriptor(PropertyDescriptor descr, DataTable dt, Func<DataRow, object> getter, Action<DataRow, object> setter, Func<DataTable, MyView, DataRow> rowSelector, Type PropType)
: base(descr)
{
this.dt = dt; // storage for additional data referenced by this property
this.getter = getter; //a getter that will take a DataRow, and extract the property value
this.setter = setter; //a setter that will take a DataRow and a value
this.rowSelector = rowSelector;//a row selector ... takes a dataset and the view object and has to return the assiciated datarow
this.type = PropType; // the type of this property
}
public override object GetValue(object component)
{
// using row selector and getter to return the current value ... you should add errorhandling here
return getter(rowSelector(dt, (MyView)component));
}
public override void SetValue(object component, object value)
{ // the setter ... needs errorhandling too
setter(rowSelector(dt, (MyView)component), value);
}
public override void ResetValue(object component)
{
}
public override bool CanResetValue(object component)
{
return false;
}
public override bool ShouldSerializeValue(object component)
{
return false;
}
public override Type PropertyType
{
get { return type; }
}
public override bool IsReadOnly
{
get { return false; }
}
public override Type ComponentType
{
get { return typeof(MyView); }
}
}
ICustomTypeDescriptor defaultDescriptor = TypeDescriptor.GetProvider(typeof(MyView)).GetTypeDescriptor(typeof(MyView));
AttributeCollection ICustomTypeDescriptor.GetAttributes()
{
return defaultDescriptor.GetAttributes();
}
string ICustomTypeDescriptor.GetClassName()
{
return defaultDescriptor.GetClassName();
}
string ICustomTypeDescriptor.GetComponentName()
{
return defaultDescriptor.GetComponentName();
}
TypeConverter ICustomTypeDescriptor.GetConverter()
{
return defaultDescriptor.GetConverter();
}
EventDescriptor ICustomTypeDescriptor.GetDefaultEvent()
{
return defaultDescriptor.GetDefaultEvent();
}
PropertyDescriptor ICustomTypeDescriptor.GetDefaultProperty()
{
return defaultDescriptor.GetDefaultProperty();
}
object ICustomTypeDescriptor.GetEditor(Type editorBaseType)
{
return defaultDescriptor.GetEditor(editorBaseType);
}
EventDescriptorCollection ICustomTypeDescriptor.GetEvents(Attribute[] attributes)
{
return defaultDescriptor.GetEvents(attributes);
}
EventDescriptorCollection ICustomTypeDescriptor.GetEvents()
{
return defaultDescriptor.GetEvents();
}
PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties(Attribute[] attributes)
{
return props; // should really be filtered, but meh!
}
PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties()
{
return props;
}
object ICustomTypeDescriptor.GetPropertyOwner(PropertyDescriptor pd)
{
return this;
}
}
和一个使用这个的小例子…
private void button1_Click(object sender, EventArgs e)
{
if (dataGridView1.DataSource == null)
{
List<myRow> data = new List<myRow>();
data.Add(new myRow { id = 1, txt = "test 1" });
data.Add(new myRow { id = 2, txt = "test 2" });
data.Add(new myRow { id = 3, txt = "test 3" });
DataTable dt = new DataTable();
dt.Columns.Add("id", typeof(int));
dt.Columns.Add("additionalData1", typeof(int));
dt.Columns.Add("additionalData2", typeof(int));
Random rnd = new Random();
foreach (var item in data)
{
dt.Rows.Add(new object[] { item.id, rnd.Next(), rnd.Next() });
}
MyView.addProperty("additionalData1", dt, row => row["additionalData1"], (row, val) => row["additionalData1"] = val, (tab, v) => tab.Rows.OfType<DataRow>().First(x => x["id"].Equals(v.obj.id)), typeof(int));
MyView.addProperty("additionalData2", dt, row => row["additionalData2"], (row, val) => row["additionalData2"] = val, (tab, v) => tab.Rows.OfType<DataRow>().First(x => x["id"].Equals(v.obj.id)), typeof(int));
dataGridView1.DataSource = new BindingList<MyView>(data.Select(x => new MyView { obj = x }).ToList());
}
}
当然,你会想提供一个更好的rowSelector或替换数据表与哈希表或任何你想要的数据结构…举个例子