网格数据绑定问题

Question

我们的应用程序以特定结构生成大量结果列表。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的 BindingList（称为 myRow），并且在 myRow 的结构中，我拥有我需要的所有字段作为指向中值的属性结果的实际列表。但问题是用户可以添加自定义列的结果列表；我无法动态更改 myRow 的属性，并且我不想使用 DataTable（因为它将与我的实际结果重复）并且如果我直接在 dataGrid 中创建自定义列和逐个单元格设置它们的值，内存中网格的大小非常高（我认为这是因为逐个单元格设置值会导致为每个单元格保存单元格的属性，而不是更大的标准）。那么有谁知道如何使用不同于使用属性作为列的策略创建一个行类，以便我可以在运行时动态设置列数？

Answer 1

我认为这可以通过使用TypeDescriptionProvider 来完成。

坏消息是：我以前从未这样做过，无法提供太多帮助

好消息是：我在这里找到了一个示例：DataGridView not showing properites of objects which implement ICustomTypeDescriptor

//编辑

我使用代码（参见上面的链接）构建了一个示例，如何避免每个对象的字典...

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;
    }

}

还有一个利用这个的小例子......

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，您会希望提供更好的 rowSelector 或将 DataTable 替换为 Hashtable 或您想要的任何数据结构......只是一个示例