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?

关于网格数据绑定的问题

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